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Am Fam Physician. 2003;68(10):2068-2070

Preterm birth has been linked to maternal bacterial vaginosis, possibly because of the hostile fetal environment created by related subclinical endometritis. Small studies of systemic and vaginal antibiotics have indicated that treatment of bacterial vaginosis improves pregnancy outcomes, but results are inconsistent. Ugwumadu and colleagues reasoned that systemic therapy would be necessary to address endometritis and that treatment early in pregnancy would be required to provide the best environment for the developing fetus.

The study group conducted a randomized clinical trial including more than 6,000 pregnant women with bacterial vaginosis to assess the impact of systemic clindamycin treatment on pregnancy outcomes. All women attending two English teaching hospitals for their first antenatal visit during a three-month period were offered screening for bacterial vaginosis and participation in the study.

Patients included in the study were at 12 to 16 weeks of gestation and had no contraindications, such as multiple pregnancy; uterine, cervical, fetal, or systemic disorders; or inability to take clindamycin. Ultrasonography was used to confirm gestational age and exclude major fetal and uterine pathologies. The 494 eligible women with abnormal vaginal flora or overt bacterial vaginosis on screening of vaginal secretions were allocated randomly to clindamycin (300 mg twice daily for five days) or identical placebo. Patients were monitored at clinic visits for pregnancy complications, miscarriage, preterm birth, and adverse effects. Data were collected on gestational age and condition of the infant at delivery.

The treatment and placebo groups were similar at randomization. Five women were lost to follow-up, and four women electively terminated their pregnancies. Eleven (5 percent) of the women treated with clindamycin had spontaneous preterm deliveries compared with 28 (12 percent) in the placebo group. The treated group also had fewer late miscarriages. Overall, 91 percent of women in the treatment group and 83 percent in the placebo group delivered at term. Mean gestational age and birth weight did not differ significantly between the groups. The effect of clindamycin therapy in reducing miscarriage and preterm delivery was greatest in women with the most severe bacterial vaginosis infection.

The authors conclude that oral clindamycin therapy used early in the second trimester of pregnancy significantly reduces preterm birth and late miscarriage, especially in women with more severe infections.

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