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Reproductive & OB

Preterm Labor

PTL High-yield Verified · Sep 2026

Preterm labor is labor that starts before 37 completed weeks of pregnancy — contractions that produce cervical change after 20 weeks of gestation.

The disorder behind "tocolysis buys time, it does not stop labor," behind magnesium that is running for the baby's brain rather than the mother's uterus, behind indomethacin below 32 weeks and nifedipine above it, and behind the penicillin that has to be hung four hours before delivery to count.

What’s going wrong in the body

The normal physiology, where it fails, and why the body’s compensation backfires.

01 Four roads to the same door

Preterm birth is "delivery before 37 weeks gestation and after 20 weeks," and preterm labor is labor that begins in that window. Two halves of that definition do work. The lower bound matters: contractions before 20 weeks are not preterm labor. And cervical change matters: contractions alone are not the diagnosis. Preterm birth is subcategorized as extremely preterm, very preterm and late preterm — categories this page names without printing their week boundaries, because the cited chapter's sentence carries the category names and not the numbers. Worldwide incidence of preterm birth is about 10%, of which 40% to 45% begin as spontaneous preterm labor with intact membranes — so roughly half of preterm births take this route and the rest arrive by ruptured membranes, indicated delivery or another path. The disparity is quantified and stark: 5.5% incidence in non-Hispanic Black individuals versus 3.6% in non-Hispanic White individuals.

Four pathways converge on that door, and they are worth learning as four because each one explains a different part of the management plan. (1) Decidual inflammation from intrauterine infection, triggering prostaglandin and cytokine release. (2) Decidual hemorrhage and placental abruption. (3) Pathologic uterine distention. (4) Fetal or maternal stress activating placental corticotropin-releasing hormone. Pathway 1 is why a prostaglandin-synthesis inhibitor is a tocolytic at all — "COX inhibitors prevent the conversion of arachidonic acid to prostaglandins, which stimulate contractions." Pathway 2 is why bleeding matters twice: decidual hemorrhage can start labor, and placental abruption ends expectant management.

Where the membranes are involved, the mechanism is collagen. The amnion and chorion are joined "by the twelfth week of gestation by a strong yet flexible extra-cellular matrix comprised of various collagen types," and rupture "can arise from various causes, including membrane weakening, intraamniotic pressure, infection, and other stressors." The key sentence is that "inflammation can activate proteases that degrade collagen within the fetal membranes" — the same inflammatory pathway that starts contractions also dissolves the bag. One mechanism, two diagnoses, which is why preterm labor and preterm prelabor rupture of membranes share a page, a risk list and most of a management plan.

Four pathways, one final common chain. Notice where the treatment acts: not at the trigger, which is usually already irreversible, but at the last arrow, reducing what prematurity costs the newborn.

02 Making the diagnosis — two numbers that do not agree, and one test that only rules out

The diagnostic threshold is genuinely contested. The source's diagnostic list accepts "Regular contractions and cervical dilation of 3 cm or more," and "Spontaneous PTL is unlikely to resolve once the cervix reaches at least 3 cm. However, treatment also benefits patients who are at high risk of preterm delivery, even if they have not yet reached 3 cm dilation." The same list therefore also accepts "Regular contractions with demonstrated cervical change over time," or symptoms with a short cervix. The tocolysis literature defines continued contractions as 4 or more contractions over 20 minutes producing cervical change, and other thresholds exist. Name a contraction count only with its source. The usable teaching is that the diagnosis is contractions plus cervical change, and that a number is named only with its owner.

Fetal fibronectin earns its keep on the negative result — but it is not only a rule-out test. Quoted: "the primary utility of checking for fFN in cervicovaginal secretions is its negative predictive value; the absence of fFN is associated with a low risk of birth within 7 days." A positive result — 50 ng/mL or above on the qualitative assay — raises risk, "though the positive predictive value of this test is still relatively low," on its own. Combined with an intermediate cervical length, however, it has a defined rule-in role: a positive fibronectin with a cervix of 15 to 20 mm up to 30 mm marks high risk of birth within 7 days. So the accurate teaching is that a negative result is the more useful one, not that a positive result is meaningless. There is a nursing action buried in it: the swab must be obtained before any digital cervical exam, before blood exposure and away from recent intercourse — each of which the source names as a cause of false-positive results, which is why the sample "is best collected before any other pelvic assessments." Swab first, examine second — the order is the whole validity of the test.

Transvaginal cervical length supplies the numbers, and the stratification is conditional rather than a single cut-off. Normal is 35 to 48 mm, and 30 mm or more puts preterm birth risk under 5%. Between those and the floor, the source combines length with fibronectin: a symptomatic patient is at high risk of birth within 7 days if the cervix is under 15 to 20 mm regardless of the fibronectin result, or if it is an intermediate 15 to 20 mm up to 30 mm with a positive fibronectin. The same measurement drives an intervention: an ultrasound-indicated cerclage is considered where there is a prior spontaneous loss or preterm birth before 34 weeks and a cervical length under 25 mm before 24 weeks in the current singleton pregnancy. One distinction must not blur: "Cervical insufficiency is the inability of the cervix to retain the fetus in the absence of uterine contractions (ie, painless cervical dilatation) due to a functional or structural cervical defect," and "Cerclage placement may be indicated by a history of cervical insufficiency or by certain sonographic or physical exam findings in a current pregnancy" — the intervention is a stitch, not a tocolytic. It comes out when labor starts: "A cerclage should be removed with the onset of preterm labor, the development of sepsis, or within 48 hours of PPROM," because "if a cerclage is in place during labor, the suture will tear through the cervix as it dilates."

03 What the drugs are actually for — the 48-hour window

The single most misunderstood fact in obstetric nursing is on this page: tocolysis does not stop preterm labor. The sourced purpose is to "prolong gestation for two to seven days," particularly the critical 48-hour window, and "The WHO has shown that it is beneficial to delay delivery by up to 48 hours, allowing for antenatal corticosteroids to help fetal lung maturity in premature neonates," though "There have been publications that have questioned if tocolytics have benefits on major neonatal morbidity." Maintenance beyond 48 hours is unsupported for every class tried — beta-agonists, calcium channel blockers, cyclooxygenase inhibitors and magnesium — and "repeat tocolytic therapy is not recommended." A patient told "we are stopping your labor" has been told something the evidence does not support.

What the 48 hours buy is specific. Delaying delivery "by up to 48 hours" allows "for antenatal corticosteroids to help fetal lung maturity in premature neonates," and in the ALPS trial antenatal betamethasone "significantly reduced the risk of neonatal respiratory morbidity." That is the answer to every version of "why delay delivery." Alongside it runs magnesium sulfate for fetal neuroprotection, given within 24 hours of an early preterm birth to reduce cerebral palsy and severe intraventricular hemorrhage, and group B streptococcus prophylaxis, which needs at least four hours in the mother to protect the newborn. And the fourth thing the window buys is geography: tocolysis "is important to allow for additional time to be transferred to a tertiary care center," because those centres "will have better access to specialists as well as resources for handling the delivery of preterm infants."

