Final answer:
GBS testing should be done during the 36th to 37th week of pregnancy to detect if group B strep is present and reduce the risk of neonatal meningitis by administering antibiotics during labor if necessary.
Step-by-step explanation:
Group B streptococcus (GBS) testing is an important part of prenatal care as S. agalactiae, or group B strep, is a leading cause of neonatal meningitis. It is recommended that pregnant women undergo GBS testing during the 36th to 37th week of pregnancy. This timing is crucial because it is close enough to the expected delivery date that the results will predict if the bacteria are likely to be present in the mother's body during labor. In the event that GBS is detected, intravenous antibiotics given to the mother during labor can significantly reduce the incidence of early onset neonatal meningitis, which is defined as occurring in infants up to 7 days old and happens when the infant becomes infected by the bacteria transferred during childbirth.