A positive result is common and manageable
Group B streptococcus, or GBS, is a bacterium that can live in the vagina or rectum without causing symptoms. It is not a sign of poor hygiene and is not considered a sexually transmitted infection.
When testing happens
A vaginal and rectal swab is usually collected between 36 weeks, 0 days and 37 weeks, 6 days. Testing is repeated in each pregnancy because GBS can come and go.
A history of a baby with GBS disease or GBS found in urine during the current pregnancy may establish the need for labor antibiotics without another screening swab. ACOG: GBS prevention guidance
Treatment during labor
If indicated, antibiotics through an IV lower the risk of early newborn GBS infection. Penicillin is usually preferred. If you have an allergy, explain the reaction; the alternative depends on allergy severity and sometimes laboratory testing.
Antibiotics can cause stomach upset, rash, or rarely a serious allergic reaction. Your team balances those risks against preventing newborn infection. ACOG: GBS and pregnancy
Frequently asked questions
Should I take antibiotics now?
A positive swab alone usually calls for antibiotics during labor. A urinary infection may need treatment earlier too.
What if I have a planned cesarean?
GBS-specific antibiotics are generally unnecessary if surgery occurs before labor with intact membranes. Routine surgical antibiotics are still used.
When should I contact the hospital?
Tell your care team when labor starts or your water breaks. Do not delay necessary delivery just to complete an antibiotic interval.
Questions about your pregnancy? Contact Davie ObGyn in Davie, Florida, at 954-880-1010. New and established patients are welcome. This information supports your prenatal care and does not replace an individual medical assessment. For urgent symptoms, call your care team promptly; for an emergency, call 911. Do not use a routine online message for urgent symptoms.
Medically reviewed by Rahil Malik, MD, FACOG, board-certified obstetrician-gynecologist. Last reviewed: September 26, 2026. This page is general information and does not replace a visit with your doctor.