The choice of tocolytic is decided by gestational age, and the crossover has a mechanism. Indomethacin is preferred before 32 weeks and is "contraindicated after 32 weeks of gestational age" because the ductus arteriosus becomes prostaglandin-sensitive later in gestation and the drug can close it prematurely. Nifedipine takes over later — it "has a better safety profile than other tocolytic medications and is often used for tocolysis, especially after 30 to 32 weeks of EGA," and "Recent literature has suggested that nifedipine is the best tocolytic agent because of better neonatal outcomes and fewer side effects." WHO 2022 sets the conditions: nifedipine tocolysis only when "Gestational age is accurately assessed to be between 24 weeks 0 days and 33 weeks 6 days" and "There is no evidence that tocolysis is contraindicated (such as vaginal bleeding, placental abruption or intrauterine infection)"; WHO 2015 adds that "tocolytics should not be used when there is any obstetric or medical contraindication to prolonging the pregnancy." Tocolysis is not open-ended in either direction: tocolytics are "associated with a higher risk of intrauterine infection before 34 weeks" in ruptured membranes, and "No significant maternal or neonatal benefit has been shown with tocolytics beyond benefits attributed to a complete course of corticosteroids."

The plan has four parallel limbs and a clock. The tocolytic is the least important of them: it exists to hold the door open for the other three, which are what actually change the newborn outcome.

04 When the membranes go first — latency, infection, and the four findings that end the wait

Prelabor rupture of membranes "occurs when the fetal membranes rupture before the onset of labor contractions"; before 37 weeks it is preterm PROM, which complicates about 1% of deliveries. Diagnosis starts with a sterile speculum, not a finger: "direct visualization of fluid leakage from the cervical os or gross pooling confirms the diagnosis." The supporting tests each have a catch. Ferning — dried amniotic fluid "forms a crystalized pattern that appears like branches of a fern tree" — is confounded by cervical mucus, which ferns "in thick linear bands." Nitrazine rests on amniotic fluid pH of 7 to 7.4 against normal vaginal secretions of 3.8 to 4, but "false-positive pH tests… are common." The commercial assays for placental alpha microglobulin-1 and insulin-like growth factor binding protein-1 run at 95% to 99% sensitivity against about 85% for the conventional bedside methods.

Then comes the rule that governs the rest of the admission. "Digital examinations increase the risk of intraamniotic infection in patients with ROM; digital examinations to assess cervical dilation, effacement, and station should be avoided unless delivery appears imminent or the patient appears to be in active labor." Independently, "multiple vaginal exams post rupture of membranes" appear on the chorioamnionitis risk list. This is an iatrogenic risk factor that the team controls entirely.

Expectant management before 34 weeks "can be considered in the absence of contraindications to ongoing pregnancy," and the contraindications are four findings that end it immediately: intraamniotic infection, placental abruption, cord prolapse, and nonreassuring fetal status. Infection surveillance is clinical, not laboratory: assess for fever, uterine tenderness, foul-smelling discharge and fetal tachycardia, and understand that "in the absence of clinical findings… an elevated white blood count is nonspecific" — antenatal steroids raise it too. Before viability the conversation changes character entirely: maternal risks of expectant management include "potentially severe infection, hemorrhage, and death," one study found composite maternal morbidity of 60% with expectant management versus 33% with abortion care, and the sourced timeline is unforgiving — "the median interval from PPROM to the first signs of infection was 5 days; the median time from infection diagnosis to death was only 18 hours."

Ruptured membranes start two clocks at once, latency and infection, and the whole admission is a race between them. Surveillance is clinical: temperature, fetal heart rate, uterine tenderness and discharge; a white cell count is nonspecific on its own.

Causes & risk factors

Modifiable factors are teaching targets — the patient can act on them.

Prior preterm birth — the anchor risk factor. It is the entry criterion for both the ultrasound-indicated cerclage decision and the progesterone decision, so it changes management rather than only estimating risk Shortened cervical length. Normal is 35 to 48 mm and risk is under 5% at 30 mm or more; under 15 to 20 mm is high risk regardless of fibronectin, and an intermediate length with a positive fibronectin is high risk too. Under 25 mm before 24 weeks with a qualifying history is a cerclage threshold Intrauterine infection — pathway 1, the commonest driver, and the finding that converts expectant management into delivery modifiable Uterine overdistention — pathway 3 Placental complications — decidual hemorrhage is pathway 2 Maternal hypertensive disorders modifiable Substance use — a named risk factor for spontaneous preterm labor, alongside poor nutrition, suboptimal prenatal care and extremes of maternal age, and the clearest modifiable lever a patient holds modifiable For ruptured membranes specifically — a history of PROM, short cervical length and certain lifestyle factors; sterile inflammation from bleeding or tobacco use may also weaken the membranes Multiple vaginal examinations after rupture — an iatrogenic risk factor for chorioamnionitis that the team controls entirely modifiable A documented disparity, not an explanation: 5.5% incidence in non-Hispanic Black individuals versus 3.6% in non-Hispanic White individuals, with rupture of membranes occurring at twice the rate and recurring more than six times as often

Signs & symptoms

Each finding tied to the mechanism that produces it — and the triage it calls for.

Contractions every 10 minutes or more often early Hold & notify
Why: The patient-facing warning sign, quoted from the teaching list. Regular contractions are half the diagnosis; the other half is cervical change, which only an examination can supply. The instruction that goes with the list is to contact the provider.
Low, dull backache, or cramps that feel like menstrual cramps early Hold & notify
Why: Both are on the sourced warning-sign list and both are routinely dismissed by patients as normal pregnancy discomfort. They are on the list precisely because they do not feel like labor.
Feeling of pressure in the pelvis early Hold & notify
Why: On the same warning-sign list. It reflects descent and cervical change rather than contraction pain, which is why it can be the only symptom a patient has.
Abdominal cramps with or without diarrhea early Hold & notify
Why: The last item on the sourced warning list, and the one most often attributed to something eaten. Prostaglandin release acts on gut smooth muscle as well as myometrium.
Leaking fluid from the vagina — at any point in pregnancy Report immediately
Why: Quoted teaching: patients "should be instructed to present for evaluation if they ever experience leakage of fluid during pregnancy," because rupture of membranes must be ruled out given "the increasing risk of complications associated with a delayed diagnosis." Rupture starts the latency clock and the infection clock together.
Vaginal bleeding with contractions Report immediately
Why: Raises decidual hemorrhage and abruption, which is pathway 2. It changes the differential and belongs to the placenta-previa-abruption page's workup.
Regular contractions with documented cervical change Report immediately
Why: The diagnosis itself — "Regular contractions with demonstrated cervical change over time," or "Regular contractions and cervical dilation of 3 cm or more." It is an emergency evaluation because the intervention window is measured in hours and the steroid course needs 24 to 48 of them.
Cervical change without contractions (possible cervical insufficiency) Report immediately
Why: Think of cervical insufficiency — a separate etiology of preterm birth, for which "Cerclage placement may be indicated by a history of cervical insufficiency or by certain sonographic or physical exam findings in a current pregnancy." A tocolytic treats the wrong problem.
Maternal fever with fetal tachycardia, uterine tenderness, or purulent or foul-smelling discharge Report immediately
Why: The intraamniotic infection set: fever, uterine tenderness, foul-smelling discharge and fetal tachycardia (a fetal heart rate above 160 beats/min in the clinical chorioamnionitis criteria). Infection converts expectant management into delivery, and tocolytics carry a higher risk of intrauterine infection before 34 weeks.
A rise in maternal temperature during expectant management, even without other signs early Hold & notify
Why: Chorioamnionitis "presents as a febrile illness." Temperature is the surveillance instrument during the wait, which is why it is charted on a schedule rather than on symptoms.
Late decelerations, or a Category III tracing Report immediately
Why: Late decelerations and a Category III tracing signal a fetus in trouble — see Placenta Previa & Abruption for fetal heart rate categories. Nonreassuring fetal status is one of the four findings that end expectant management.
Umbilical cord prolapse after rupture of membranes Report immediately
Why: Cord prolapse is one of the four contraindications to continuing the pregnancy, and it ends expectant management immediately. It is a mechanical emergency with no medical management.

