Key Facts

Premature rupture of membranes (PROM) refers to rupture of the fetal membranes prior to the onset of labour. When this occurs before 37 weeks, it is termed preterm PROM (PPROM). It is a significant cause of preterm birth and is associated with infectious complications.

Epidemiology

• PROM at term: occurs in approximately 8-10% of pregnancies
• PPROM: complicates 2-3% of pregnancies
• PPROM is responsible for 30-40% of all preterm births
• Most women with PROM at term will labour spontaneously within 24 hours (>60%)

Aetiology

• Infection (chorioamnionitis, bacterial vaginosis, GBS colonisation)
• Previous PPROM (recurrence risk 16-32%)
• Smoking
• Previous cervical surgery (cone biopsy, LLETZ)
• Uterine overdistension (polyhydramnios, multiple pregnancy)
• Cervical insufficiency
• Amniocentesis (1% risk)
• Low socioeconomic status, poor nutrition

Pathophysiology

• Weakening of the chorioamniotic membranes through enzymatic degradation (matrix metalloproteinases)
• Infection causes neutrophil infiltration and release of proteolytic enzymes
• Mechanical stress from uterine contractions or overdistension
• Programmed cell death and collagen remodelling contribute in term PROM

Typical Presentation

• Sudden gush of clear fluid from the vagina
• Continuous trickle or leaking of fluid
• Wet underwear or sanitary pad
• Fluid may be clear, straw-coloured, or blood-tinged

Signs on Examination

• Pooling of liquor in the posterior vaginal fornix on speculum examination
• Reduced liquor volume on ultrasound
• Positive bedside tests (nitrazine test, ferning, IGFBP-1, PAMG-1)

Red Flags

• Maternal pyrexia (>38°C) suggesting chorioamnionitis
• Maternal tachycardia (>100 bpm)
• Uterine tenderness
• Offensive vaginal discharge
• Fetal tachycardia (>160 bpm)
• Raised CRP or WCC
• Cord prolapse (especially with high presenting part)

Bedside

• Sterile speculum examination: look for pooling of liquor in posterior fornix
• IGFBP-1 or PAMG-1 test (Actim PROM / PartoSure): bedside immunoassay with high sensitivity and specificity
• Nitrazine test (pH >6.5 suggests amniotic fluid - less specific)
• Temperature, pulse, blood pressure
• CTG for fetal monitoring

Bloods

• FBC (WCC as baseline)
• CRP (baseline and twice weekly)
• Group and save
• Blood cultures if pyrexial

Imaging

• Ultrasound: assess liquor volume (oligohydramnios supports diagnosis), fetal presentation, growth

Special Tests

• High vaginal swab and low vaginal swab (including GBS culture)
• Urine MC&S
• Avoid digital VE unless in established labour (increases infection risk)

Non-pharmacological

• PROM at term (≥37 weeks): offer induction of labour (NICE NG25 recommends within 24 hours); or expectant management with 4-hourly observations for up to 24 hours if woman prefers
• PPROM (24-36+6 weeks): expectant management with close monitoring
• Regular observations: temperature and pulse 4-hourly, FBC and CRP twice weekly
• Avoid digital VE until in established labour

Pharmacological

• Erythromycin 250mg QDS PO for 10 days (or until labour, whichever sooner) - ORACLE trial evidence
• Do NOT use co-amoxiclav (increased NEC risk - ORACLE trial)
• Antenatal corticosteroids: betamethasone 12mg IM × 2 if 24-34+6 weeks
• Magnesium sulphate: 4g IV if delivery expected within 24 hours at <30 weeks (neuroprotection)
• GBS prophylaxis: IV benzylpenicillin 3g then 1.5g 4-hourly in labour if GBS positive or unknown

Surgical/Interventional

• Induction of labour at 37 weeks if PPROM has been managed expectantly
• Earlier delivery if signs of chorioamnionitis, fetal compromise, or significant abruption
• Mode of delivery guided by fetal presentation and condition

Referral Criteria

• All women with suspected PPROM require hospital assessment
• In utero transfer to tertiary unit if <27 weeks
• Neonatal counselling at extreme prematurity

• PROM at term: >90% will labour within 24 hours; 95% within 72 hours
• PPROM: 50% will deliver within 1 week; latency inversely proportional to gestational age
• Chorioamnionitis rate: 15-25% with PPROM
• Cord prolapse risk: 1-2% (higher with malpresentation)
• Neonatal sepsis: 2-5%
• Pulmonary hypoplasia risk: significant if PPROM <24 weeks with severe oligohydramnios
• Recurrence risk: 16-32%
• Perinatal mortality with PPROM: depends on gestational age and complications

ORACLE Trial Summary

Chorioamnionitis Diagnostic Criteria