Chorioamnionitis May Not Mandate C-Section


MONTEREY, CALIF. — By itself, chorioamnionitis does not justify an operative delivery even if the first stage of labor is prolonged, a retrospective study of 1,810 deliveries suggests.

Longer first-stage labor in pregnancies with chorioamnionitis was associated with a 60% increased risk for cesarean delivery and a 30% increased risk for meconium-stained amniotic fluid, a multivariate analysis found. The results showed no increase in risk for meconium aspiration syndrome with prolonged first-stage labor in pregnancies with chorioamnionitis, Dr. Natali Aziz said at the annual meeting of the Infectious Diseases Society for Obstetrics and Gynecology.

Chorioamnionitis in previous studies has been associated with significant adverse obstetric and neonatal outcomes including maternal blood loss and transfusions, endomyometritis, greater severity of lacerations, meconium aspiration syndrome, lower Apgar scores, neonatal sepsis, and other problems.

The current study found that the duration of first-stage labor in women with chorioamnionitis did not affect the risk of neonatal sequelae, “which was surprising to us,” said Dr. Aziz of the University of California, San Francisco.

The timing of delivery for patients with chorioamnionitis is controversial, she said. Her institution does not deliver based solely on the diagnosis of chorioamnionitis, but some other institutions do.

The investigators analyzed outcomes by comparing women with chorioamnionitis whose first stage of labor lasted less than 12 hours (39% of cases), 12–24 hours (48%), or 24 hours or longer (13%). The results “support continued efforts to achieve a vaginal delivery if other obstetrical indications permit, even in the setting of a prolonged course of labor and intraamniotic infection,” Dr. Aziz said. “Much of the maternal morbidity in our data was due to operative delivery in itself.”

An initial univariate analysis found that a longer first-stage labor was associated with worse maternal and obstetric outcomes, but “not as much as we expected,” she said. Risks for postpartum hemorrhage, C-section, endomyometritis, and operative vaginal delivery increased with longer labors.

Postpartum hemorrhage and endomyometritis, however, can be associated with cesarean delivery, so the investigators conducted a multivariate analysis that controlled for the effects of potential confounders, including cesarean delivery. That analysis found associations only between longer labor and increased risks for cesarean delivery or meconium-stained amniotic fluid.

They then conducted a second multivariate analysis that did not control for the effects of cesarean delivery. Some researchers have speculated that cesarean delivery may be a causal pathway that leads from chorioamnionitis to adverse perinatal outcomes, and so controlling for cesarean delivery might mask any effects of prolonged labor on chorioamnionitis and neonatal outcomes, Dr. Aziz and her associates reasoned.

In the analysis that did not control for cesarean delivery, the only other significant association with increased duration of first-stage labor was a 20% increased risk for postpartum hemorrhage. There was a trend toward greater need for blood transfusion with prolonged first-stage labor in pregnancies with chorioamnionitis. “We've demonstrated that the increasing duration of first-stage labor was associated with increased maternal morbidity, and in turn with operative delivery and thereby postpartum hemorrhage, but not with neonatal morbidity,” she said.

One physician in the audience commented, “I think these are very encouraging and reassuring data.”

Prolonged first-stage labor in pregnancies with chorioamnionitis also was associated with a significantly decreased risk for an umbilical artery base excess greater than 12 mmol/L, which puzzled the investigators. This may be due to fetal indications causing the delivery, Dr. Aziz said.

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