Diagnostics

Test In this disorder Normal
Fetal fibronectin Collection sequence is the test's validity: obtain it before any digital cervical exam, before blood exposure and away from recent intercourse, each of which "can all lead to false-positive results." Swab first, examine second. A positive result does not commit anyone to delivery; a negative one buys real reassurance Best used for its negative result. "The primary utility… is its negative predictive value; the absence of fFN is associated with a low risk of birth within 7 days." Positive is 50 ng/mL or above, which raises risk, "though the positive predictive value of this test is still relatively low," alone — though with an intermediate cervical length it does rule in high risk of birth within 7 days StatPearls, Preterm Labor —
Transvaginal cervical length The same number drives an intervention: ultrasound-indicated cerclage is considered with a prior spontaneous loss or preterm birth before 34 weeks plus a cervical length under 25 mm before 24 weeks in a singleton pregnancy Normal 35 to 48 mm, with a preterm birth risk under 5% at 30 mm or more. Risk is stratified with fibronectin rather than by length alone: under 15 to 20 mm is high risk for birth within 7 days regardless of the fibronectin result, and an intermediate length of 15 to 20 mm up to 30 mm with a positive fibronectin is also high risk StatPearls, Preterm Labor; cerclage threshold from StatPearls, Cervical Cerclage Most predictive before 34 weeks
Diagnosis of ruptured membranes No digital examination. Quoted: digital exams "increase the risk of intraamniotic infection in patients with ROM; digital examinations… should be avoided unless delivery appears imminent or the patient appears to be in active labor." Sterile speculum examination first. "Direct visualization of fluid leakage from the cervical os or gross pooling confirms the diagnosis" — pooling being "the rapid collection of amniotic fluid in the lower blade of the speculum" StatPearls, Preterm and Term Prelabor Rupture of Membranes —
Ferning and nitrazine Both have specific confounders. Cervical mucus also ferns, but "in thick linear bands secondary to its stringlike macroscopic structure." And "false-positive pH tests… are common, as multiple other causes of abnormally high vaginal pH may be present." Neither test is used alone to overturn a clinical picture Ferning: dried amniotic fluid "forms a crystalized pattern that appears like branches of a fern tree." Nitrazine: amniotic fluid pH is 7 to 7.4, against normal pregnancy vaginal secretions of 3.8 to 4 StatPearls, Preterm and Term Prelabor Rupture of Membranes —
Commercial amniotic protein assays These outperform ferning and nitrazine, which is worth knowing when a conventional test is negative in a patient who is convincingly leaking fluid. Ultrasound is also recommended to assess amniotic fluid volume, since oligohydramnios is often seen Detect placental alpha microglobulin-1 or insulin-like growth factor binding protein-1. Sensitivity about 95% to 99% StatPearls, Preterm and Term Prelabor Rupture of Membranes Conventional bedside methods run at about 85%
White blood cell count and inflammatory markers Antenatal corticosteroids also raise the white count, so a rise after a betamethasone dose is expected rather than alarming. The diagnosis of intraamniotic infection is made from fever, fetal tachycardia, uterine tenderness and discharge Not an infection test in this setting. "In the absence of clinical findings suggesting intraamniotic infection… an elevated white blood count is nonspecific," and antenatal steroids raise it independently StatPearls, Preterm and Term Prelabor Rupture of Membranes —
Group B streptococcus rectovaginal culture The collision with this page is the point: a patient in preterm labor at 30 weeks has not reached the screening window. That is exactly why unknown status plus preterm delivery before 37 weeks is itself an indication for prophylaxis. Penicillin-allergy regimens belong to the prescriber and the class page, but the specimen matters: the GBS sample should state the penicillin allergy, and for a patient at high risk of anaphylaxis to penicillin it should request clindamycin susceptibility testing, because 20% to 30% of GBS isolates are clindamycin resistant. Routine screening culture between 36 0/7 and 37 6/7 weeks of gestation; a positive culture is an indication for intrapartum antibiotic prophylaxis StatPearls, Streptococcus Group B (screening window and indications) —
Continuous fetal heart-rate monitoring In ruptured membranes fetal well-being "is typically accomplished with cardiotocographic monitoring and a biophysical profile." Fetal tachycardia (above 160 beats/min, one of the clinical chorioamnionitis criteria alongside maternal fever) is read here as an infection sign, not only a tracing finding. The category meanings, the variability bands and the deceleration meanings are owned by the placenta-previa-abruption page — follow the link rather than learning them twice Continuous cardiotocography monitors fetal well-being and contraction patterns during preterm labor; moderate variability or accelerations are reassuring NICHD three-tier system — the placenta-previa-abruption page cites the monitoring chapter and owns this table —
Assessment for intraamniotic infection This is a clinical assessment run on a schedule, not a laboratory diagnosis. A rise in maternal temperature is the instrument that starts it, and the white cell count explicitly does not: it is "nonspecific" absent clinical findings, and antenatal steroids raise it independently. A separate chorioamnionitis literature adds a two-tier fever rule and a named antibiotic regimen; neither is carried here, because this page does not cite that chapter The sourced sign set is fever, an elevated white cell count, uterine tenderness, abdominal pain, foul-smelling vaginal discharge, and fetal and maternal tachycardia StatPearls, Preterm and Term Prelabor Rupture of Membranes —

Complications

Black-box warning — most severe: ■ Intraamniotic infection and maternal sepsis Report immediately
Maternal complications of ruptured membranes are "intrauterine infection; sepsis; placental abruption; antenatal, intrapartum, and postpartum hemorrhage; death." Heralding cues: fever, fetal tachycardia, uterine tenderness, foul-smelling discharge.
The timeline in previable rupture is the one that should end any casual framing of expectant management: "the median interval from PPROM to the first signs of infection was 5 days; the median time from infection diagnosis to death was only 18 hours." Composite maternal morbidity ran at 60% with expectant management versus 33% with abortion care, and the Society for Maternal-Fetal Medicine recommends individualized counselling about maternal and fetal risks and offering abortion care in previable and periviable rupture. Established intraamniotic infection is treated with broad intravenous antibiotics and delivery; the specific regimen sits in a chorioamnionitis literature this page does not cite, so no drug names are given here. Neonatal consequences include cerebral palsy, respiratory distress syndrome, bronchopulmonary dysplasia, neonatal sepsis and death; maternal ones add pelvic infection, postpartum hemorrhage and operative delivery.
Warning: The four findings that end expectant management Report immediately
Nonreassuring fetal status, intraamniotic infection, placental abruption, and prolapsed umbilical cord. Any one of them converts a watching plan into a delivery plan immediately.
Learning these as a set is more useful than learning them separately, because expectant management in early preterm rupture "can be considered in the absence of contraindications to ongoing pregnancy," and the whole discipline of the admission is knowing what cancels it. Latency is finite in any case: in ruptured membranes before term, birth within 7 days occurs in "at least 50%" of cases, "although rare, cessation of fluid leakage with restoration of normal amniotic fluid volume and favorable outcomes is possible."
Warning: Prematurity itself — what the 48 hours are bought for Report immediately
Respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, retinopathy of prematurity, hypothermia, glucose and electrolyte abnormalities, failure to thrive, neonatal sepsis and death.
Antenatal corticosteroids "help fetal lung maturity," and in the ALPS trial they "significantly reduced the risk of neonatal respiratory morbidity" — which is the answer to "why delay delivery for 48 hours." Magnesium adds another target, reducing cerebral palsy and severe intraventricular hemorrhage when given within 24 hours of early preterm birth. Transfer is a treatment too: tocolysis buys "additional time to be transferred to a tertiary care center," and "Neonatal and anesthesia teams should also be informed so they can be aware of an upcoming preterm delivery."
Caution: Prolonged oligohydramnios
Two complications specific to sustained low fluid: pulmonary hypoplasia, and limb contractures and skeletal deformities.
This is why amniotic fluid volume is followed on serial ultrasound rather than checked once, and why the assessment during expectant management is not only a temperature chart. Amniotic fluid is a mechanical requirement for lung development and for limb positioning, so the harm accumulates with time rather than arriving as an event. In previable rupture the outcome data are correspondingly poor: in one cohort 52 of 86 patients with previable rupture delivered before 24 weeks, and only 23 neonates survived to discharge.
Caution: Iatrogenic harms the team controls
Repeated digital examinations after rupture, indomethacin continued past 32 weeks, and intracervical catheters for induction after rupture.
Each is sourced as a specific harm rather than a general caution. "Multiple vaginal exams post rupture of membranes" are on the chorioamnionitis risk list. Indomethacin after 32 weeks risks premature ductus arteriosus closure, along with oligohydramnios, gastric perforation and pulmonary hypertension. Intracervical catheters "should be avoided in patients with ruptured membranes, as they have been shown to nearly double the risk of intraamniotic infection" compared with pharmacologic induction.

