Testing positive for group B strep during pregnancy can be scary, but there's a simple treatment that can keep your baby safe. Check out our need-to-know guide.

By Dina Roth Port
pregnant belly
Credit: PeopleImages/Getty Images

When Allison Walters* of New York City found out she had tested positive for group B streptococcus (GBS)—a common bacteria that can be transmitted to a baby during delivery and can result in serious health issues for the newborn—during her second pregnancy, she started crying in her ob-gyn's office.

"As my doctor explained to me how incredibly important it was that I get treated with antibiotics before the baby was born, I knew this would be an added element of stress and worry," she recalls. "Knowing how dangerous it could be for the baby really scared me, and it also meant that I'd have to head to the hospital much earlier than I would have liked. I wanted to labor at home for as long as possible and have a natural birth, just like I did with my first child."

Hearing you have GBS during pregnancy can certainly be frightening. But knowing exactly what it is—and how it might affect you and your baby —can help keep both of you safe.

What is GBS?

Group B streptococcus is a common type of bacteria that is often found in the rectum or vagina of healthy women. Around 25 percent of women carry these bacteria, which are usually not harmful, though they might cause a urinary tract infection and, rarely, more serious infections. The real risk is that a woman can transmit it to her baby during labor and delivery—and that, in turn, can cause serious complications for the newborn, including pneumonia, meningitis, systemic infection, and sepsis (an infection in the blood).

Simply put, it can be fatal in infants. That's why the Centers for Disease Control and Prevention (CDC) recommends that all pregnant women get screened for GBS.

How does a woman get GBS?

Experts aren't sure why some women might carry GBS while others don't. "Some individuals are more likely to become colonized with GBS than others when their gastrointestinal tract is randomly exposed to the organism," says Lynn Simpson, M.D., chief of the division of maternal-fetal medicine at Columbia University Medical Center. "Colonization can be transient, intermittent, or persistent."

Adds Dana Stone, M.D., an ob-gyn in Oklahoma City and a spokesperson for the American Congress of Obstetricians and Gynecologists: "We carry many bacteria in our bodies, and GBS seems to be one of them for many people. Women can carry it during one pregnancy and not in another, so we check for it in each pregnancy."

What are the symptoms of GBS?

The majority of women with GBS have no symptoms, but those who have a heavy colonization may have symptoms similar to a bladder infection.

When is the Group B strep test taken, and what does it involve?

The Group B strep test is usually given during weeks 35 to 37. In this quick and painless test, your practitioner takes a swab of your vagina and rectum. The sample is sent to a lab for a culture to test for the presence of Group B strep.

Why is GBS screening done near at the end of pregnancy?

"Since GBS can be a normal gut flora and colonization can be intermittent or recurrent, it's optimal to screen late in pregnancy, when the culture results are likely to reflect the status at the time of delivery," says Dr. Simpson "Treating earlier has not been shown to be effective at decreasing early-onset GBS disease in infants and may result in the development of antibiotic resistance over time. Therefore, early treatment is not recommended."

In other words, since GBS can grow back very quickly, antibiotics can help only when given during labor.

What happens if you test positive for GBS?

If you test positive, ask your doctor what to expect. "All women who test positive for GBS during pregnancy (as well as those who have had a baby with a GBS infection in the past or those who had a GBS urinary tract infection during the pregnancy) should receive antibiotics—typically penicillin—during labor to prevent transmitting GBS to the baby," says Dr. Stone. "Women who have preterm labor and don't know their GBS status are also treated in case they carry GBS."

Stephanie Schrag, D. Phil., an epidemiologist at the CDC, agrees: "The best steps a mother can take to help protect her baby is to go to the hospital and get antibiotics for at least four hours before delivering, tell the labor and delivery staff at the hospital that she's a GBS carrier, and speak up if she's allergic to penicillin so another antibiotic can be given. Getting antibiotics intravenously throughout labor is the only proven strategy to protect a baby from getting GBS disease in the first week of life." If your water breaks, you should get to the hospital right away so your doctor can start the antibiotic treatment.

Will having GBS change your birth plan?

"Being a GBS carrier does not always mean a woman needs to change her birth plan," says Dr. Schrag. "Regular checkups should continue and she should talk with her doctor or midwife about a plan for labor so antibiotics can be given before delivering the baby."

If you're GBS-positive and scheduled for a C-section, specific GBS antibiotics aren't necessary, says Dr. Simpson. Instead, she says, you'll be given a broad-spectrum antibiotic prior to the skin incision to prevent maternal infections related to the surgery. But if your water breaks, or labor starts prior to a cesarean delivery, you'll need treatment for GBS just as women undergoing labor and a vaginal birth do.

What happens after delivery?

According to the CDC, if a woman who tests positive for GBS gets antibiotics during labor, her baby has only a 1 in 4,000 chance of getting GBS (compared to 1 in 200 chance if she doesn't get those antibiotics.) In other words, antibiotics during labor will prevent the vast majority of GBS. Your pediatrician will evaluate your baby, and if the baby shows any signs of infection, such as respiratory distress, apnea, difficulty feeding, or signs of sepsis such as fever and an abnormally rapid heart rate, he will receive antibiotics and supportive therapy to treat it.

The bottom line

"I know it can be scary to find out you have these bacteria and that your baby has a chance of getting sick," says Dr. Schrag. "But pregnant women should take comfort in knowing that GBS prevention guidelines have been in place for two decades in the United States and have proven effective in protecting babies."

As for Walters, when her water broke a week shy of her due date, she headed right to the hospital and got the antibiotics her baby needed. Yes, her birth plan changed slightly, but she says, "My son was born healthy—and ultimately that's all that mattered."

*Name has been changed