The CDC recommends screening for group B streptococcus at what point during pregnancy?

The correct answer is that the CDC recommends screening for group B streptococcus (GBS) at 35-37 weeks gestation. This timing is crucial because testing during this window allows for the identification of GBS status just before delivery, which is essential for implementing appropriate prophylaxis if the mother is found to be positive for GBS.

If a mother tests positive for GBS, she can receive intrapartum antibiotic prophylaxis during labor, which significantly reduces the risk of transmitting the bacteria to the newborn. Since GBS colonization can fluctuate during pregnancy, screening too early, such as at 20 weeks or at the first prenatal visit, may not provide an accurate reflection of a woman's GBS status at the time of labor. Testing at the onset of labor is not recommended, as it doesn't allow enough time to implement any necessary interventions effectively. Thus, the 35-37 weeks gestation timeframe is specifically chosen to maximize the chances of accurate results and effective management during delivery.