Medications for this condition

Why each class is prescribed here — every card links to its full pharmacology page.

Corticosteroids First-line
Endocrine · prednisone

Antenatal corticosteroids are the reason tocolysis exists. The regimen and doses are ordered by the provider; the window is where the sources speak. The World Health Organization "recommends antenatal corticosteroids from 24 to 34 weeks EGA, including patients with PPROM, multifetal gestations, hypertensive disorders, or fetal growth restriction." Between 34 and 36 6/7 weeks sources differ: the Society for Maternal-Fetal Medicine offers a single course to patients meeting the ALPS trial criteria, WAPM-PMF suggests a 34 0/7-week cutoff, the Royal College of Obstetricians and Gynaecologists recommends offering steroids up until 34 6/7 weeks, and the World Health Organization recommends them from 24 to 34 weeks and advises against them before a planned cesarean between 34 and 36 6/7 weeks. A rescue course "may consist of either a standard 48-hour regimen described above or a single dose of betamethasone." Two contraindications belong with the late-preterm course specifically, and both collide with material elsewhere on this page. The Society for Maternal-Fetal Medicine recommends "against the use of antenatal steroids in late preterm patients with pregestational diabetes mellitus due to the risk of neonatal hypoglycemia," and the World Health Organization advises "against therapy for individuals with chorioamnionitis." So the finding that ends expectant management also withdraws the steroid, and a patient with pregestational diabetes does not get the late-preterm course. The WHO window explicitly includes patients with PPROM. What the drug buys, in the WHO evidence summary: "a 32% reduction in neonatal deaths," RDS "reduced by 35%," and "a reduction in the occurrence of cerebroventricular haemorrhage … and necrotizing enterocolitis." One practical consequence for the nurse reading labs: steroids raise the white cell count, so a rise after a dose is expected. Systemic corticosteroid pharmacology and adverse effects belong to the class page.
Magnesium Sulfate (Obstetric) First-line High-alert
Reproductive & OB

Magnesium is running for the baby's brain, not to stop the labor — and that sentence is the most testable thing on this page. The sourced role: "magnesium sulfate provides neuroprotection for the neonate" when given within 24 hours of an early preterm birth, reducing cerebral palsy risk and severe intraventricular hemorrhage. The tocolytic claim is explicitly negative: "The magnesium sulfate is used for neuroprotection and studies have failed to demonstrate its effectiveness in pregnancy prolongation in the setting of preterm labor." Thresholds differ by source: "The WHO strongly recommends magnesium sulfate for women at risk of imminent PTB before 32 weeks"; American guidelines recommend it "between viability and 31 6/7 weeks gestation"; and a 2024 Cochrane review found benefit "when given to patients at imminent risk of PTB before 34 weeks EGA." Two cautions travel with the drug: it requires renal dosing and is contraindicated in myasthenia gravis, with adverse effects of flushing, nausea, reduced deep tendon reflexes, blurred vision and reduced cardiac contractility. One interaction is a nursing safety rule: magnesium is "not advised… in conjunction with calcium channel blockers, unless for neuroprotection, due to the risk of maternal respiratory depression" — so magnesium plus nifedipine is a combination to question out loud. Remember that this same drug has three different obstetric indications and the nurse should always know which one is running: seizure prophylaxis in preeclampsia, neuroprotection here, and tocolysis, which the evidence does not support. The toxicity ladder, serum bands, stop rules and calcium gluconate antidote are owned by the preeclampsia page — follow the link rather than restating them.
NSAIDs
Musculoskeletal · ibuprofen

Indomethacin is the tocolytic below 32 weeks, and the disorder-side reason is mechanistic: the inflammatory pathway that starts preterm labor runs through prostaglandins, and "COX inhibitors prevent the conversion of arachidonic acid to prostaglandins, which stimulate contractions." The hard limit is the fact to carry: it is "contraindicated after 32 weeks of gestational age," because the ductus arteriosus becomes prostaglandin-sensitive later in gestation and the drug can close it prematurely. Its use is limited to 48 hours in any case. The fetal adverse effects are specific and named — "premature closure of the ductus arteriosus," and "Other fetal effects from indomethacin include oligohydramnios, gastric perforation, and pulmonary hypertension" — and the maternal ones are gastrointestinal: it increases "the rate of ulcer formation," and prostaglandin loss "increases the prevalence of mucosal injury and gastrointestinal bleeding." Contraindications are "bleeding disorders, gastritis, aspirin hypersensitivity, and hepatic impairment." The gestational-age split with nifedipine is the whole teaching point, and continuing indomethacin past 32 weeks is listed as an iatrogenic precipitant of deterioration rather than a minor protocol drift. General NSAID pharmacology belongs to the class page.
Calcium Channel Blockers
Cardiovascular · amlodipine

Nifedipine "is often used for tocolysis, especially after 30 to 32 weeks of EGA." "Calcium channel blockers specifically work on T-type calcium channels by inhibiting the entry of calcium into the uterine smooth muscle," and "The lack of free calcium directly affects the ability of the calcium-calmodulin activation of myosin light chain kinases" — no calcium, no cross-bridge cycling, no contraction. The preterm-labor source notes nifedipine "has a better safety profile than other tocolytic medications." Recent literature suggests it offers "better neonatal outcomes and fewer side effects" than the alternatives. The nursing consequence is a single parameter: maternal hypotension. Maternal adverse effects are flushing, headache, dizziness, nausea and hypotension; "Studies have shown no fetal risks with nifedipine use for the management of preterm labor"; and "Women who have documented hypotension and other cardiac conditions should use nifedipine with great caution" — so blood pressure is what gets monitored around each dose. And the magnesium interaction applies here, since these two drugs are the pairing the warning is about. Calcium channel blocker pharmacology otherwise belongs to the class page.
Penicillins First-line
Immune / Anti-infective · amoxicillin

