Premature
Rupture of Membranes
Amniotic fluid is normally
produced continuously, and after approximately 16 weeks’
gestation is pre-dominantly dependent on fetal urine production. However,
passage of fluid across the fetal membranes, across the skin, and across the
umbilical cord, as well as fetal saliva production and fetal pulmonary
effluent, also contribute. Amniotic fluid protects against infection, fetal
trauma, and umbilical cord compression. It also allows for fetal move-ment and
fetal breathing, which, in turn, permits fetal lung, chest, and skeletal
development. Decreased or absent amni-otic fluid can lead to compression of the
umbilical cord and decreased placental blood flow. Disruption (rupture) of the
fetal membranes is associated with loss of protective effects
and developmental roles of amniotic fluid.
Premature rupture of membranes
(PROM) is the
rup-ture of the chorioamnionic membrane before the onset of labor. PROM
occurs in approximately 12% of all pregnancies. PROM is associated with about
8% of term pregnancies (37 weeks or more of gestational age) and is generally
fol-lowed by the onset of labor. Preterm
PROM, defined asPROM that occurs before 37 weeks of gestation, is a leading
cause of neonatal morbidity and mortality, and is associated with approximately
30% of preterm deliveries. PROM leading topreterm delivery is associated
with neonatal complications of prematurity such as respiratory distress
syndrome, intra-ventricular hemorrhage, neonatal infection, necrotizing
enterocolitis, neurologic and neuromuscular dysfunction, and sepsis. The major complication of PROM is
intrauterineinfection. The presence of lower genital tract infectionswith Neisseria gonorrhoeae and group B
streptococcus as well as bacterial vaginosis increase the risk of intrauterine
infec-tion associated with PROM. Other complications include prolapsed
umbilical cord and abruptio placentae.
Consequences of preterm PROM
depend on the gestational age at the time of occurrence. Midtrimester
preterm PROM (between 16 and 26
weeks of gestational age) complicates about 1% of all pregnancies. PROM that
occurs early in pregnancy following midtrimester genetic amniocentesis is very
likely to seal with reaccumulation of amniotic fluid. Persistent
oligohydramnios at <22 weeks of gestation is associated with incomplete
alveolar devel-opment and the development of pulmonary hypoplasia. Survival is likely in the 24-week to 26-week
group, although the morbidities of extreme prematurity in this group of
neonates are more substantial. Infants born with pulmonary hypoplasiacannot
be adequately ventilated, regardless of the gestational age at birth, and soon
succumb to hypoxia and barotrauma from high-pressure ventilation.
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