When to offer of antenatal testing for Group Strep B GBS is appropriate?
If a woman carried GBS in a previous pregnancy and the baby did not develop GBS disease, an Enriched Culture Medium (ECM) swab test for GBS carriage at 35-37 weeks (or earlier if preterm delivery is anticipated) should be offered.
The ECM test is not the same as a standard swab for a vaginal discharge. Swabs should be taken both from the low vagina and rectum, with samples cultured using enriched culture media and processed ASAP. You should specifically state ‘test for GBS’ on the request form.
If positive, the woman should be offered antibiotics in labour. If negative, she can be reassured that the risk of early onset neonatal GBS disease is very low (about 1 in 5,000). If she declines the test, she should be offered antibiotics in labour.