Penicillin G is first-line for group B streptococcus intrapartum prophylaxis, and the timing is the nursing fact. "Prophylaxis with a beta-lactam antibiotic, preferably penicillin, administered 4 or more hours before delivery, provides highly effective protection against early-onset GBS disease." The regimen is 5 million units as the initial dose, then 2.5 to 3 million units every 4 hours until delivery — which is why the first dose is hung the moment preterm labor is diagnosed rather than after the cervical check. Indications are worth learning as a list: a positive screening culture at 36 0/7 to 37 6/7 weeks, GBS bacteriuria at any point in the current pregnancy, a previous infant with invasive GBS disease, and, when status is unknown, preterm delivery before 37 weeks, membrane rupture for 18 hours or more, an intrapartum temperature of 100.4 °F or higher, or a positive intrapartum NAAT. Ampicillin — a 2 g intravenous loading dose, then 1 g every 4 hours until delivery — is the alternative. With a penicillin allergy, the regimen belongs to the prescriber and the class page. Why this matters so much here: GBS colonization "affects up to one-third of healthy women," and screening with intrapartum prophylaxis cut early-onset neonatal disease from 1.7 cases per 1,000 live births in the early 1990s to 0.22 in 2017. Penicillin pharmacology and allergy cross-reactivity belong to the class page.

Beyond medications

  • Say what tocolysis is for, in the words the evidence supports. It is "intended to prolong gestation for two to seven days," with the demonstrated benefit being the 48-hour window that allows corticosteroids to work. Maintenance is not supported for any class — beta-agonists, calcium channel blockers, cyclooxygenase inhibitors or magnesium — and "repeat tocolytic therapy is not recommended." Telling a patient "we are stopping your labor" is telling her something the sources do not support.
  • Drug-specific tocolytic cautions, as a set: indomethacin "is also contraindicated after 32 weeks of gestational age because of premature closure of the ductus arteriosus"; "Women who have documented hypotension and other cardiac conditions should use nifedipine with great caution"; magnesium "is contraindicated in patients with myasthenia gravis"; and magnesium with a calcium channel blocker is "not advised… unless for neuroprotection, due to the risk of maternal respiratory depression." StatPearls also lists relative contraindications, among them "mild abruptio placentae, stable placenta previa, and intrauterine growth restriction," and notes "there is no beneficial delay in delivery with tocolytics for patients with symptomatic abnormal placentation." A Brazilian multicenter study notes in its background that tocolytics are considered only when there are no contraindications such as nonreassuring fetal status, severe fetal growth restriction, intra-amniotic infection, or lethal fetal anomalies, or complicated maternal illness. The provider owns the decision about whether tocolysis is used at all.
  • Terbutaline is a rescue agent, not a tocolysis regimen. It carries an FDA boxed warning against injectable terbutaline for "prolonged preterm labor-management (over 72 hours)" because of maternal cardiac complications from beta-1 activity, with arrhythmias, tachycardia, hypotension, nausea and vomiting on the maternal side and tachycardia on the fetal side. The only dose the fetched source supplies is for external cephalic version. Atosiban is not a US option — an oxytocin-receptor antagonist approved in Europe in 2000 and not FDA-approved — which is context for why US tocolysis means indomethacin or nifedipine.
  • Rupture of membranes, managed by band. Early preterm, 24 0/7 to 33 6/7 weeks: expectant management "in the absence of contraindications to ongoing pregnancy," with steroids, latency antibiotics and magnesium for neuroprotection. Late preterm, 34 0/7 to 36 6/7: "Immediate delivery is indicated if the patient is GBS-positive"; if "GBS negative or unknown, expectant management may be considered until 37 weeks." Term, 37 weeks or more: "immediately moving toward delivery… is associated with better maternal and fetal outcomes compared to expectant management."
  • Latency antibiotics in expectant PPROM management. "Latency antibiotics are indicated in patients with PPROM," and in expectant management they "can be considered as early as 20 0/7 weeks gestation." WHO: "Erythromycin is recommended as the antibiotic of choice for prophylaxis in women with preterm prelabour rupture of membranes," and "The use of a combination of amoxicillin and clavulanic acid (“co-amoxiclav”) is not recommended" — ORACLE I showed "that erythromycin lessens the risk of necrotizing enterocolitis (NEC) in the newborn compared to co-amoxiclav." Antibiotics are not routine in preterm labor with intact membranes and no signs of infection. The regimen tested in the NICHD Maternal-Fetal Medicine Units Network trial (PPROM at 24 to 32 weeks) was IV ampicillin plus erythromycin for 48 hours, then oral amoxicillin plus erythromycin for 5 days, and it reduced respiratory distress and necrotizing enterocolitis compared with placebo. The regimen is the prescriber's; the nursing point is that the course is part of the expectant-management plan, not an optional extra.
  • Intracervical catheters should be avoided after rupture of membranes, because they "have been shown to nearly double the risk of intraamniotic infection compared with pharmacologic induction methods." A mechanical ripening method that would be routine with intact membranes becomes a specific harm once the barrier is gone.
  • Transfer is a treatment. Tocolysis "is important to allow for additional time to be transferred to a tertiary care center," and the named team includes obstetric sonographers for cervical length and fetal metrics, maternal-fetal medicine for complex cases, and neonatologists: "Neonatologists are also frequently engaged early when PTB is anticipated," so they can "prepare the neonatal intensive care unit" before the birth. A baby delivered at a hospital that can care for it has already received part of the benefit.
  • Cerclage — "three well-accepted indications." History-indicated (prophylactic), for a qualifying history of cervical insufficiency, placed at 12 to 14 weeks; ultrasound-indicated, for a prior spontaneous loss or preterm birth before 34 weeks with cervical length under 25 mm before 24 weeks; and a third, exam-indicated (rescue or emergency), when a physical exam finds cervical change such as dilation of 1 cm or more or prolapsed membranes on speculum exam, placed before 24 weeks. No cerclage is placed with active preterm labor, ruptured membranes, placental abruption, intrauterine infection, fetal demise or a lethal fetal anomaly, and initial dilation beyond 4 cm carries a poor prognosis. In published cerclage series the stitch is generally removed at 36 to 37 weeks, or earlier if labor, ruptured membranes or infection intervene.
  • Progesterone — one drug is gone and the other has a hard qualifier. Intramuscular 17-alpha hydroxyprogesterone caproate is not an option at all. The FDA announced on 6 April 2023: "Effective today, Makena and its generics are no longer approved and cannot lawfully be distributed in interstate commerce," after the confirmatory study "did not verify clinical benefit." The preterm-labor source agrees: "Intramuscular progesterone therapy is no longer recommended for the prevention of PTB." It is withdrawn, not narrowed. Vaginal progesterone survives, with a condition: "vaginal progesterone supplementation does not reduce the risk of recurrent sPTB unless the patient also has a shortened cervical length," and "Vaginal progesterone supplementation is not recommended in asymptomatic individuals." The short-cervix qualifier is not a preference; it is the boundary of the evidence.

Nursing considerations

The RN-specific layer — each action paired with the reason it matters.

