PREMATURE RUPTURE OF MEMBRANES & CHORIOAMNIONITIS
Premature rupture of membranes (PROM) is
pres-ent when leakage of amniotic fluid occurs before the onset of labor. The
pH of amniotic fluid causes Nitrazine paper to change color from blue to
yellow. PROM complicates 10% of all pregnancies and up to 35% of premature
deliveries. Predisposing fac-tors include a short cervix, prior history of PROM
or preterm delivery, infection, multiple gestations, polyhydramnios, and
smoking. Spontaneous labor commences within 24 h of ruptured membranes in 90%
of patients. Management of PROM balances the risk of infection with the risk of
fetal prematu-rity. Delivery is usually indicated sometime after 34 weeks of
gestation. Patients with a gestation of less than 34 weeks can be managed
expectantly with prophylactic antibiotics and tocolytics for 5–7 days to allow
some additional maturation of fetal organs. The longer the interval between
rupture and the onset of labor, the higher the incidence of chorioam-nionitis.
PROM also predisposes to placental abrup-tion and postpartum endometritis.
Chorioamnionitis represents infection of the
chorionic and amnionic membranes, and may involve the placenta, uterus, umbilical
cord, and fetus. It complicates up to 1–2% of pregnancies and is usually but
not always associated with ruptured membranes. The contents of the amniotic
cavity are normally sterile but become vulnerable to ascending bacterial
infection from the vagina when the cervix dilates or the membranes rupture.
Intraamniotic infections are less commonly caused by hematog-enous spread of
bacteria or retrograde seeding through the fallopian tubes. The principal
maternal complications of chorioamnionitis are premature or dysfunctional
labor, often leading to cesarean section, intraabdominal infection, septicemia,
and postpartum hemorrhage. Fetal complications include acidosis, hypoxia, and
Clinical signs of chorioamnionitis include
fever (>38°C), maternal and fetal
tachycardia, uterine tenderness, and foul-smelling or purulent amniotic fluid.
Blood leukocyte count is useful only if mark-edly elevated because it normally
increases during labor (normal average 15,000/μL). C-reactive pro-tein levels are usually
elevated (>2 mg/dL). Gram stain of amniotic fluid obtained by amniocentesis is
helpful in ruling out infection.
The use of regional anesthesia in patients
with chorioamnionitis is controversial because of the the-oretical risk of
promoting the development of men-ingitis or an epidural abscess. Available
evidence suggests that this risk is very low and that concerns may be
unjustified. Moreover, antepartum antibiotic therapy appears to reduce maternal
and fetal mor-bidity. Nonetheless, concerns over hemodynamic stability
following sympathectomy are justified, particularly in patients with chills,
high fever, tachy-pnea, changes in mental status, or borderline hypo-tension.
In the absence of overt signs of septicemia, thrombocytopenia, or coagulopathy,
most clinicians offer regional anesthesia to those patients with
cho-rioamnionitis who have received antibiotic therapy.