Group B Streptococcus prevalence in pregnancy and maternal-fetal transmission: A multicenter study

Objective: To evaluate the prevalence of Streptococcus agalactiae (GBS) in pregnancy and the rate of transmission to the newborns. Material and Methods: 7176 consecutive mother-newborn pairs from single pregnancies were analyzed in 23 Italian hospitals. Vaginal and/or rectal swabs in labor and, in some cases, during pregnancy and swabs from infants at birth were collected in a 3-month period. Results: At delivery, vaginal (9.8%) was slightly greater than rectal (7.9%) colonization. Vaginal carrier status ranged from 3.7% to 22% in the various centers. No relation was found between GBS prevalence and sample size or geographical localization. The prevalence was similar to that in recent italian literature, the figures being lower than those reported in other countries. Conclusions: In pregnancy (36 weeks of gestation) the prevalence of GBS was greater (12.1%) than at delivery (10.7%) and rectal (11.1%) was more frequent than vaginal (9.8%) colonization. Vertical transmission of GBS to newborns occurred in 43.2% of culture-positive untreated women. Three newborns developed early onset sepsis; their mothers were all colonized and remained untreated.