Assessment & monitoring
Swab for fetal fibronectin before anyone performs a digital examination, and before any exposure to blood or lubricant.
Why: The test must be obtained before any digital cervical exam, before blood exposure and away from recent intercourse, each of which "can all lead to false-positive results." Its value is entirely in its negative predictive value, so a contaminated false positive destroys the one thing it was going to tell the team.
Chart maternal temperature on a schedule during expectant management, not when someone feels unwell.
Why: Chorioamnionitis "presents as a febrile illness," so temperature is the surveillance instrument for the infection clock that started when the membranes ruptured.
Read fetal tachycardia (above 160 beats/min) as an infection sign, and assess fever, uterine tenderness and discharge alongside it rather than treating it as a tracing problem.
Why: It is named explicitly in the intraamniotic infection assessment set, together with maternal fever, uterine tenderness and purulent or foul-smelling discharge. Interpreting it only as fetal tachycardia loses the diagnosis that changes the plan.
Read a white cell count only alongside clinical signs — on its own it is nonspecific — and expect a rise after a steroid dose.
Why: Quoted: the count is "nonspecific" absent clinical findings. Antenatal corticosteroids raise it independently, so acting on the number alone generates false alarms and unnecessary deliveries.
Know the four findings that end expectant management and check for them every shift: nonreassuring fetal status, intraamniotic infection, placental abruption, prolapsed umbilical cord.
Why: Expectant management before 34 weeks is the recommended default, so the discipline of the admission is knowing exactly what cancels it. And tocolytics themselves carry a higher risk of intrauterine infection before 34 weeks.
Follow amniotic fluid volume on serial ultrasound, not only the temperature chart.
Why: Prolonged oligohydramnios has two specific consequences — pulmonary hypoplasia and limb contractures with skeletal deformities — and both accumulate with time rather than announcing themselves. Fluid volume is the measurement that tracks them.
Interventions & safety
Minimize digital vaginal examinations after rupture of membranes, and perform one only if delivery appears imminent or the patient is in active labor.
Why: Digital exams "increase the risk of intraamniotic infection in patients with ROM." "Multiple vaginal exams post rupture of membranes" are independently listed as a chorioamnionitis risk factor — this is iatrogenic harm the team controls entirely.
Hang the group B streptococcus prophylaxis the moment preterm labor is diagnosed, not after the cervical examination or the admission paperwork.
Why: Penicillin "administered 4 or more hours before delivery" is what "provides highly effective protection against early-onset GBS disease." A preterm patient has not reached the 36 to 37 6/7-week screening window, so unknown status plus prematurity is itself the indication. The clock is the intervention.
Question magnesium running with nifedipine unless the magnesium is explicitly for neuroprotection, and say which indication is running at every handoff.
Why: Magnesium is "not advised… in conjunction with calcium channel blockers, unless for neuroprotection, due to the risk of maternal respiratory depression." The same drug also has three obstetric indications — seizure prophylaxis, neuroprotection, and an unsupported tocolytic role — so naming the indication prevents both the interaction and the wrong-reason error.
Check the drug-specific cautions before each tocolytic dose: gestational age before indomethacin (not after 32 weeks), blood pressure and cardiac history before nifedipine, and any calcium channel blocker before magnesium.
Why: Some of these change during an admission rather than being fixed on arrival — the gestational-age line is crossed, the pressure falls — and new fever or a changing tracing goes straight to the provider.
Stop the tocolytic at 48 hours. Do not set up a maintenance infusion and do not give a second course.
Why: Evidence does not suggest that any class is "sufficient for maintenance tocolysis," and "repeat tocolytic therapy is not recommended." Continuing exposes the patient to the drug's adverse effects with no demonstrated benefit, and indomethacin in particular becomes a fetal hazard past 32 weeks.
Monitor the adverse effect each tocolytic actually causes: maternal hypotension with nifedipine, and gastrointestinal effects with indomethacin alongside the fetal ductal and fluid concerns.
Why: The sourced nursing role includes "monitoring maternal and fetal vital signs" and "administering critical medications such as tocolytics and corticosteroids." Nifedipine's documented maternal effects are flushing, headache, dizziness, nausea and hypotension with no fetal risks shown, so blood pressure is the parameter around each dose.
Patient teaching
Teach the warning-sign list by name: contractions every 10 minutes or more often, leaking fluid or bleeding, pelvic pressure, a low dull backache, menstrual-like cramps, and abdominal cramps with or without diarrhea. Say to contact the provider for any of them.
Why: This is the sourced patient-facing list, and four of its six items are things patients routinely dismiss as normal pregnancy discomfort. A patient told only to watch for contractions will stay home with the backache and the pressure.
Say "report fluid leakage, ever" without qualification — no amount, no colour, no duration threshold.
Why: Quoted teaching: patients should present for evaluation "if they ever experience leakage of fluid during pregnancy," because rupture must be ruled out given "the increasing risk of complications associated with a delayed diagnosis." Adding a threshold invites the patient to wait past it.
Explain what each medicine is for, in plain terms: the steroid is for the baby's lungs, gut and brain; the magnesium is for the baby's brain, not to stop the labor; the tocolytic is buying 48 hours; the antibiotic protects the newborn from group B strep.
Why: It is honest and it is also practical. A patient who believes magnesium is stopping her labor reads its continuation as success and its cessation as failure, and a patient told her labor is being stopped experiences the eventual delivery as a treatment failure rather than as the anticipated outcome.
For a prior preterm birth, be precise about progesterone: the intramuscular form is withdrawn from the market and recommended against, and vaginal progesterone is only offered if the cervix is short.
Why: The FDA withdrew intramuscular 17-OHPC and its generics in April 2023 ("Makena and its generics are no longer approved"), and "Intramuscular progesterone therapy is no longer recommended for the prevention of PTB." Vaginal progesterone "does not reduce the risk of recurrent sPTB unless the patient also has a shortened cervical length." Patients who had the injection in a previous pregnancy will ask for it again, and the answer is that it no longer exists, not that it was reserved for someone else.
Work the two modifiable levers deliberately: smoking cessation and avoidance of recreational drugs.
Why: Substance use is on the preterm labor risk list, and cigarette smoking and recreational drug use are on the rupture-of-membranes list. Most of the rest of the risk on this page is historical or structural, which makes the short modifiable list worth real time rather than a line on a discharge sheet.
Prepare her for transfer and for the neonatal team before either happens.
Why: Transfer to a tertiary centre is a named management step, and "Neonatologists are also frequently engaged early when PTB is anticipated," and they can give parents prognostic information before the birth. A transfer explained in advance is a plan; a transfer announced at 3 a.m. is an emergency, and the difference is entirely in the preparation.

How a real nurse thinks

The clinical-judgment loop, worked for a typical presentation — reasoning, not reference.

  1. 1
    Recognize cues

    Three clusters and one absence. The diagnostic cluster: regular contractions every 6 minutes plus a cervix at 2 cm — short of the 3 cm list item, but "treatment also benefits patients who are at high risk of preterm delivery, even if they have not yet reached 3 cm dilation," and her cervical length puts her there — at 29 3/7 weeks, before 37. The risk cluster: a prior preterm birth at 33 weeks, which is the anchor risk factor on the list, and a cervical length of 18 mm, inside the "less than 15 mm to 20 mm" short-cervix band and below the 25 mm cerclage threshold. The reassuring cluster, which is real: temperature 37.1 °C, no pooling on speculum, membranes intact, and a Category I tracing with moderate variability and no decelerations. The absence that matters: she has no GBS result, because at 29 weeks nobody could have taken one. The positive fibronectin is worth noting precisely, because it is the cue most likely to be over-read.

