Preterm prelabour rupture of membranes

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Chapter 36 Preterm prelabour rupture of membranes

Justin Nasser

Definitions. Prelabour (premature) rupture of membranes (PROM) refers to membrane rupture before the onset of uterine contractions irrespective of gestational age. Preterm prelabour rupture of membranes (PPROM) refers to membrane rupture before the onset of uterine contractions in a pregnancy that is <37 completed weeks of gestation.

Incidence. PROM occurs in 10% of all pregnancies. PPROM occurs in 3% of pregnancies and is responsible for, or associated with, approximately one-third of preterm births.

Aetiology of PPROM

• The pathogenesis of PPROM is poorly understood and in the majority of cases the exact aetiology is unknown.
• There are multiple possible aetiologies that probably share a common final pathway leading to membrane rupture. Such factors include those leading to membrane stretch, membrane degradation, uterine contractility, local inflammation, and increased susceptibility to ascending genital tract infection.

Risk factors of PPROM

• past history of PPROM/preterm delivery
• urogenital tract infection/colonisation
• antepartum haemorrhage
• cigarette smoking
• past history of cervical surgery
• amniocentesis in current pregnancy
• cervical length ≤25 mm
• positive fetal fibronectin (fFN)
• connective tissue disorders
• nutritional deficiencies
• lean maternal body mass
• multiple pregnancy/polyhydramnios

Most cases of PPROM occur in women without risk factors and there is currently no reliable way of predicting and preventing PPROM.

Clinical significance of PPROM

Both mother and fetus are at risk from complications associated with PPROM.

Maternal risks

• those associated with infection, including chorioamnionitis, endometritis and septicaemia

• risk of intrauterine infection increases with duration of membrane rupture
• clinical signs indicating chorioamnionitis include maternal pyrexia, tachycardia, leucocytosis, uterine tenderness, offensive vaginal discharge and fetal tachycardia

• those associated with operative delivery, which is more likely in the setting of PPROM

Fetal risks

• preterm delivery

• most cases of PPROM will deliver within 1 week after membrane rupture; however, latency increases with decreasing gestational age
• morbidities associated with preterm delivery: hyaline membrane disease, intraventricular haemorrhage, periventricular leukomalacia and other neurologic sequelae, infection (e.g. sepsis, pneumonia, meningitis), necrotising enterocolitis and retinopathy of prematurity; rates vary with gestational age and are increased by the presence of chorioamnionitis

• pulmonary hypoplasia: hydrostatic pressure from amniotic fluid is essential to lung development and maturation in the mid-second trimester; loss of amniotic fluid at this stage of development can irreversibly arrest lung development and result in pulmonary hypoplasia; associated with significant neonatal mortality regardless of gestational age at birth
• musculoskeletal/facial deformities: due to the reduction in amniotic fluid and restriction of fetal movement
• malpresentation
• placental abruption
• umbilical cord complications (e.g. compression, prolapse)

Diagnosis

In the majority of cases, the diagnosis can be confidently made based on a history of fluid loss per vagina and direct visualisation of amniotic fluid in the posterior fornix by sterile speculum examination. If amniotic fluid is not immediately visible, fluid leakage through the internal os can be provoked by the Valsalva manoeuvre or coughing. Repeat speculum examination after a period of recumbency may assist the diagnosis.

A number of ancilliary tests with varying degrees of sensitivity/specificity and false-positive/false-negative rates can be used to assist in the diagnosis. These include:

• nitrazine test
• ferning/arborisation
• AmniSure test
• other biochemical tests (fFN, alopha-fetoprotein (AFP), diamino-oxydase, prolactin, human chorionic gonadotrophin (hCG))
• ultrasound assessment of amniotic fluid volume
• intra-amniotic indigo carmine with passage of blue fluid per vagina

Other causes of fluid loss include leucorrhoea, urinary incontinence, vaginitis, cervicitis, mucus show, semen and vaginal douches.

Management of PPROM

The management of PPROM is determined by several factors, including:

• gestational age
• available obstetric and neonatal services
• presence/absence of maternal/fetal infection
• presence/absence of labour and/or cervical changes
• fetal presentation
• assessments of fetal wellbeing

These factors need to be considered in each case and a decision made as to whether conservative or aggressive management is most appropriate.

Delivery is indicated when the risk to the fetus of complications of prematurity are outweighed by the risks to the mother/fetus of complications of PPROM.

Initial management

• The initial management involves confirming the diagnosis by history and clinical examination. At the time of sterile speculum examination, endocervical swabs (Chlamydia, gonorrhoea) and ano-vaginal swabs (group B streptococcus) should be collected.
• Digital examinations should be avoided unless delivery is anticipated.
• Generally, expeditious delivery is indicated if labour is advanced, or in the presence of non-reassuring fetal status and/or infective complications, regardless of gestational age. In the absence of these conditions, subsequent management is dependent on the gestational age at time of PPROM and the subsequent presence or absence of conditions necessitating delivery.

