Objective -To find out whether women with bacterial vaginosis detected early in pregnancy are at increased risk of preterm delivery.
Design -Prospective description cohort study.
Setting -Antenatal clinic in a district general hospital.
Subjects -783 women examined during their first antenatal clinic visit and screened for recognised risk factors for preterm delivery and the presence of bacterial vaginosis or intermediate abnormal flora detected by examination of a vaginal smear stained by Gram's method.
Main outcome measures -Gestational age at delivery classified as late miscarriage (16-24 weeks' gestation), preterm delivery (24-37 weeks' gestation), term delivery (>37 or =37 weeks' gestation).
Results -Multiple logistic analysis showed that there was an increased incidence of preterm delivery in women with a previous preterm delivery (9/24; odds ratio 25; 95% confidence interval 9 to 70; P<0.001) and bacterial vaginosis (9/115; 2.8; 1.1 to 7.4; P=0.04). A further logistic analysis of data from women recruited before 16 weeks' gestation showed that preterm deliveries or late miscarriages occurred more often in women with bacterial vaginosis (12/77; 5.5; 2.3 to 13.3; P<0.001).
Conclusions -Late miscarriage and preterm delivery are associated with the presence of bacterial vaginosis in early pregnancy. This is independent of recognised risk factors such as previous preterm delivery.