Preterm prelabour rupture of membranes

Synonym: preterm premature rupture of membranes

What is premature rupture of membranes?

Premature rupture of membranes (PROM) refers to rupture of the membranes occurring prior to the onset of labour and can occur from 37 weeks of gestation onwards.

Most women go into spontaneous labour within 24 hours of rupturing their membranes but 6% of women will not be in spontaneous labour within 96 hours. However, the earlier in gestation the rupture occurs, the less likely that the onset of labour will be within a specified time period.

Epidemiology

• PROM occurs in 6-19% of term pregnancies.

• The risk of serious neonatal infection at term is 1%, rather than 0.5% for women with intact membranes.¹

• P-PROM occurs in 3% of all pregnancies and is associated with 40% of preterm deliveries.²

• It can lead to significant morbidity and mortality.

Premature rupture of membranes risk factors³

Risk factors for P-PROM are:

• Smoking: heavy cigarette smoking increases the risk of P-PROM. The increased risk is greatest at gestational ages lower than 28 weeks.⁴

• Previous preterm delivery.

• Vaginal bleeding (at any time during the pregnancy).

• There is an association between lower genital tract infection and P-PROM.

• Around a third of women with P-PROM have positive amniotic fluid cultures.

Presentation

The mother may give history of a 'popping sensation' or a 'gush' with continuous watery liquid draining thereafter. Their underwear or pad may be damp.

Investigations

The earliest clinical signs of ascending infection (chorioamnionitis) are fetal tachycardia and a mild increase in maternal temperature. An offensive vaginal discharge may also be present in some women.

• Diagnosis of premature rupture of membranes:⁵

  • Actually seeing amniotic fluid draining from the cervix and pooling in the vagina after the woman has been lying down for 30 minutes is the most accurate test. Sterile speculum examination: check for liquor and for the umbilical cord.

  • Clinicians should consider performing an insulin-like growth factor-binding protein 1 (IGFBP-1) or placental alpha microglobulin-1 (PAMG-1) test of vaginal fluid to guide further management.²

  • Nitrazine testing is no longer recommended, as urine, semen and other contaminants may give a false positive test result.
    

  • Regular pad checks.

• Ultrasound may be useful to check for gestation and liquor volume.

• Temperature monitoring at least 12-hourly for ascending infection:
  

  • High vaginal swab.

  • If infection is suspected, check FBC (for WCC), CRP, MSU and blood cultures; start appropriate antibiotic treatment if tests, along with clinical signs, confirm intrauterine infection.

• Fetal monitoring.

Premature rupture of membranes treatment and management

• Refer urgently to hospital if:
  

  • P-PROM is suspected.

  • Ascending infection is suspected: maternal or fetal tachycardia, temperature, abdominal tenderness.

• Women are usually seen in hospital and admitted for the first 48 hours. After this time, management at home - which includes taking 4- to 8-hourly temperatures - may be possible for some women.

• Antibiotic administration:
  

  • Prophylactic antibiotics for P-PROM appear to reduce complications due to preterm delivery and postnatal infection.⁶

  • In the UK, both the National Institute for Health and Care Excellence (NICE) and the Royal College of Obstetricians and Gynaecologists (RCOG) recommend the use of erythromycin 250 mg qds for 10 days (or until labour is established if this is sooner) following the diagnosis of P-PROM (unlicensed use).^{2 5}

  • If Group B streptococcus is isolated from a swab or if erythromycin is contra-indicated then penicillin or clindamycin is usually recommended.⁷

• Tocolytics - eg, atosiban, nifedipine or ritodrine - are no longer recommended, as they do not significantly improve perinatal outcome.

• Amnioinfusion is not currently recommended for routine clinical management of P-PROM.⁸

• Antenatal steroids should be given if gestation is between 24⁺⁰and 34⁺⁶ weeks.

• Antenatal steroids should be discussed in those with a gestation between 22 and 23⁺⁶ taking into account individual circumstances.

• Antenatal steroids are associated with a significant reduction in rates of neonatal death, respiratory distress syndrome and intraventricular haemorrhage and are safe for the mother.⁵

• Women who have P-PROM and are in established labour, or are having a planned preterm birth within 24 hours, should be offered intravenous magnesium sulfate between 24+0 and 29+6 weeks of gestation.²

Delivery or expectant management?

NICE guidelines for induction of labour recommend that:⁹

• Before 34+0 weeks do not offer induction unless there are additional obstetric indications (for example, infection or fetal compromise). Offer expectant management until 37+0 weeks.

• After 34+0 weeks, but before 37+0 weeks, discuss the options of expectant management until 37+0 weeks, or induction of labour with her.

• After 34+0 weeks (but before 37+0 weeks), with a positive group B streptococcus test at any time in their current pregnancy, offer immediate induction of labour or caesarean birth.

Premature rupture of membranes complications³

• The three main causes of neonatal mortality associated with P-PROM are prematurity, sepsis and pulmonary hypoplasia.

• Umbilical cord prolapse.

• Placental abruption.

• (Early in pregnancy) may lead to oligohydramnios.

• Increased incidence of retained placenta and primary and secondary postpartum haemorrhage.

Prevention

Both intravaginal progesterone and cervical cerclage are used prophylactically to prevent P-PROM in different circumstances, although evidence is lacking on which is more effective and the relative costs and benefits of each. In the UK, NICE has the following recommendations for women who, on a transvaginal ultrasound scan between 16⁺⁰ and 34⁺⁰ weeks, have a cervical length of <25 mm:⁵

• Women who have previously had a preterm birth or pregnancy loss between 16⁺⁰ and 34⁺⁰ weeks, should be offered either intravaginal progesterone or cervical cerclage.

• Women with no history of a preterm birth or pregnancy loss between 16⁺⁰ and 34⁺⁰ weeks, should be offered intravaginal progesterone.

• Women who have had P-PROM in a previous pregnancy or have a history of cervical trauma, should be offered cervical cerclage.