Chorioamnionitis in First Pregnancy May Recur in Second

DALLAS, Nov. 30 -- Women who develop chorioamnionitis during a first pregnancy have twice the risk for the amniotic infection in the next, researchers reported.

This supports the concept that chorioamnionitis may have a genetic component and should be further investigated, Vanessa Laibl, M.D., of the University of Texas Southwestern Medical Center here, and colleagues, wrote in the December issue of Obstetrics and Gynecology.

Chorioamnionitis occurs in 0.5% to 10% of births. It can cause bleeding and widespread infection in the mother and fetus, possibly resulting in intraventricular hemorrhage, periventricular leukomalacia, and cerebral palsy. Determining who is at risk for this condition might improve interventions and possibly neonatal and maternal outcomes, Dr. Laibl said.

In a large historical cohort study of 28,410 women who had their first and second deliveries of a single infant at Parkland Memorial Hospital in Dallas from 1988 to 2005, chorioamnionitis was diagnosed in 10% of the first-pregnancy index women. The index pregnancy was restricted to those who delivered vaginally, the researchers said.

The infected patients differed significantly from the rest of the cohort in terms of length of labor, length of second-stage labor, use of internal monitors, and prolonged rupture of membranes.

Of 2,891 deliveries in the second-pregnancy cohort, 5% of the index women again developed chorioamnionitis, compared with 2% of women who did not have the infection in the first pregnancy (OR=2.70 [2.26, 3.24]). After adjusting for the above confounders, the increased risk of recurrence persisted (OR=2.06 [1.70, 2.51]), Dr. Laibl said.

The second delivery included cesareans, but in a subsequent analysis, both pregnancies were restricted to vaginal births.

In this group, of the women with chorioamnionitis in the first pregnancy, 4.6% were diagnosed in the second pregnancy, compared with 1.9% of those without the infection in the first pregnancy. After adjusting for the confounders, the increased risk of recurrence remained (OR=2.00 [1.61, 2.47]), Dr. Laibl said.

In a separate analysis to adjust for maternal hypertension and diabetes, the researchers reported that after logistic regression and stratification of the results, with the exception of one grouping, after adjustments for prolonged membrane rupture, use of internal monitors, labor greater than 10 hours, hypertension, and diabetes, the association between the intra-amniotic infection in both pregnancies still held.

"Circumstances do play an important role," Dr. Laibl said, "but once you factor that out," women infected the first time remained more prone to infection in their second pregnancy.

"The patient's doctor should be vigilant about infection regardless of her previous pregnancy outcome," Dr. Laibl said. "That being said," she added, "there is no additional treatment to be done for the patient just because she had chorioamnionitis before."

Strengths of this study, the researchers said, included its large population followed over an extended period. All patients were managed in a similar manner, and by limiting the index pregnancy to a vaginal delivery, cesarean patients who would be at a lower risk for the infection were eliminated.

Study limitations included the fact that the actual number of vaginal exams, a known risk factor for the infection, was not available. Length of labor had to be used as a surrogate marker.

Patients were treated with antibiotics in accordance with hospital protocols, but there were no bacterial cultures of either the intrauterine cavity or the placenta. The intra-amniotic infection is polymicrobial, and cultures would not have aided in management.

The connection between chorioamnionitis during their first pregnancy and in the next pregnancy supports the concept of a genetic predisposition to intrauterine infection, the researchers said.

It has been suggested that the pro-inflammatory response associated with intra-amniotic infection is regulated genetically, Dr. Laibl said. Tumor necrosis factor (TNF-?) is a proinflammatory cytokine important in the infection cascade, she said, while other studies have shown that different polymorphisms in immunoregulatory genes may affect the likelihood of developing the infection.

If a genetic tendency to the infection is eventually identified, it could be extremely important in regard to counseling and management, the investigators added.

However, they said, this is only one possible theory. The risk could also be related to colonization of the upper and lower genital tract with more virulent bacterial organisms.

Further research is needed in this area to determine the etiologies involved, Dr. Laibl said. "Chorioamnionitis is likely a multifactorial complication influenced by a genetic component," she concluded.