Group B Streptococcus Screening

Group B Streptococcus (GBS) is a common bacterium found in women’s vagina and rectum. Although it is usually harmless to mothers, if the baby catches the bacterium during labour, it can cause a severe early onset infection in newborn infants including chest infection and meningitis. In Hong Kong, the incidence of early onset GBS infection in newborn is around 1.0 per 1000 births. The chance of a newborn getting GBS infection is much lower if the mother carrying the bacterium receives antibiotic injections during labour. It is for this reason that all expectant mothers are advised to have GBS screening between 35-37 weeks’ gestation. The screening test involves taking a swab from the lower part of the mother’s vagina and then the rectum, and sending the sample to the laboratory for culture. Women who are screened positive for GBS will be given antibiotics during labour to reduce the chance of passing the bacterium to the baby.