BACTERIAL VAGINOSIS AND INTRAAMNIOTIC INFECTION

OBJECTIVE: We sought to determine the predictors of intraamniotic infe ction with use of the presence or absence of vaginal microbes and clin ical variables. STUDY DESIGN: Vaginal fluid was collected and analyzed on 936 of 2711 (35%) consecutive patients who were delivered over a 7 -month period. Subjects were followed up prospectively for the develop ment of intraamniotic infection. Intraamniotic infection was defined a s an intrapartum fever >37.8 degrees C plus at least two of the five f ollowing variables: maternal or fetal tachycardia, leukocytosis, tende r uterus, or foul-smelling amniotic fluid. Bacterial vaginosis score a nd the presence or absence of aerobic vaginal organisms were independe nt microbial variables. Demographic, maternal, labor, and delivery cha racteristics were independent clinical variables. Stepwise logistic re gression analysis was used to develop adjusted odds ratios for predict ing intraamniotic infection (expressed as odds ratio [95% confidence i nterval]). Selection bias and microbiologic reliability were measured. RESULTS: A bacterial vaginosis score of 7 to 10 (odds ratio 1.7, [95% confidence interval 1.9 to 3.9]), nulliparity (2.1 [1.3 to 3.4]), eac h hour of internal fetal electrode (1.2 [1.0-1.3]); and, each vaginal examination (1.7 [1.0-3.9]) were predictors of intraamniotic infection . Selected aerobic vaginal organisms such as group B streptococci or g ram-negative rods were not predictive. Reanalysis with a bacterial vag inosis score greater than or equal to 4 revealed similar predictors of intraamniotic infection. Bacterial vaginosis had an adjusted odds rat io of 1.85 (1.16 to 2.9). Selected higher risk populations, vaginal ex aminations greater than or equal to 6 (n = 365), or rupture of membran es greater than or equal to 7 hours (n = 421) did not change the risk of a bacterial vaginosis score greater than or equal to 4 (adjusted od ds ratio 1.87 and 1.98, respectively). CONCLUSION: Abnormal vaginal fl ora combines with clinical variables to increase the risk of intraamni otic infection.