PassFinals
Obstetrics

Preterm Labour and Birth

Preterm labour is suspected or established labour before 37 weeks; management aims to identify true imminent birth, gain safe time for corticosteroids, magnesium neuroprotection and in-utero transfer, and avoid delaying birth when infection, bleeding or fetal compromise makes delivery safer.

In a nutshell

Preterm labour is suspected or established labour before 37 weeks. Confirm cervical change and membrane status, assess infection and fetal compromise, and involve neonatology. Offer corticosteroids at 24+0–33+6 weeks, consider them at 34+0–35+6 weeks, offer magnesium sulfate at 24+0–29+6 weeks when birth is within 24 hours and consider it at 30+0–33+6 weeks. Use nifedipine selectively for time to give steroids or transfer, and do not tocolyse infection, bleeding or fetal compromise.

Classic presentation

At 29 weeks, a person has regular contractions and a dilating cervix with intact membranes. Start corticosteroids, offer magnesium sulfate, consider nifedipine if no contraindication, involve neonatology and arrange appropriate in-utero transfer.

Key points

  • Preterm symptoms do not prove established labour; assess cervical change.
  • At 30 weeks or more with intact membranes, cervical length over 15 mm makes birth within 48 hours unlikely; fetal fibronectin is an alternative if ultrasound is unavailable or unacceptable.
  • Offer steroids 24+0–33+6 weeks; consider 34+0–35+6 weeks; a single repeat course is restricted to very high risk below 34 weeks and no more than 2 courses.
  • Offer magnesium sulfate 24+0–29+6 weeks and consider it 30+0–33+6 weeks when birth is within 24 hours.
  • Use nifedipine only when the benefit of delay outweighs risk; infection, significant bleeding and fetal compromise are contraindications.
  • For PPROM, use erythromycin prophylaxis and do not use co-amoxiclav; established preterm labour also needs NICE NG195 intrapartum antibiotic consideration.

First-line investigation

Clinical assessment and sterile speculum examination; at 30+0 weeks or more with intact membranes use cervical length, or fetal fibronectin if cervical length is unavailable or unacceptable.

Management

Assess labour, membranes and danger

  • Perform maternal and fetal assessment, sterile speculum examination and appropriate cervical-length or fetal-fibronectin testing, while looking for infection, bleeding and fetal compromise.1,4

Prepare the fetus and neonate

  • Offer corticosteroids at 24+0–33+6 weeks, consider them at 34+0–35+6 weeks, and offer or consider magnesium sulfate according to gestation when birth is expected within 24 hours.1,3

Buy safe time only

  • Use nifedipine selectively for steroids or transfer when membranes are intact and no contraindication exists; manage PPROM with erythromycin and combined infection assessment.1,2,3

Deliver in the right place

  • Arrange in-utero transfer and neonatal care, give NICE NG195 intrapartum antibiotics for established preterm labour when indicated, and deliver promptly if infection, bleeding or fetal compromise makes delay unsafe.1,4,5

Exam traps

  • Do not use cervical length and fetal fibronectin together to diagnose preterm labour.
  • Magnesium sulfate is for fetal neuroprotection here, not eclampsia treatment.
  • Do not give more than 2 courses of antenatal corticosteroids.
  • Do not use tocolysis for infection, significant bleeding or fetal compromise.
  • Do not give co-amoxiclav for PPROM prophylaxis.
  • Do not delay urgent birth for steroids, magnesium or transfer.

Illustrations

Cervical-length measurementTransvaginal ultrasound with calipers demonstrating cervical-length measurement and a note that NICE uses 15 mm to assess likelihood of birth within 48 hours in symptomatic people at 30 weeks or more.Mikael Häggström, Wikimedia Commons · CC0

Key sources

  1. NICE NG25, Preterm labour and birth (Current NICE guideline published 20 November 2015 and last updated 10 June 2022: diagnosis, PPROM, tocolysis, corticosteroids, magnesium sulfate and intrapartum care)Updated 10 Jun 2022
  2. RCOG Green-top Guideline No. 73, Care of women presenting with suspected PPROM from 24+0 weeks (Current RCOG PPROM guidance reviewed in October 2024 and extended for 2 years: diagnosis, combined infection assessment, antibiotics and expectant-care principles)
  3. BNF, current obstetric prescribing information (UK prescribing source for corticosteroids, magnesium sulfate, nifedipine and erythromycin; direct access was restricted and unsupported details were deferred to BNF and local protocols)
  4. NICE NG195, Neonatal infection: antibiotics for prevention and treatment (Current NICE guidance last updated 13 May 2026: intrapartum antibiotics for preterm labour, chorioamnionitis and early-onset neonatal infection risk)Updated 13 May 2026
  5. NICE NG255, Suspected sepsis in pregnant or recently pregnant people (Pregnancy-specific sepsis guidance published 19 November 2025 and reviewed 5 March 2026: cultures, high-risk treatment and source control)Updated 5 Mar 2026

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.