PPROM: 34–37 weeks

• The risk of serious neonatal complications with delivery after 34 weeks is low.
• There is no significant improvement in neonatal outcomes and an apparent increased risk of chorioamnionitis with expectant management in PPROM after 34 weeks.
• Current evidence suggests that delivery should be expedited to reduce the risk of associated complications when PPROM occurs near term.

PPROM: 24–33 weeks

• PPROM remote from term is generally managed in hospital due to a short latency period and high complication rate/intervention rate.
• Some studies have demonstrated favourable outcomes and cost savings with home management of selected cases after an initial period (48–72 hours) of hospital admission.
• In the absence of complications, ongoing observation, administration of corticosteroids and adjuvant antibiotics (see below), and serial monitoring, is indicated, with consideration for delivery occurring at 34 weeks.

PPROM: <23 completed weeks

• Good quality data to guide management in previable PPROM are sparse.
• Perinatal mortality is high and decreases with advancing gestation.
• More than half are delivered within 1 week of PPROM, either as a result of spontaneous labour or induced labour due to maternal/fetal indications.
• Induction of labour is achieved with either high-dose oxytocin or by vaginal/oral prostaglandins.
• After conservative management, approximately one-quarter will remain pregnant 1 month after membrane rupture. These women should be monitored for signs necessitating delivery.
• Depending on specific circumstances, outpatient management may be appropriate.
• Serial ultrasound assessments should occur to evaluate liquor volume and fetal growth. Ultrasound assessment of lung volumes (direct and indirect) is useful in predicting pulmonary hypoplasia.
• Persistent oligohydramnios following PPROM is associated with poorer outcomes regardless of gestational age at delivery.
• PPROM following amniocentesis is associated with more favourable outcomes.
• If the pregnancy reaches a stage where resuscitation of the newborn is planned, consideration should be given for in utero transfer to an institution with appropriate facilities for emergency delivery and neonatal intensive care.

Antenatal corticosteroids

• Antenatal corticosteroids significantly reduce the risks of respiratory distress syndrome, intraventricular haemorrhage and necrotising enterocolitis, without increasing the risks of maternal or neonatal infections in women with PPROM.
• The maximum benefit is in those fetuses between 28 and 32 weeks gestation.
• Data on the benefit of repeat weekly doses of corticosteroids, or administration of rescue steroids remote from initial course in women with PPROM who remain undelivered, are conflicting.

Adjuvant antibiotics

• Antibiotic therapy in women with PPROM is used in an attempt to treat/prevent ascending infection in order to prolong the latency period and reduce gestational-age-dependent morbidity and neonatal infections.
• Current data support erythromycin 250 mg orally four times daily for 10 days or until delivery following diagnosis of PPROM.
• The use of extended spectrum amoxycillin-clavulanic acid is associated with an increased risk of necrotising enterocolitis and is not recommended.
• Intrapartum antibiotics for group B streptococcus prophylaxis, and antibiotic therapy for chorioamnionitis/sepsis, should be considered in addition to the above regimen.

Tocolysis

• The benefit of tocolytic therapy in the setting of PPROM is unclear and is not routinely recommended. It is contraindicated in the presence of chorioamnionitis.
• As in the setting of preterm labour with intact membranes, tocolysis may have a role in delaying delivery in order to obtain maximum benefit of corticosteroids and allow in utero transfer to an appropriate facility for delivery.

Emerging therapies

• Various agents (gelatine sponge, platelets, cryoprecipitate, fibrin) have been used to form a cervical plug/act as a membrane sealant.
• Amnioinfusion has been used in an attempt to replace amniotic fluid.
• Current data are insufficient to recommend their implementation into routine practice.

Further reading

Canavan T., Simhan H., Caratis S. An evidence-based approach to the evaluation and treatment of premature rupture of membranes: part I. Obstetrical and Gynecological Survey. 2004;59(9):669-677.

Canavan T., Simhan H., Caratis S. An evidence-based approach to the evaluation and treatment of premature rupture of membranes: part II. Obstetrical and Gynecological Survey. 2004;59(9):678-689.

Kenyon S., Boulvain M., Neilson J.P. Antibiotics for preterm rupture of membranes. Cochrane Database of Systematic Reviews. (Issue 2):2003. Art. No.: CD001058. DOI: 10.1002/14651858

Mercer B.M. Preterm premature rupture of membranes: diagnosis and management. Clinics in Perinatology. 2004;31:765-782.

Morris J., Roberts C., Crowther C., et al. Protocol for immediate delivery versus expectant care of women with preterm prelabour rupture of membranes close to term (PPROMT) Trial [ISRCTN44485060]. BMC Pregnancy and Childbirth. 2006;6:9.

Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RACOG). Preterm premature rupture of membranes. Melbourne: RACOG; 2006. Guideline No. 44, November

Waters T.P., Mercer B.M. The management of preterm premature rupture of membranes near the limit of fetal viability. American Journal of Obstetrics and Gynecology. 2009;201(3):230-240.

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