Does testing positive for group B strep mean my baby will get sick?

No. Most babies born to GBS-positive mothers are perfectly healthy. The bacteria pass to about 50 to 70 percent of babies during birth, but only 1 to 2 percent of those exposed develop invasive disease, and antibiotics during labor lower that risk further.

Can I get rid of group B strep before delivery?

Taking antibiotics earlier in pregnancy doesn't work, because GBS often returns. That's why treatment is given during labor rather than weeks ahead. The exception is GBS found in your urine, which is treated when detected and also flags you for antibiotics in labor.

Is group B strep a sexually transmitted infection?

No. GBS is a normal bacteria that lives in the digestive and genital tracts of many healthy people. Carrying it is not a sign of poor hygiene, an STI, or anything you did wrong. Most carriers have no symptoms.

Do I still need antibiotics if I'm having a C-section?

If you have a planned cesarean before labor starts and before your water breaks, you typically don't need GBS antibiotics, because the baby isn't passing through the birth canal. Your provider will confirm what's right for your situation.

What if I'm allergic to penicillin?

There are safe alternatives. Depending on your allergy history, your provider may use cefazolin, clindamycin, or vancomycin instead. Tell your care team about any drug allergies before labor so the right antibiotic is ready.

Learning›Science of Skin

Strep B Bacteria in Pregnancy: What Group B Strep Means for You and Your Baby

June 5, 2026

Your provider mentioned a "strep B" test, or maybe a swab came back positive, and now you're worried you've done something to put your baby at risk. Take a breath. Group B strep is a common bacteria that lives in the bodies of many healthy people, and a positive result does not mean you're sick or that anything is wrong with your pregnancy.

Here's what matters most: group B strep in pregnancy is well understood, easy to screen for, and very manageable. A simple test near the end of pregnancy and antibiotics during labor protect the vast majority of babies. This guide explains what group B strep is, how it's tested, and exactly what happens if you test positive.

What is group B strep (GBS) in pregnancy?

Group B Streptococcus, often shortened to GBS or strep B, is a type of bacteria that naturally lives in the gut, vagina, and rectum of many healthy adults. It is not a sexually transmitted infection, and it is not the same bacteria that causes strep throat (that's group A strep). Most people who carry GBS have no symptoms at all and never know it.

Carrying GBS is called colonization, not infection. Roughly 15 to 35 percent of pregnant women are colonized with group B strep in the vagina and/or rectum at any given time, with several recent studies reporting rates around 22 to 26 percent. In other words, this is common. The concern in pregnancy is not the mother's health, but the small chance the bacteria can pass to the baby during a vaginal birth.

How and when is GBS tested in pregnancy?

The CDC and the American College of Obstetricians and Gynecologists (ACOG) recommend that every pregnant person be screened for group B strep in each pregnancy. The test is a simple swab of the vagina and rectum, and it is not painful. Your provider may let you do the swab yourself.

Screening is timed late in pregnancy because GBS colonization can come and go. Testing close to your due date gives the most accurate picture of whether the bacteria are present when you go into labor.

When: between 36 0/7 and 37 6/7 weeks of pregnancy
How: a single vaginal-rectal swab
Results: usually available within a few days
Exception: if GBS is found in your urine at any point in pregnancy, or you had a previous baby with GBS disease, you're treated as positive without needing the swab

What happens if I test positive for strep B?

A positive result simply means you're a GBS carrier. It does not require treatment during pregnancy, and oral antibiotics taken weeks before delivery won't help, because the bacteria can return. Instead, the protection comes during labor itself.

If you test positive, you'll be offered antibiotics through an IV once labor begins or your water breaks. Penicillin is the first-line choice and is considered safe in pregnancy; ampicillin, cefazolin, or other alternatives are used if you have a penicillin allergy. The goal is to have antibiotics on board for at least 4 hours before delivery, which in one cohort was about 78 percent effective at preventing early-onset GBS disease in the newborn. That said, your delivery should never be delayed just to reach the 4-hour mark.

Why GBS matters: the risk to the baby

When a mother carries GBS, the bacteria pass to the baby during birth in about 50 to 70 percent of cases. The vast majority of these babies are completely fine. Only about 1 to 2 percent of exposed newborns go on to develop early-onset invasive GBS disease, which can include serious infections like sepsis, pneumonia, or meningitis.

Overall, GBS disease affects roughly 1 to 2 babies per 1,000 births, but it remains the leading cause of early-onset neonatal sepsis in the United States. One important nuance: antibiotics during labor prevent early-onset disease (in the first week of life) but do not prevent late-onset GBS disease, which can appear from one week to three months after birth. That's why you should always report signs of illness in a newborn, even after a smooth delivery.

When to call your doctor

For you, contact your provider if you go into labor or your water breaks and you know you're GBS positive, so antibiotics can be started promptly. Also reach out if you have symptoms of a urinary tract infection, such as burning with urination, since GBS can cause UTIs in pregnancy.

For your baby, watch for warning signs in the days and weeks after birth and seek care right away if you notice any of the following. Trust your instincts; a newborn who seems off deserves a prompt evaluation.

Fever, or a temperature that's unusually low
Trouble breathing, grunting, or fast breathing
Poor feeding or refusing to feed
Unusual sleepiness, floppiness, or being hard to wake
Persistent irritability or a high-pitched cry

Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider before starting any new skincare treatment, especially if you have underlying health conditions, are pregnant, or are taking medications.