  2. 2
    Analyze cues

    This is preterm labor: contractions plus cervical change. The fibronectin adds very little for this patient specifically, and the reason is her cervix: at 18 mm she falls in the band that is high risk regardless of the fibronectin result, so the positive result changes nothing she was not already. It would have mattered at an intermediate length — a positive fibronectin with a cervix between roughly 20 and 30 mm is itself a rule-in for birth within 7 days. What genuinely raises concern is the 18 mm cervix with a prior preterm birth, a combination that predicts delivery rather than merely flagging risk. Now sort the gestational age against the protocol. At 29 3/7 weeks she is in the 24 to 33 6/7-week core management block, which means corticosteroids are standard, tocolysis is a 48-hour course, magnesium neuroprotection is recommended, and GBS prophylaxis is universal. Because she is under 32 weeks, magnesium is indicated for neuroprotection and indomethacin rather than nifedipine is the tocolytic — the crossover exists because the ductus arteriosus becomes prostaglandin-sensitive after 32 weeks. Check the drug-specific cautions: under 32 weeks, indomethacin is not yet contraindicated, and whether tocolysis is used at all is decided by the provider. And unknown GBS status with preterm labor is itself the indication for prophylaxis, so nothing is waiting on a culture.

  3. 3
    Prioritize

    The ordering principle is which action has a clock attached. First, hang the penicillin G, because it is given 4 or more hours before delivery to protect the newborn and she could deliver inside that window. Second, give the first corticosteroid dose, because the steroid needs time and it is the intervention that helps fetal lung maturity. Third, start magnesium for neuroprotection, which needs to be running within 24 hours of an early preterm birth. Fourth, start the tocolytic, which is the least important of the four because its only job is to hold the door open for the other three. Fifth, call for transfer, because this hospital has no neonatal intensive care unit and geography is part of the treatment. Continuous monitoring runs throughout.

  4. 4
    Generate solutions

    Anticipate penicillin G 5 million units intravenously as a loading dose, then 2.5 to 3 million units every 4 hours until delivery, for unknown GBS status in preterm labor. If she reports a penicillin allergy, anticipate an allergy-history assessment rather than a reflex substitute; the allergy regimen is the prescriber's. Anticipate antenatal corticosteroids as ordered, for fetal lung maturity. Anticipate magnesium sulfate for fetal neuroprotection, with the reason given to her as brain protection rather than labor-stopping. Anticipate indomethacin for no more than 48 hours, and be ready to say why nifedipine is not the choice at this gestational age. Anticipate transfer to a centre with a neonatal intensive care unit, with the neonatal, anesthesia and high-risk obstetric teams notified in advance. And anticipate that if nifedipine is proposed later, the magnesium-plus-nifedipine combination must be questioned because of maternal respiratory depression risk.

  5. 5
    Take action

    Hang the penicillin first and document the time, because the 4-hour interval is what determines whether it counted. Give the betamethasone and write the time of the second dose on the board. Start the magnesium and tell her, in one sentence, that it is there to protect the baby's brain and is not being given to stop her labor. Start the indomethacin with the 48-hour stop time written into the order, not left to memory. Make the transfer call and tell her what the receiving hospital is and why she is going. Keep continuous monitoring running. Check her temperature on the schedule rather than on request. Do not perform further digital examinations beyond the one that established cervical change. And set her expectations honestly: the medicines are buying about two days, and those two days are what change how her baby does — she is not being told her labor will be stopped.

  6. 6
    Evaluate

    Evaluate against what the treatment actually promises. Success is not a stopped labor. Success is the second betamethasone dose given, magnesium running before delivery, four hours of penicillin in her before the baby arrives, and delivery happening at a hospital with a neonatal intensive care unit. Watch for the findings that would change the plan: a rising temperature or fetal tachycardia, which would mean intraamniotic infection; bleeding, which would raise abruption; and loss of variability or late decelerations, which would make nonreassuring fetal status a reason to deliver — each goes to the provider at once. Stop the tocolytic at 48 hours regardless of whether contractions persist, because maintenance is unsupported and repeat courses are not recommended. If she reaches 32 weeks still undelivered, the indomethacin is no longer an option at all. Postpartum, her prior-preterm-birth history is now two births, and the counselling for a future pregnancy turns on cervical length surveillance. If she asks about "the progesterone shot" she may have heard of, the answer is that intramuscular 17-OHPC was withdrawn by the FDA in April 2023 and is recommended against; vaginal progesterone is considered only if a short cervix is actually found, because without one it does not reduce the risk of recurrence.

Scenario — you’re the nurse

Work each question before revealing the answer. Rationales explain the wrong options too.

Labor and delivery triage at a community hospital without a neonatal intensive care unit

A 26-year-old, gravida 2 para 1, at 29 3/7 weeks. Her first child was born at 33 weeks. She has had contractions every 6 minutes for three hours and a low, dull backache since this morning.

