Preterm Labour

Onset of regular uterine contractions with cervical change before 37 completed weeks gestation.

Risk factors include previous preterm birth (the strongest predictor), multiple pregnancy, uterine or cervical anomaly, cervical insufficiency, infection (chorioamnionitis, bacterial vaginosis, UTI), polyhydramnios, and antepartum hemorrhage.

Regular, painful uterine contractions accompanied by cervical dilation and effacement, sometimes with a show or ruptured membranes.

Distinguishing true preterm labor from Braxton Hicks contractions or non-specific pelvic pressure is the central diagnostic challenge.

• Clinical assessment of contraction frequency and cervical examination (dilation, effacement)
• Transvaginal ultrasound cervical length: a length under 15 mm supports a high risk of imminent delivery; a length over 15 mm makes preterm birth within 7 days unlikely
• Fetal fibronectin (a biomarker present in cervicovaginal fluid), a negative result has a high negative predictive value for delivery within 7 to 14 days and can avoid unnecessary intervention; used particularly when cervical length is equivocal (15 to 30 mm)
• Exclude and treat infection: MSU, high vaginal swab, and, where membranes are ruptured, assessment for chorioamnionitis (see PPROM entry)

• Tocolysis to delay delivery by 48 hours, allowing time for corticosteroids and, where relevant, in-utero transfer to a unit with appropriate neonatal facilities: nifedipine 20 mg PO loading dose, then 10 to 20 mg PO every 6 to 8 hours (maximum 24 hour dose per local protocol, commonly up to 60 to 160 mg/day), or atosiban (oxytocin receptor antagonist) by IV infusion where available; tocolysis is generally not continued beyond 48 hours and is avoided where there are contraindications (chorioamnionitis, severe pre-eclampsia, abruption, or non-reassuring fetal status)
• Corticosteroids for fetal lung maturation: betamethasone 12 mg IM, 2 doses 24 hours apart, given for anticipated preterm delivery between roughly 24 and 34+6 weeks (up to 35+6 in some protocols); a single rescue course may be considered if delivery remains imminent more than 1 to 2 weeks after an initial course, per specialist guidance
• Magnesium sulfate for fetal neuroprotection: given before anticipated delivery under 30 to 32 weeks (threshold varies by protocol), typically 4 g IV loading dose over 15 to 30 minutes, then 1 g/hour maintenance, reduces the risk of cerebral palsy in survivors
• Group B streptococcus prophylaxis if status unknown or previously positive: benzylpenicillin 3 g IV loading dose, then 1.5 g IV every 4 hours until delivery (alternatives per allergy status: cefazolin, clindamycin, or vancomycin depending on allergy severity and local resistance)
• Antibiotics are not given routinely for preterm labor with intact membranes in the absence of confirmed infection, given lack of proven benefit and some evidence of harm in this specific context
• Mode and timing of delivery individualized by gestation, presentation, and fetal status

Referral: obstetric-led care with neonatal team involvement; in-utero transfer to a tertiary unit with appropriate NICU facilities if delivery under roughly 27 to 28 weeks is anticipated and local facilities are insufficient.