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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Preterm = <37 weeks. Extreme preterm <28 weeks. Very preterm 28–31+6 weeks
- Preterm prelabour rupture of membranes (PPROM): membrane rupture <37 weeks before onset of labour
- Antenatal corticosteroids: betamethasone 12 mg IM x2 doses, 24 h apart, if <34 weeks — promote fetal lung maturity
- Tocolysis: nifedipine first-line (NICE NG25) — delays delivery for 48 h to allow steroids to work
- MgSO₄ for neuroprotection: give if delivering <30 weeks — reduces risk of cerebral palsy
- PPROM: erythromycin 250 mg QDS for 10 days. Do NOT give co-amoxiclav (risk of neonatal NEC)
Overview
Preterm birth is defined as delivery before 37 completed weeks of gestation. It is the single most important cause of neonatal morbidity and mortality in the developed world. Preterm labour may occur spontaneously (with or without preceding membrane rupture) or be medically indicated (iatrogenic — for maternal or fetal indications). PPROM is defined as rupture of membranes before 37 weeks in the absence of labour. Management aims to prolong pregnancy long enough for corticosteroids to take effect while minimising risks of infection and fetal compromise.
Epidemiology
Preterm birth occurs in approximately 7–8% of pregnancies in the UK. Approximately 30% of preterm births are medically indicated, 25–30% follow PPROM, and 40–45% are spontaneous preterm labour. Risk factors include previous preterm birth (most important), cervical insufficiency, multiple pregnancy, uterine anomalies, polyhydramnios, infections (BV, UTI, chorioamnionitis), PPROM, and social factors (smoking, low BMI, stress). Cervical length assessment and fetal fibronectin testing can help risk-stratify women with symptoms.
Clinical Features
Symptoms
Regular, painful uterine contractions before 37 weeks
Sensation of pelvic pressure or low back pain
Vaginal watery discharge or gush of fluid (PPROM — "my waters have broken")
Vaginal bleeding or mucoid "show"
Fever, malaise, offensive discharge (suggesting chorioamnionitis)
Reduced fetal movements
Signs
Palpable regular uterine contractions (≥4 per 20 minutes)
Cervical dilatation and/or effacement on speculum or digital examination
Pooling of liquor in the posterior vaginal fornix (PPROM)
Positive fetal fibronectin test (>50 ng/mL) or short cervical length (<15 mm on TVUSS)
Pyrexia, uterine tenderness, maternal or fetal tachycardia (chorioamnionitis)
Investigations
First-line
Speculum examinationVisualise cervix — pooling of liquor (PPROM), cervical dilatation, exclude cord prolapse. Avoid digital VE until labour confirmed
Fetal fibronectin (fFN)Vaginal swab. Useful between 22–34 weeks. Negative result (<50 ng/mL) has excellent NPV (>95%) for delivery within 7 days
Transvaginal cervical lengthCervical length ≥15 mm makes preterm delivery within 7 days unlikely. <15 mm = high risk
CTGAssess fetal wellbeing — continuous monitoring if in established preterm labour
Second-line
FBC, CRPRaised WCC and CRP suggest infection/chorioamnionitis
MSUExclude UTI as a precipitant
HVSSwab for Group B Streptococcus, bacterial vaginosis
IGFBP-1 or PAMG-1Point-of-care tests for PPROM if clinical diagnosis uncertain
Specialist
AmniocentesisRarely performed — culture if chorioamnionitis suspected and diagnosis unclear
1
Antenatal corticosteroids
- Betamethasone 12 mg IM x2 doses, 24 hours apart
- Offer from 24+0 to 33+6 weeks if preterm birth anticipated within 7 days
- Promotes fetal lung maturity — reduces neonatal RDS, IVH, and mortality
- Consider from 23 weeks in discussion with neonatal team
2
Tocolysis (preterm labour)
- Nifedipine (oral) is first-line tocolytic (NICE NG25)
- Purpose: delay delivery by 48 hours to allow corticosteroids to take effect and enable in-utero transfer
- NOT recommended beyond 34 weeks or if chorioamnionitis suspected
- Alternative: atosiban (oxytocin receptor antagonist) IV if nifedipine contraindicated
3
MgSO₄ for neuroprotection
- Give IV MgSO₄ if delivery expected within 24 hours AND <30 weeks gestation
- Loading dose: 4 g IV over 15–20 min. Maintenance: 1 g/h until delivery (max 24 h)
- Reduces risk of cerebral palsy by ~30%
4
PPROM management
- Erythromycin 250 mg QDS orally for 10 days (or until delivery if sooner)
- DO NOT give co-amoxiclav — associated with increased risk of neonatal NEC
- Antenatal corticosteroids as above
- Monitor for signs of chorioamnionitis: maternal pyrexia, tachycardia, uterine tenderness, offensive liquor
- If no signs of infection: conservative management until 37 weeks, then induce
- If chorioamnionitis: deliver immediately regardless of gestation
Complications
- Neonatal RDS: From surfactant deficiency — major cause of preterm morbidity. Reduced by antenatal steroids
- Intraventricular haemorrhage: Risk inversely related to gestation
- Necrotising enterocolitis: Ischaemic bowel necrosis — higher risk with co-amoxiclav in PPROM
- Chorioamnionitis: Ascending infection through ruptured membranes — fever, tachycardia, offensive liquor. Deliver immediately
- Cord prolapse: Risk with PPROM, especially with malpresentation
- Long-term: Cerebral palsy, chronic lung disease, neurodevelopmental delay
UKMLA Exam Tips
- 1Nifedipine = first-line tocolytic (NICE NG25). Purpose is to delay delivery by 48 h for steroids
- 2Betamethasone 12 mg IM x2 (24 h apart) — given from 24 to 33+6 weeks if preterm birth expected
- 3MgSO₄ neuroprotection if <30 weeks — reduces cerebral palsy by ~30%
- 4PPROM: erythromycin 250 mg QDS for 10 days. NEVER co-amoxiclav (NEC risk)
- 5Negative fetal fibronectin (<50 ng/mL) = >95% chance of NOT delivering in 7 days — useful rule-out test
- 6Chorioamnionitis = deliver immediately regardless of gestation. Signs: pyrexia, tachycardia, uterine tenderness
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