Association between bacterial vaginosis and fetal fibronectin at 24-29 weeks' gestation

Objective: To investigate the relationship between fetal fibronectin and ba cterial vaginosis, which are associated with an increased risk for preterm delivery. Methods: Researchers for the Pregnancy, infection and Nutrition Study, a co hort study of pregnant women at three central North Carolina sites, collect ed genital tract specimens from all enrolled women between 24 and 29 weeks' gestation. Among women with last menstrual periods between March 10, 1995, and August 15, 1996, 868 pregnancies were eligible for this analysis. Feta l fibronectin was assessed by a dipstick immunoassay kit. Bacterial vaginos is was evaluated by Nugent-scored, Gram-stained vaginal smears (scores of 7 -10 considered positive). Results: Overall, 6.3% of women had positive fetal fibronectin test results , and 18.8% had bacterial vaginosis. The unadjusted relative risk (RR) of f etal fibronectin-positivity comparing women with bacterial vaginosis to tho se without bacterial vaginosis was 1.6 (95% confidence interval [CI] 1.1, 2 .5). Using multiple logistic regression to adjust for race, maternal age, p arity, and location of care, women who had bacterial vaginosis and smoked a t the time of recruitment were at substantially increased risk of fetal fib ronectin-positivity (RR 7.8, 95% CI 2.2, 27.8) compared with smokers withou t bacterial vaginosis. Among nonsmokers, bacterial vaginosis was not associ ated with fetal fibronectin-positivity (RR 1.0, 95% CI 0.4, 2.4). These res ults were essentially unchanged after adding the requirement of vaginal pH exceeding 4.5 to the bacterial vaginosis definition. Conclusion: Fetal fibronectin was associated positively with bacterial vagi nosis, but only among women who smoked. These results might provide clues a s to the biologic relationship between smoking, infection, and preterm deli very. (C) 1999 by The American College of Obstetricians and Gynecologists.