What is the recommended test for detecting Group B Streptococcus (GBS)?

The recommended test for detecting Group B Streptococcus (GBS) is a vaginal-rectal swab performed at 35-37 weeks of gestation. This timing is critical because it allows for accurate identification of GBS colonization in pregnant women during the late stages of pregnancy, when the risk of transmission to the newborn during delivery is highest. The swab collects samples from both the vagina and rectum to ensure a thorough assessment since GBS can reside in either location.

Identifying GBS is essential because if a pregnant woman is found to be positive for GBS, she can receive prophylactic antibiotics during labor to reduce the risk of the newborn developing GBS infection, which can lead to serious complications. The recommendation for screening in late pregnancy provides the best balance of accurately identifying carriers and allowing time for appropriate interventions, if necessary.

The other testing options mentioned do not adequately identify the presence of GBS at the crucial time that can impact delivery and neonatal health. Early blood tests during the first trimester do not reflect current GBS status, urine tests at delivery may not be indicative of GBS colonization in the genital tract, and sonograms in the second trimester do not assess GBS status at all. Thus, the vaginal-rect