Oral Clindamycin and Histologic Chorioamnionitis in Women With Abnormal Vaginal Flora

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Abstract
Oral clindamycin reduced late miscarriage and preterm birth in asymptomatic women with bacterial vaginosis or intermediate flora. We investigated whether clindamycin reduced the incidence of histologic chorioamnionitis as a mechanism for these beneficial effects. This was a subanalysis of 126 participants from a larger randomized controlled trial. We compared the incidence of histologic chorioamnionitis between the clindamycin and placebo groups. Histologic chorioamnionitis was diagnosed by the presence of polymorphonuclear leukocytes, separately in the amnion and chorion, decidua, fetal surface of the placenta, the walls of fetal chorionic vessels, umbilical cord, or in the subchorionic fibrin layer. Microbiologic cultures were done on swabs from the space between the chorion and amnion layers. Histopathologic results were available for 122 placentas, 62 (51%) and 60 (49%) in the clindamycin and placebo groups, respectively. There were no significant differences in inflammation between the groups in the decidua (41% compared with 43%), membranes (25% compared with 41%), fetal vessels (16% compared with 14%), or subchorionic fibrin (32% compared with 34%). Adjusting for gestational age, ethnic origin, or history of miscarriage did not alter the results. There were no significant differences in the outcomes of pregnancy between women with and without inflammation, either before or after adjustment for treatment group. Although oral clindamycin reduced late miscarriage and preterm birth in women with abnormal vaginal flora, this effect is unlikely to be mediated through a reduction in the incidence of histologic chorioamnionitis. The relatively small size of the groups, however, does not allow us to rule out a real effect, especially given the lower rate of membrane inflammation observed in the clindamycin group. I.