The Prevalence and Adverse Effects of Group B Streptococcal Colonization during Pregnancy

This study was done to evaluate the prevalence of rectovaginal colonization with group B streptococci among pregnant women who delivered in our center. Also maternal and neonatal complications were compared between colonized and noncolonized groups. Rectovaginal cultures were obtained from 1197 pregnant women with gestational ages greater than 24 weeks who were admitted to the labor room of Zeinabieh Hospital affiliated to Shiraz University of Medical Sciences from April to September 2003. All of the neonates had surface cultures after birth. The B streptococci carrier and noncarrier groups were compared for maternal and neonatal complications that occurred in the first week after delivery. Out of the 1197 pregnant women who were evaluated for B streptococci, 110 (9.1%) had rectovaginal colonization (group 1) and 1087 women were not colonized (group 2). Sixty-six neonates had positive B streptococci cultures after birth with a transmission rate of 60%. One neonate developed early-onset B streptococci sepsis. Out of the 110 women who had positive B streptococci culture, 40 (36.3%) developed preterm labor as compared with 155 (14.3%) out of the 1087 women in group 2 (P=0.001). The mean gestational age of newborns in group 1 was 32.8 ± 11 weeks compared with 36.2 ± 7.9 weeks for group 2 (P=0.001). Eighteen women (16.3%) in group 1 developed preterm rupture of membranes compared with 65 (6.0%) women in group 2 (P=0.001). Prolonged rupture of membranes was observed in 6.3% of women with B streptococci carrier states as compared with 0.5% in the second group (P=0.001). Intrapartum antibiotics were initiated primarily on the risk based strategy for 34 (30.9%) women in group 1 as compared with 12 (1.1%) in group 2 (P=0.001). There was one neonate with early-onset B streptococci sepsis born from a B streptococci carrier mother without any risk factor. Maternal complications were not different between the two groups. In this study 9.1% of the women had positive rectovaginal B streptococci cultures with a 60% transmission rate to their neonates. Also preterm birth, prolonged rupture of membranes, and preterm premature rupture of membranes had a higher incidence among B streptococci colonized mothers.