When to screen pregnant women for GBS

In order to reduce the chances that the Group B Strep bacteria will be transferred from a colonized pregnant woman to her newborn child during labor and delivery, doctors generally agree that there is a need for routine screening for the bacteria during pregnancies where there is no other evidence that the mother is carrying the bacteria.  The question is – when is the best time to conduct screening testing?  Since Group B Strep can be present at certain times of the pregnancy and absent at other times, the consensus is that testing is most appropriately done between the 35th and 37th week of the pregnancy.  Evidence of the bacteria at this point in the pregnancy is considered to be a relatively reliable predictor that it will be present when the woman goes into labor and delivers the baby.  Thus, women who test positive are then given intravenous antibiotics during labor.