Additional antibiotic use is associated with preterm birth among women with GBS bacteriuria

Abstract

WOMEN WITH GBS BACTERIURIA BRENNA ANDERSON, HYAGRIV SIMHAN, KATHRYN SIMONS, HAROLD WIESENFELD, Brown University, Obstetrics and Gynecology, Providence, Rhode Island, University of Pittsburgh, Obstetrics, Gynecology, and Reproductive Sciences, Pittsburgh, Pennsylvania OBJECTIVE: Use of antibiotics among unselected pregnant populations has been associated with adverse pregnancy outcome. Our objective was to determine the risk of preterm birth related to antibiotic use among women with Group B Streptococcal (GBS) bacteriuria. STUDY DESIGN: A retrospective cohort analysis was performed. All women with GBS bacteriuria who registered with a hospital-wide research registry were included. Controls were women with negative urine cultures. The impact of the use of any antenatal antibiotics in addition to those used to treat GBS bacteriuria was assessed. Logistic regression analysis was used to determine the risk of preterm birth among bacteriuric women who received ‘‘other antibiotics’’. RESULTS: There were 423 women included in the analysis. 203 women with GBS bacteriuria and 220 women with negative cultures were included. There were no differences in most demographic characteristics between the groups. The women with GBS bacteriuria tended to have higher body mass indices and later gestational age at collection of urine sample. The mean gestational age at delivery was 38.3 weeks among all study subjects. There were no differences in rates of preterm birth, premature rupture of membranes, or endometritis between the bacteriuric and non-bacteriuric groups. The frequency of preterm birth was 16% (35/185) in the non-bacteriuric controls, 16% (19/120) in those with GBS bacteriuria not receiving additional antibiotics, and 28% (23/83) among those with GBS bacteriuria who received antibiotics for ‘‘other indications’’. In a stratified analysis, among women with GBS bacteriuria, the risk of preterm birth was increased with the use of ‘‘other antibiotics’’, independent of treatment for bacteriuria and potential confounding variables (adjusted odds ratio, 2.7; 95% confidence interval, 1.2-6.1). CONCLUSION: Among women with GBS bacteriuria, the risk of preterm birth is increased with exposure to additional antibiotics independent of treatment for bacteriuria. This may be related to alteration in vaginal flora.