Group B Strep in Pregnancy
Antibiotics during labor can help protect your baby
Group B strep (GBS) is a common type of bacteria. It may live in the vagina, urine, or rectum, where stool leaves the body. Most people have no symptoms.
GBS is not a sexually transmitted infection. About 25% of pregnant women (1 in 4) have a positive GBS vaginal and rectal culture near delivery.
Who needs antibiotics during labor?
Antibiotics through a vein, called an IV, are recommended if:
- Your vaginal and rectal swab is positive. This means GBS was found.
- GBS was found in your urine during this pregnancy.
- A baby from an earlier pregnancy had GBS disease.
You do not need another GBS swab if GBS was found in your urine or a prior baby had GBS disease. If you only had a positive swab in an earlier pregnancy, you are usually tested again at 36 or 37 weeks.
If GBS was found in your urine
GBS in urine may be a bladder infection or a sign that a larger amount of GBS is present.
You may need antibiotic pills during pregnancy, especially if you have symptoms or a large amount is found. You will still need IV antibiotics during labor because GBS can return.
What happens during labor?
Penicillin is usually given through a small tube placed in a vein. This is called an IV. Tell the care team about any drug allergy. A different antibiotic can be used if needed.
Antibiotics work best when started at least 4 hours before birth, but they still help when given for less time. Needed care or birth should not be delayed just to reach 4 hours.
When should I go to the hospital?
Call your maternity unit or go to the hospital when:
- Labor starts.
- Your water breaks.
- Your care team tells you to come in.
Tell the hospital that you need GBS antibiotics.
What if I plan a C-section?
GBS antibiotics are not usually needed when a planned C-section happens before labor starts and before the water breaks. Antibiotics used for the surgery are still given.
If labor starts or the water breaks first, call the hospital and tell them about GBS.
Why protect the baby?
A small number of newborns get GBS disease, which is a serious infection caused by GBS. It can infect the blood, lungs, or the area around the brain. Antibiotics during labor greatly lower the risk during the baby's first week.
Educational use only. This handout does not replace care from your pregnancy doctor or your baby's doctor. Your care plan may be different. Updated September 2026.