Group B strep testing: Understanding Local Screening Practices

Group B streptococcus, often shortened to GBS or group B strep, is a common bacterium that can live in the vagina or bowel without causing symptoms. Carrying it does not mean you have a sexually transmitted infection. Most babies are well, but GBS can occasionally cause serious newborn infection.

Check the local screening approach

Routine testing differs between countries. The NHS does not routinely offer GBS screening to everyone in pregnancy. GBS may instead be found on a urine sample or swab taken for another reason.

In the United States, routine screening includes a vaginal and rectal swab late in pregnancy, usually during week 36 or 37. Ask your maternity team which policy applies where you will give birth and whether your history changes the plan.

Keep the test’s name and date with your prenatal appointment schedule. A friend being offered a different test overseas does not tell you what your own service has arranged.

Know what a positive result changes

A positive swab generally leads to an offer of antibiotics through a vein during labour to reduce the risk of early newborn infection. A previous baby affected by GBS is also important information for the team.

A urinary infection caused by GBS needs treatment during pregnancy as well as a discussion about antibiotics in labour. Do not wait until birth to discuss a urine result. Our pregnancy urine testing guide explains why different urine tests answer different questions.

If you carry GBS and have a planned caesarean before labour starts and before your waters break, antibiotics specifically for GBS prevention are generally unnecessary. Routine antibiotics for the operation serve a different purpose. If labour or leaking waters starts first, contact maternity care promptly for an updated plan.

Put the birth plan in writing

Tell the team about antibiotic allergies and describe the reaction you experienced. Confirm when to call if labour starts, what to do if your waters break and where the result is recorded. If you move hospitals, check that the receiving team can see the information.

Ask what observation your baby may need after birth. Antibiotics in labour reduce early infection risk but do not prevent every case or protect against all later infections.

Seek emergency help if your newborn has trouble breathing, becomes floppy or unresponsive, has an unusual temperature or feeds poorly with signs of illness. A negative GBS screening result or antibiotics during labour should never delay assessment of an unwell baby.