Group B strep positive: what it means for birth

What does a positive GBS result actually mean?

GBS (Group B strep) screening happens late in pregnancy. Your doctor takes a swab from your vagina and rectum, usually between 36 and 38 weeks. The lab checks the swab and records the result — positive or negative — in your chart. Your labor team uses this result when you go into labor.

A positive result doesn't change your due date or your ability to labor. In most cases, it doesn't change your birth plan either. It changes one thing: once labor starts, you'll be offered antibiotics through an IV to protect your baby during delivery. Everything else — pain relief, positions, who's in the room — is still up to you.

Why do antibiotics during labor matter so much?

Here are the numbers, plainly. Without antibiotics during labor, a GBS-positive mother passes the infection to her newborn about 1 to 2 times out of every 100 births. Other research puts it closer to 1 in 200 without treatment, versus about 1 in 4,000 with treatment. The exact numbers vary by study. But the pattern is the same: the risk without treatment is real, and antibiotics bring it down a lot.

Penicillin is the antibiotic doctors use most often to prevent early-onset GBS disease (illness that shows up in a newborn's first week). Timing matters as much as the medicine itself. The IV antibiotics work best when you get them at least four hours before delivery. Taking antibiotics before labor starts doesn't work the same way — you need them on board while labor is happening. One more thing to know: these antibiotics prevent early-onset disease, but not late-onset disease (illness that shows up later). That's why the newborn warning signs later in this article still matter, even after antibiotics during labor.

What if you're allergic to penicillin?

Tell your doctor about a penicillin allergy before your GBS test — not just before labor. That gives your team time to plan ahead. You may get a skin test to see how severe your allergy really is. Some reactions are mild enough that penicillin-family antibiotics are still safe. Others need a different antibiotic. Either way, other options exist. A penicillin allergy doesn't mean you go without protection during labor.

Do you need antibiotics if you're having a scheduled C-section?

If you have a scheduled C-section, you generally don't need GBS antibiotics during the surgery. This is true as long as labor hasn't started and your water hasn't broken by the time of surgery. The risk these antibiotics protect against comes from labor and passing through the birth canal — not from a planned surgery that happens before either one starts.

Still, get the GBS test done even with a C-section scheduled. Labor doesn't always wait for the calendar. If it starts, or your water breaks, before your surgery date, your team needs to already know your GBS status. That lets them decide quickly whether you need antibiotics.

What if there's no time for a fresh test?

Sometimes there isn't time for a fresh test, or waiting for a result isn't practical. In these cases, your doctor may give you antibiotics during labor without a current GBS result if any of these apply to you: you had a previous baby with GBS disease; you have GBS bacteria in your urine this pregnancy; you get a fever during labor and don't know your GBS status; you go into labor before 37 weeks and don't know your status; or it's been 18 hours or more since your water broke and you don't know your status.

None of these mean something has gone wrong. They're just situations where treating is the safer choice than waiting — because the antibiotics work well, and the window to give them can be short.

When should you call the doctor about your newborn?

Even with well-timed antibiotics, it helps to know what GBS disease can look like. Early-onset disease usually makes a baby sick within 12 to 48 hours after birth, though it can show up as late as day 7. It can cause meningitis (infection around the brain and spinal cord), pneumonia, or sepsis (a serious blood infection). Even with quick treatment, a small number of babies die from early-onset disease. That's exactly why spotting it fast matters.

Late-onset disease, and meningitis in particular, can be hard to spot in a newborn. There's no one obvious sign, the way there might be in an older child or adult. Call your baby's doctor right away if you notice any of these signs:

• Lack of energy or unusual sluggishness • Irritability that doesn't settle • Poor feeding • A high fever

You don't have to be sure something's wrong to call. These symptoms can be subtle in a newborn. Your baby's care team would rather check a false alarm than miss a real one.

Frequently asked questions

Sources

1. If a pregnant woman who tests positive for GBS does not receive antibiotics during labor, the chance of passing the infection to her newborn is about 1 to 2 babies out of 100; that chance is much lower when she receives antibiotic treatment. — ACOG
2. GBS screening is done via a vaginal-rectal swab culture performed between 36 and 38 weeks of pregnancy. — ACOG
3. Penicillin is the antibiotic most often given during labor to prevent early-onset GBS disease in newborns, and while intrapartum antibiotics can prevent early-onset GBS disease, they do not prevent late-onset disease. — ACOG
4. Women who are allergic to penicillin should tell their health care professional before GBS testing; they may have a skin test to determine allergy severity, and other antibiotics can be used if needed. — ACOG
5. A GBS-positive person planning a cesarean birth does not need GBS antibiotics during delivery if labor has not started and the amniotic sac has not ruptured, but she should still be tested because labor could begin before the scheduled cesarean. — ACOG
6. Doctors may give intrapartum antibiotics without a current GBS test result if the patient had a previous child with GBS disease, has GBS bacteria in her urine during this pregnancy, develops a fever in labor with unknown GBS status, goes into labor before 37 weeks with unknown status, or it has been 18 hours or more since her water broke with unknown status. — ACOG
7. With early-onset GBS disease, a baby typically becomes sick within 12 to 48 hours after birth (up to the first 7 days), and it can cause meningitis, pneumonia, or sepsis; a small number of babies die from early-onset disease even with immediate treatment. — ACOG
8. Parents should contact their baby's health care professional right away if the baby shows any signs of GBS disease, including lack of energy, irritability, poor feeding, or high fever, since late-onset disease symptoms and meningitis signs can be hard to spot in newborns. — ACOG
9. GBS intravenous antibiotics work best when given at least four hours before delivery, and treating GBS with antibiotics before labor begins is not effective. — Cleveland Clinic
10. With antibiotic treatment during labor, about 1 in 4,000 babies will get a GBS infection at birth, compared with about 1 in 200 if the mother does not receive antibiotics during labor. — Cleveland Clinic