Double-Blind Placebo-Controlled Treatment Trial of Chlamydia trachomatis Endocervical Infections in Pregnant Women.

Objective: The purpose of this study was to determine if treatment of pregnant women with Chlamydia trachomatis infection would lower the incidence of preterm delivery and/or low birth weight.

Methods: Pregnant women between the 23rd and 29th weeks of gestation were randomized in double-blind fashion to receive either erythromycin 333 mg three times daily or an identical placebo. The trial continued until the end of the 35th week of gestation.

Results: When the results were examined without regard to study site, erythromycin had little impact on reducing low birth weight (8% vs. 11%, P = 0.4) or preterm delivery (13% vs. 15%, P = 0.7). At the sites with high persistence of C. trachomatis in the placebo-treated women, low birth weight infants occurred in 9 (8%) of 114 erythromycin-treated and 18 (17%) of 105 placebo-treated women (P = 0.04) and delivery <37 weeks occurred in 15 (13%) of 115 erythromycin-treated and 18 (17%) of 105 placebo-treated women (P = 0.4).

Conclusions: The results of this trial suggest that the risk of low birth weight can be decreased by giving erythromycin to some women with C. trachomatis. Due to the high clearance rate of C. trachomatis in the placebo group, these data do not provide unequivocal evidence that erythromycin use in all C. trachomatis-infected women prevents low birth weight.