Treatment of Asymptomatic BV Does Not Prevent Preterm Delivery

abstract & commentary

Synopsis: This study concludes that the treatment of asymptomatic BV in pregnant women does not reduce preterm delivery.

Source: Carey JC, et al. N Engl J Med 2000;342: 534-540.

To determine if the treatment of asymptomatic bacterial vaginosis (BV) with a 2 g dose of metronidazole at 16-24 weeks gestation and again at 24-30 weeks would reduce preterm births, 1953 women with BV based on a gram stain with a Nugent score of 7 and a vaginal pH higher than 4.4 were randomized to treatment with the active drug metronidazole or a placebo. The study group was recruited from a general obstetric population of primarily African-American and Hispanic patients. The average gestational age at randomization was 20 weeks. Women who received metronidazole were significantly more likely to have resolution of BV than the placebo group, 77.8% vs. 37.4%. However, there was no significant difference in the rate of preterm delivery in patients treated with metronidazole (12.2% vs 12.5%). Metronidazole did not reduce the rate of preterm births from spontaneous labor or spontaneous rupture of the membranes. Treatment with metronidazole did not decrease the rate of preterm delivery in any subgroup of women including those who had a prior preterm birth or those who were less than 20 weeks at randomization. Furthermore, metronidazole therapy did not reduce the rate of chorioamnionitis, postpartum endometritis, admissions to the neonatal intensive care unit, or neonatal sepsis.

Carey and colleagues conclude that the treatment of asymptomatic BV in pregnant women does not reduce preterm delivery.

COMMENT BY STEVEN G. GABBE, MD

BV has been associated with an increased risk for preterm birth and treatment of women with symptomatic BV is recommended. This important study by Carey et al was conducted to determine whether treatment of asymptomatic BV with metronidazole early in the second trimester and early in the third trimester would reduce the rate of preterm birth. While metronidazole was effective in clearing BV in nearly 80% of women treated, metronidazole did not reduce the rate of preterm birth or infectious morbidity in the mother or her infant. In the metronidazole group, nearly 30% of the women had a prior preterm delivery, while this figure was nearly 24% in the placebo group. Metronidazole did not reduce preterm births in these patients.

Could treatment of BV earlier in pregnancy or even before pregnancy have altered these results? That question remains unanswered. However, metronidazole is generally contraindicated in the first trimester. Oral clindamycin, 300 mg twice a day for seven days, or topical clindamycin vaginal cream, once daily for seven days, can be used to treat BV early in gestation.

The study by Carey et al demonstrated that treatment of asymptomatic BV with metronidazole in a general obstetric population reduced which one of the following?

a. Preterm birth

b. Preterm premature rupture of the membranes

c. Postpartum endometritis

d. Bacterial vaginosis

e. Neonatal sepsis