Speculum — no pooling; membranes intact
Fetal fibronectin — swabbed before any digital exam; positive, 50 ng/mL or above
Transvaginal cervical length — 18 mm; cervix 2 cm dilated on the subsequent examination
Vitals and tracing — temperature 37.1 °C · fetal baseline 145 with moderate variability, no decelerations
GBS status — unknown; she has not reached the 36 to 37 6/7-week screening window
Q1 Multiple choice
A patient at 30 weeks is started on magnesium sulfate. She asks what it is for. The best response is:
  1. A. "It is the most effective medicine we have for stopping preterm labor."
  2. B. "It protects your baby's brain, reducing the risk of cerebral palsy and bleeding in the brain. It is not being given to stop your labor."
  3. C. "It matures your baby's lungs before delivery."
  4. D. "It prevents infection now that you are in preterm labor."
Reveal answer & rationale
Answer: B
Magnesium "provides neuroprotection for the neonate" when given within 24 hours of an early preterm birth, reducing cerebral palsy risk and severe intraventricular hemorrhage; the WHO threshold is before 32 weeks (B). Option A is the killed claim: studies "have failed to demonstrate its effectiveness in pregnancy prolongation," and the source states that it "is used for neuroprotection." Option C describes the corticosteroid, and option D describes the group B streptococcus prophylaxis. Learning which of the three simultaneous infusions does what is the point — the same magnesium also runs on the preeclampsia page for a completely different reason, seizure prophylaxis.
Q2 Select all that apply
A patient at 33 weeks in preterm labor is prescribed a tocolytic. Which statements are correct? Select all that apply.
  1. A. Nifedipine is preferred at this gestational age and maternal hypotension is the expected adverse effect
  2. B. Indomethacin is contraindicated after 32 weeks because of premature ductus arteriosus closure
  3. C. The goal is to prolong gestation by two to seven days, particularly to allow corticosteroids to work
  4. D. A maintenance infusion should follow the initial 48 hours to prevent recurrence
  5. E. Magnesium sulfate running with nifedipine should be questioned unless the magnesium is for neuroprotection
Reveal answer & rationale
Answer: A, B, C, E
Nifedipine "is often used for tocolysis, especially after 30 to 32 weeks of EGA," and its documented maternal effects include hypotension (A). Indomethacin is "contraindicated after 32 weeks of gestational age" for ductal closure, with oligohydramnios, gastric perforation and pulmonary hypertension also listed (B). The purpose is "to prolong gestation for two to seven days," with the demonstrated benefit being the 48-hour steroid window (C). And magnesium is "not advised… in conjunction with calcium channel blockers, unless for neuroprotection, due to the risk of maternal respiratory depression" (E). Option D is the error: no class has been shown "sufficient for maintenance tocolysis," and "repeat tocolytic therapy is not recommended."
Q3 Put in order
A patient at 28 weeks arrives in preterm labor. Her group B streptococcus status is unknown. Put the nurse's actions in priority order:
  1. A. Give the first dose of betamethasone
  2. B. Hang penicillin G 5 million units intravenously
  3. C. Arrange transfer to a facility with a neonatal intensive care unit
  4. D. Start the tocolytic
Reveal answer & rationale
Correct order: B → A → D → C
The ordering principle is which action has the tightest clock. Prophylaxis first (B): penicillin "administered 4 or more hours before delivery" is what "provides highly effective protection against early-onset GBS disease," and unknown status with preterm labor before 37 weeks is itself the indication, so nothing waits on a culture she could not have had at 28 weeks. Betamethasone second (A): it needs time to act, and it is the intervention that helps fetal lung maturity. The tocolytic third (D): its only job is to hold the door open for the other measures. Transfer last in sequence but not in importance (C) — it is a named management step, and it is arranged while the drugs are running rather than before them.
Q4 Multiple choice
A patient with preterm prelabor rupture of membranes at 30 weeks is managed expectantly. Which finding requires the nurse to escalate immediately?
  1. A. White blood cell count risen from 11,000 to 15,000 after a betamethasone dose
  2. B. Fetal heart rate baseline 168 bpm sustained over 15 minutes with uterine tenderness
  3. C. Nitrazine paper turning blue on a repeat check
  4. D. Amniotic fluid index slightly lower than the previous week
Reveal answer & rationale
Answer: B
Fetal tachycardia is named in the intraamniotic infection sign set alongside fever, uterine tenderness and foul-smelling discharge — and intraamniotic infection is one of the four contraindications that end expectant management immediately (B). Option A is the trap: an elevated white count is "nonspecific" absent clinical findings, and antenatal corticosteroids raise it independently. Option C adds nothing, since rupture is already diagnosed and "false-positive pH tests are common" in any case. Option D warrants continued surveillance for pulmonary hypoplasia and limb contractures, but it is a trend to follow rather than a reason to deliver tonight. The other three findings that end the wait: nonreassuring fetal status, placental abruption, prolapsed umbilical cord.
Q5 Multiple choice
Which statement by a nursing student about preterm labor management requires correction?
  1. A. "Tocolytics are given to buy about 48 hours so the steroids can work."
  2. B. "The fetal fibronectin swab has to be collected before any digital exam."
  3. C. "The progesterone injection is the standard prevention for anyone with a prior preterm birth."
  4. D. "Digital exams after rupture of membranes increase the risk of intraamniotic infection."
Reveal answer & rationale
Answer: C
Two things are wrong with it (C). Intramuscular 17-OHPC — the injection — was withdrawn by the FDA on 6 April 2023 for lack of evidence of benefit, and "Intramuscular progesterone therapy is no longer recommended for the prevention of PTB." And the surviving option carries a hard qualifier: vaginal progesterone "does not reduce the risk of recurrent sPTB unless the patient also has a shortened cervical length," and it "is not recommended in asymptomatic individuals." The other three are accurate. Tocolysis is "intended to prolong gestation for two to seven days," with the demonstrated benefit being the 48-hour corticosteroid window (A). Fibronectin must be obtained before any digital cervical exam, before blood exposure and away from recent intercourse, since each "can all lead to false-positive results" (B). And digital exams after rupture "increase the risk of intraamniotic infection" and "should be avoided unless delivery appears imminent," with multiple post-rupture exams independently listed as a chorioamnionitis risk factor (D).

Common questions

What causes preterm labor?
Common causes and risk factors include prior preterm birth — the anchor risk factor. it is the entry criterion for both the ultrasound-indicated cerclage decision and the progesterone decision, so it changes management rather than only estimating risk, shortened cervical length. normal is 35 to 48 mm and risk is under 5% at 30 mm or more; under 15 to 20 mm is high risk regardless of fibronectin, and an intermediate length with a positive fibronectin is high risk too. under 25 mm before 24 weeks with a qualifying history is a cerclage threshold, intrauterine infection — pathway 1, the commonest driver, and the finding that converts expectant management into delivery, uterine overdistention — pathway 3, placental complications — decidual hemorrhage is pathway 2, and others.
What are the early signs of preterm labor?
Early findings include Contractions every 10 minutes or more often, Low, dull backache, or cramps that feel like menstrual cramps, Feeling of pressure in the pelvis, Abdominal cramps with or without diarrhea, A rise in maternal temperature during expectant management, even without other signs.
Which findings should a nurse report immediately in preterm labor?
Report immediately: Leaking fluid from the vagina — at any point in pregnancy, Vaginal bleeding with contractions, Regular contractions with documented cervical change, Cervical change without contractions (possible cervical insufficiency), Maternal fever with fetal tachycardia, uterine tenderness, or purulent or foul-smelling discharge, and others. These signal deterioration that needs rapid intervention.
If tocolytics do not stop preterm labor, why give them at all?
Because the 48 hours they buy are worth more than stopping the labor would be if it were possible. The sourced aim is to "prolong gestation for two to seven days," and the demonstrated benefit is that delaying delivery "by up to 48 hours" allows "for antenatal corticosteroids to help fetal lung maturity in premature neonates" — while the source itself notes that "There have been publications that have questioned if tocolytics have benefits on major neonatal morbidity." In that window four things happen that genuinely change outcomes: the corticosteroid course completes, helping fetal lung maturity; magnesium goes in for fetal neuroprotection if the patient is under 32 weeks; group B streptococcus prophylaxis reaches the four hours it needs; and the patient is transferred to a hospital with a neonatal intensive care unit. Which is also why the rules are what they are: 48 hours maximum, no maintenance infusion, and no repeat course — the window has closed and further exposure has no demonstrated benefit.
Why is indomethacin used below 32 weeks and nifedipine above it?
The line is the ductus arteriosus. Indomethacin is a COX inhibitor, and "COX inhibitors prevent the conversion of arachidonic acid to prostaglandins, which stimulate contractions," which is elegant on a page where prostaglandins are the final common pathway. But the ductus arteriosus is held open by prostaglandins and becomes increasingly sensitive to their withdrawal as gestation advances, so indomethacin is "contraindicated after 32 weeks of gestational age," with oligohydramnios, gastric perforation and pulmonary hypertension as further fetal effects. Nifedipine acts somewhere else entirely — calcium channel blockers "work on T-type calcium channels by inhibiting the entry of calcium into the uterine smooth muscle" — so it has no ductal effect, and "Studies have shown no fetal risks with nifedipine use for the management of preterm labor." It takes over from 32 weeks, where it also "has a better safety profile than other tocolytic medications." Its own cost is maternal: flushing, headache, dizziness, nausea and hypotension, which is the parameter to monitor.
A patient at 31 weeks has unknown group B streptococcus status. Does she wait for a culture?
No, and the reason is a calendar collision worth understanding. Routine screening is a culture between 36 0/7 and 37 6/7 weeks. A patient at 31 weeks has not reached that window, so there is no result to wait for and no way to generate one in time. That is why, when status is unknown, preterm delivery before 37 weeks is an indication for prophylaxis in its own right. Give penicillin G 5 million units intravenously, then 2.5 to 3 million units every 4 hours until delivery, and hang it immediately, because prophylaxis "administered 4 or more hours before delivery" is what "provides highly effective protection against early-onset GBS disease."

Sources

Reviewed by Hae Suk Lee, RN

Educational summary for nursing students. Scenarios are fictional teaching cases. Always verify against current guidelines and your institution's protocols before acting in practice. Not medical advice.

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