Group B streptococci during pregnancy: a comparison of two screening and treatment protocols

The objective was to evaluate whether the rate of neonatal group B streptococcal infection could be reduced by screening for group B streptococci during the third trimester of pregnancy.

Two periods in which different screening and treatment protocols were applied were compared. In period A all mothers showing high-risk factors were given peripartal antibiotic coverage. In period B vaginal and rectal smears were routinely obtained in gestational week 34 and cultured for group B streptococci. If culture results were positive, the woman received peripartal antibiotics. The incidence of group B streptococcal infections and the number of peripartal antibiotic doses were established by comparing 3700 neonates (3623 mothers) in period A with 3648 neonates (3569 mothers) in period B.

In period A, 20 group B streptococcal infections were recorded. Of these, 5 were severe to life-threatening. In period B, 4 group B streptococcal infections were observed. Two were severe and occurred in neonates born before the mothers could be screened. Another 2 were mild and occurred in neonates whose mothers had negative screening test results. The reduction was significant by the chi2 test (chi2 = 9.19, Yates' corrected P = .0024). The rates of peripartal antibiotic treatment were 11.9% in period A and 14.5% in period B.

Although no neonate died of group B streptococcal sepsis in either of the 2 periods, the protocol used in period B clearly reduced the incidence of group B streptococcal infection. The number of peripartal antibiotic doses required was not much higher than in period A. Screening for group B streptococci in week 34 seems to be a valuable contribution to further improvement of neonatal outcome.