Definitions
- Premature rupture of the membranes (PROM) refers to rupture of the fetal membranes before the onset of labor.
- Preterm PROM (PPROM) refers to PROM at <37 weeks.
- Prolonged PROM refers to PROM >24 hours and is associated with an increased risk of intra-amniotic infection.
Diagnosis
- PROM is a clinical diagnosis (Figure 59.1).
- If clinical examination is equivocal and the pregnancy is remote from term, US practice favors an amnio-dye test (“tampon test”) in which indigo carmine dye (not methylene blue because of an association with fetal methemoglobinemia) is instilled into the amniotic cavity, and leakage into the vagina confirmed by staining of a tampon within 20–30 min.
- Differential diagnosis. Leakage of urine, vaginal discharge.
Latency
- Latency refers to the interval between PROM and delivery.
- Of women with PROM at term 50% will go into labor within 12 hours, 70% within 24 hours, 85% within 48 hours, and 95% within 72 hours.
- Latency is influenced by gestational age (50% of women with PPROM will go into labor within 24–48 hours and 70–90% within 7 days), severity of oligohydramnios (severe oligohydramnios is associated with shortened latency), and multiple pregnancy (twins have a shorter latency period than singletons).
Etiology
- Near term, a focal weakness develops in the fetal membranes over the internal cervical os which predisposes to rupture at this site.
- Several pathologic processes (including bleeding, infection) may predispose to PPROM.
Term premature rupture of the membranes
Incidence
This is 8–10% of term pregnancies.
