last authored: Dec 2012, David LaPierre
Normally, rupture of membrane (ROM) occurs spontaneously after or with the onset of labor close to term delivery. Premature rupture of membranes (PROM) occurs prior to onset of labor when the fetus is over 37 weeks gestation; if ROM occurs under 37 weeks, it is termed preterm premature rupture of membranes (PPROM). Rupture is prolonged if it persists for more than 24 hours prior to the onset of labor. Both PROM and PPROM result in increased risk to mother and baby.
PROM occurs in 10% of all pregnancies, 8% occur at term and 2-3.5% at preterm pregnancies. It is responsible for almost 1/3 of preterm births. Almost 90% of woman who are at term will go into labor 24 hours after PROM. Of women with PPROM, approximately half will go into labour within 24 hours, and 70-80% will begin labour within one week.
Unlike in term infants, the risk of amniotic infection among premature does not increase with the time interval between rupture and birth. This is true when the infection is already present at the time of ROM and the infection itself could have triggered the onset of labor.
Mrs. H presents to Labour and Delivery at 33 weeks gestation, concerned that 'her waters might have broken".
Normally, cells of amniotic membrane are programmed to die at term. Cell death activates collagenase, a catabolic enzyme that leads to degradation of the membranes.
Mechanical forces contributed by the descending foetus/foetuses add to ROM. This same process probably occurs in PPROM, only prematurely.
Some pathologic factors such as infection cause inflammation of the membranes and increase the likelihood of damage. However, infection in some cases may be a consequence of PPROM and not its cause.
Causes for PROM and PPROM include:
Risk factors include:
A careful history is important in determining likelihood of PROM or PPROM.
Take note of:
Vitals of mother and baby should be taken, with particular attention to:
Digital exam should be avoided due to risk of ascending infection.
Sterile speculum exam is helpful for a number of reasons:
Assess for GBS status. In a woman who has had preterm birth, screening for bacterial vaginosis is indicated.
Rupture of membranes may be assessed in a number of ways via sterile speculum exam:
Visual inspection includes looking for pooling in the posterior fornix. Asking the woman to cough (Valsalva maneuver) may allow visualization of amniotic fluid leaking from the cervical os.
Sample fluid from posterior fornix and place on slide; let air dry for 10 minutes and examine, unstained, under a microscope.
Sample fluid from posterior fornix. Normal vaginal pH is 4.5- 6.0. Amniotic fluid pH is 7.1 - 7.3. False positive tests can occur with blood, vaginal infections, alkaline urine, and semen. High negative predictive value
Helpful between 24-34 weeks to predict risk of preterm labour.
Place in the posterior fornix for 10 seconds. Wait 30-120 minutes for result.
Predictor of preterm deliver in 7-14 days.
A high WBC count with dominance of neutrophils may suggest intra-uterine infection, eg chorioamnionitis. The evidence to support the use of CRP for the early diagnosis of chorioamnionitis remain unclear, but a high CRP level may give weight to this diagnosis.
Fetal ultrasound may be carried out for:
Transvaginal ultrasound can be done to measure cervical effacement.
<2.5 cm under 28 weeks suggests increased risk of preterm birth.
The differential for rupture of membranes includes:
If a woman who is at risk for cord prolapsed (ie known absence of head engagement) ruptures her membrane; there is a high risk of cord prolapse. This woman should call for help, position herself on hands and knees, and be urgently evaluated for prolapse.
Management of PROM and PPROM includes:
Corticosteroids should be given to mature lungs at 24-34 weeks of gestation. A single course of antenatal corticosteroids should be administered to women with PROM before 32 weeks of gestation to reduce the risks of respiratory distress syndrome (RDS), perinatal mortality, and other morbidities. The efficacy of corticosteroid use at 32–33 completed weeks is unclear based on available evidence, but treatment may be beneficial particularly if pulmonary immaturity is documented.
Expectant management reduces risk of prematurity but increases risk of intraunterine infection.
PROM: Induction of labour (with oxytocin or prostaglandin) is recommended for term pregnancies, using oxytocin or prostaglandin.
PPROM 34-37 weeks: induction is recommended
PPROM < 34 weeks: expectant management is usually preferred, with efforts to prolong pregnancy. Important considerations include:
For PPROM < 32 weeks: delivery is delayed until 33 completed weeks as long as there are no maternal or fetal complications;
Provide GBS prophylaxis if status is unknown.
Complications from PROM include:
Complications of PPROM include: