Premature Rupture of Membranes

Synonym: Pre-labour rupture of membranes

Premature rupture of membranes (PROM) is the rupture of the membranes prior to the onset of labour.
Preterm premature rupture of the membranes is the rupture of membranes prior to the onset of labour in a patient who is at less than 37 weeks gestation.
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.¹

Pre-labour rupture of the membranes occurs in 6-19% of term pregnancies.²
Pre-term premature rupture of membranes occurs in 2% of all pregnancies.³

Risk factors

Risk factors for pre-term premature rupture of membranes are:

• Smoking
• Previous preterm delivery
• Vaginal bleeding at any time during the pregnancy

Mother may give history of a 'popping sensation', or a 'gush' with continuous watery liquid draining thereafter.
Underwear or pad may be damp.

• Diagnosis of rupture of membranes:
  • Actually seeing amniotic fluid draining from the cervix is the most accurate test. Sterile speculum examination: check for liquor and umbilical cord.
  • Nitrazine test may help to confirm the diagnosis. Urine, semen and other contaminants may give a false positive test result.
  • Regular pad checks
• Ultrasound to check for gestation and liqour volume.
• Temperature monitoring at least 12-hrly for ascending infection:
  • High vaginal swab
  • If infection suspected, check full blood count, CRP, MSU and blood cultures; start broad spectrum antibiotic
• Fetal monitoring

Refer urgently to hospital if:

• Preterm premature rupture of membranes is suspected.
• Ascending infection is suspected: maternal or fetal tachycardia, temperature, abdominal tenderness.

Antibiotic administration

This is associated with a delay in delivery and a reduction in major neonatal morbidity.
Co-amoxiclav should be avoided in women at risk of preterm delivery because of the increased risk of neonatal necrotising enterocolitis.
Therefore erythromycin may be a better choice.⁴ The recommended dose is 250mg qds for 10 days.³

Delaying premature birth

The following factors have been shown to be significantly associated with pre-term delivery:⁵

• Low body mass index
• Maternal pulmonary disease
• Onset of contractions within 2 weeks of PROM
• Short cervix (≤25 mm)
• Positive results of fetal fibronectin screening
• Bacterial vaginosis
• Previous preterm birth caused by premature rupture of membranes (in multiparous women)

The overall outcome for the neonate depends on gestational age. The prognosis improves with gestational age, especially between 24 and 27 weeks and so prolonging the pregnancy is beneficial in such cases.⁶
Tocolytics, e.g. atosiban, nifedipine or ritodrine, may delay delivery by 48 hours and therefore enable time for antenatal corticosteroids to be given. They should only be considered in the presence of uterine activity.
Antenatal steroids should be given if gestation is between 24 and 36 weeks. Dexamethasone accelerates fetal surfactant production and lung maturation. Antenatal steroids have been shown to reduce respiratory distress syndrome, intraventricular haemorrhage and mortality by 40%.⁷

Delivery or expectant management?

Consider delivery if:

• Evidence of ascending infection, fetal distress or gestation over 34 weeks; evidence shows that expectant management of women at 34 weeks and beyond is of limited benefit.⁸
• Women with pre-labour rupture of the membranes at term (over 37 weeks) should be offered a choice of immediate induction of labour or expectant management.
• For a pregnancy that has reached term, if emergency admission is not required within the first 72 hours after admission, woman can be managed at home with outpatient monitoring for infection and fetal well-being.
• However it is recommended that women with pre-labour rupture of the membranes at term should not exceed 96 hours following membrane rupture.² The increase in risk of maternal and fetal infection increases with increasing time between the rupture of membranes and the onset of labour.

• May lead to operative delivery and/or low five-minute Apgar score²
• Pre-term delivery
• Ascending infection (incidence is 30%; neonatal sepsis occurs in 2-4%)
• Umbilical cord prolapse
• Placental abruption
• Rupture of membranes early in pregnancy may lead to oligohydramnios, causing pulmonary hypoplasia in the neonate.
• Increased incidence retained placenta, and primary and secondary postpartum haemorrhage
• Rupture of vasa praevia with likely resultant fetal exsanguination (fetal mortality 33-100%)

Controversial subject with debate between those wary of potential complications and unnecessary intervention against those with equal concerns for the benefits, when indicated, of closer monitoring of the baby and avoidance of excessively long labour.

Indications

• Induction of labour
• Augmentation (speed up) labour
• Fetal monitoring in labour: monitoring liquor, fetal scalp electrode, fetal blood sample

Complications

• Increased pain to the mother
• Fetal distress
• Maternal or fetal sepsis
• Cord prolapse
• Wrong dates - prematurity
• Rupture of vasa previa with likely resultant fetal exsanguination (fetal mortality 33-100%)