Preterm Labour and Birth

not tied to a single RCOG Green-top. RCOG's preterm-birth guidance is split across several specific Green-tops (antenatal corticosteroids: GTG 74; preterm prelabour rupture of membranes: GTG 73; cervical cerclage: GTG 75) — see those files for guideline-specific detail this overview doesn't duplicate.

Definitions

• Preterm birth: delivery before 37+0 weeks gestation
• Very preterm: before 32 weeks
• Extremely preterm: before 28 weeks
• Late preterm: 34-36+6 weeks
• Preterm birth affects approximately 7-8% of pregnancies in the UK
• Leading cause of neonatal mortality and morbidity

Risk Factors

• Previous preterm birth (strongest predictor — recurrence risk 15-50%)
• Previous cervical surgery (LLETZ, cone biopsy)
• Short cervical length (<25mm on TVUS at 16-24 weeks)
• Multiple pregnancy
• Uterine anomalies (septate, bicornuate)
• Polyhydramnios
• Cervical insufficiency
• Infection (bacterial vaginosis, UTI, chorioamnionitis)
• PPROM (preterm prelabour rupture of membranes)
• Placental abruption
• Smoking, substance misuse
• Low BMI
• Short inter-pregnancy interval (<6 months)

Prediction and Prevention

Cervical Length

• TVUS cervical length measurement at 16-24 weeks in high-risk women
• Short cervix (<25mm): consider cervical cerclage or vaginal progesterone
• Cervical cerclage: consider if cervical length <25mm before 24 weeks with previous preterm birth

Vaginal Progesterone

• 200mg pessary daily from 16 weeks to 34 weeks
• Indicated for: short cervix (<25mm), previous spontaneous preterm birth
• Reduces preterm birth by approximately 40% in selected women

Fetal Fibronectin (fFN)

• Cervicovaginal swab in symptomatic women (24-34 weeks)
• Negative fFN (<50 ng/ml): high negative predictive value (>95% will NOT deliver within 7 days)
• Useful for avoiding unnecessary admission and treatment
• Not valid if: sexual intercourse in preceding 24 hours, vaginal examination, speculum examination, vaginal bleeding

Management of Preterm Labour

Tocolysis

• Nifedipine (oral): first-line tocolytic
  • Loading: 20mg, then 10-20mg 3-4 times daily for 48 hours
  • Side effects: flushing, headache, hypotension
• Atosiban (IV oxytocin receptor antagonist): second-line
  • Fewer side effects than nifedipine
  • Used if nifedipine contraindicated or not tolerated
• Purpose: delay delivery for 48 hours to allow corticosteroids and in-utero transfer
• Tocolysis is NOT recommended beyond 48 hours or after 34 weeks

Antenatal Corticosteroids

• Betamethasone 12mg IM — two doses 24 hours apart (or dexamethasone 6mg IM — four doses 12 hours apart)
• Indicated: 24+0 to 33+6 weeks when preterm delivery is anticipated within 7 days
• Reduces: RDS (respiratory distress syndrome), IVH (intraventricular haemorrhage), NEC (necrotising enterocolitis), neonatal death
• Optimal benefit: 24 hours to 7 days after second dose
• Rescue course: may be considered if >7 days since first course and delivery imminent (not routinely repeated)

Magnesium Sulphate for Neuroprotection

• 4g IV loading dose over 15-20 minutes, followed by 1g/hour infusion for up to 24 hours
• Indicated: <30 weeks gestation when preterm delivery is expected within 24 hours
• Reduces risk of cerebral palsy by approximately 30%
• Same monitoring as for eclampsia (reflexes, respiratory rate, urine output)

In-Utero Transfer

• Transfer to a unit with appropriate neonatal care level if preterm delivery anticipated
• <27 weeks: transfer to a level 3 NICU
• 27-32 weeks: level 2 or 3 unit

Mode of Delivery

• Vaginal delivery is appropriate for most preterm births
• Caesarean section indications: standard obstetric indications (breech, fetal distress, placenta praevia)
• Very preterm breech: caesarean section often preferred but no strong evidence of benefit
• Avoid instrumental delivery where possible in very preterm infants

Important Facts for MRCOG

• Previous preterm birth is the strongest risk factor
• Nifedipine is first-line tocolytic
• Tocolysis purpose: buy 48 hours for corticosteroids, NOT to prolong pregnancy
• Corticosteroids: effective 24+0 to 33+6 weeks
• Magnesium sulphate for neuroprotection: <30 weeks — reduces cerebral palsy by ~30%
• Negative fetal fibronectin has >95% NPV for not delivering within 7 days
• Cervical cerclage considered if short cervix + previous preterm birth
• Vaginal progesterone reduces preterm birth by ~40% in women with short cervix

Source: NICE NG25 (Preterm labour and birth) — general overview, (2019 (NICE NG25))

Read the original on nice.org.uk

Clinically reviewed by NHS obstetricians and gynaecologists · Source last updated 2019 (NICE NG25)

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