Group B Strep During Pregnancy

You find out you're a carrier of Group B Streptococcus. Your doctor says it's common, but you're still wondering: Is it dangerous for the baby? What happens during labor?

Group B Streptococcus (GBS) is a bacterium that occurs naturally in the gut and genital tract of many women. Being a carrier does not mean you are sick. But during labor, the bacterium can be passed to the baby and, in rare cases, cause a serious infection.

Here you'll find an overview of what GBS is, how it is managed, and what you need to know before giving birth.

What Is Group B Streptococcus?

GBS (Group B Streptococcus, or Streptococcus agalactiae) is a common bacterium found in the gut of most people. In approximately 20–30% of women, the bacterium is also present in the vagina.

Carrying GBS is entirely normal and causes no symptoms. You won't know it's there. It is not a sexually transmitted infection, and it does not mean your hygiene is poor.

The bacterium can come and go. You may test positive in one pregnancy and negative in the next, or the other way around.

Why Is GBS Relevant During Labor?

During birth, the baby may be exposed to the bacterium in the birth canal. For most babies this happens without problems — they are colonized but do not become ill.

In rare cases (approximately 1–2 per 1,000 births to GBS-positive mothers) the bacterium can cause a serious infection in the newborn. This is called early-onset neonatal GBS disease.

Possible Complications for the Baby

• Sepsis (bloodstream infection) — the most common complication
• Pneumonia — often in combination with sepsis
• Meningitis (brain membrane inflammation) — rare, but serious

Early-onset neonatal GBS disease typically occurs within the first 24–48 hours after birth. Symptoms include temperature changes, poor feeding, rapid breathing, and general lethargy.

Screening Guidelines

In the United States, ACOG (American College of Obstetricians and Gynecologists) and the AAP recommend routine GBS screening for all pregnant women at 36–37 weeks of pregnancy.

Other countries use a risk-based approach, meaning your doctor or midwife assesses whether risk factors suggest that GBS prophylaxis should be given during labor, rather than testing everyone routinely.

When Is Testing Done?

GBS testing (a swab from the vagina and rectum) is recommended:

• Routine screening at 36–37 weeks — standard in the US per ACOG guidelines
• Previous baby with GBS disease — automatic indication for prophylaxis
• GBS in urine during this pregnancy — indicates high bacterial load
• Preterm labor (before 37 weeks) — testing may be done at admission
• Premature rupture of membranes — especially if more than 18 hours before birth

If you are tested, the swab is taken from the lower vagina and rectum. Results typically take a few days.

The Rationale for Routine Screening

ACOG's guidelines are based on evidence that identifying GBS carriers before labor allows targeted antibiotic prophylaxis, significantly reducing neonatal GBS disease. A positive test at 36–37 weeks is a reliable predictor of carrier status at the time of delivery.

Risk Factors for GBS Transmission

The risk of the baby becoming infected increases with:

• Preterm birth (before 37 weeks)
• Rupture of membranes more than 18 hours before birth
• Fever in the mother during labor (over 100.4°F/38°C)
• Previous baby with GBS infection
• GBS bacteria in urine during this pregnancy

The more risk factors present, the more important preventive treatment becomes.

Treatment During Labor

Preventive treatment consists of intravenous antibiotics given to the mother during active labor. Penicillin is the first-line choice.

How Treatment Is Given

• Antibiotics are given intravenously (IV) when labor is underway
• First dose is given as early as possible after active labor begins
• The dose is repeated every four hours until the baby is born
• Optimal protection is achieved when the first dose is given at least 4 hours before birth

Treatment is effective and reduces the risk of early GBS disease in the baby by more than 80%.

What About Penicillin Allergy?

If you are allergic to penicillin, alternatives are available. Tell your doctor or midwife about the allergy well in advance — ideally at a prenatal visit. The alternative depends on the severity of the allergy.

What to Ask Your Doctor or Midwife

Good communication with your healthcare provider is key. Here are questions to ask:

• "Do I have any risk factors for GBS?" — Review your history and current findings
• "Should I be tested?" — Depends on risk factors and local guidelines
• "What happens if my water breaks early?" — Important to know the plan in advance
• "Does GBS affect my birth plan?" — For example, water birth and GBS
• "What will happen with the baby after birth?" — Observation routines

GBS and Your Birth Preferences

GBS prophylaxis requires IV access, but this does not mean you have to lie still in bed. You can still:

• Move freely between doses
• Use a birthing ball, warm water (shower), and other pain relief methods
• Have skin-to-skin contact with your baby immediately after birth
• Breastfeed as normal

Monitoring the Baby After Birth

After birth, the baby is observed for signs of GBS infection. The extent of observation depends on whether the mother received antibiotics and any risk factors present.

Signs staff look for:

• Temperature changes (too high or too low)
• Rapid or labored breathing
• Poor feeding
• Lethargy or irritability
• Changes in skin color

Most babies exposed to GBS remain completely healthy. If the baby shows signs of infection, antibiotic treatment is started immediately. Early treatment produces very good outcomes.

Cesarean Section and GBS

With a planned cesarean section where the membranes have not ruptured, the risk of GBS transmission is very low. The baby does not pass through the birth canal, and the bacterium has little opportunity to be transmitted.

GBS prophylaxis is therefore not usually necessary for a planned cesarean. However, if the membranes rupture before a cesarean, or if an emergency cesarean is needed after labor has begun, antibiotics are considered according to standard guidelines.

Late-Onset GBS Disease

In rare cases, GBS disease can occur from 7 days to 3 months after birth (late onset). This type is not prevented by antibiotics during labor.

Symptoms are the same as early-onset disease: fever, poor feeding, lethargy, irritability. Contact your doctor immediately if your newborn shows any of these signs.

Frequently Asked Questions

Can GBS be treated during pregnancy?

Antibiotics during pregnancy temporarily eliminate the bacterium, but it usually returns. Treatment is therefore given during labor itself, so the baby is protected when passing through the birth canal.

Is GBS dangerous for me as a pregnant woman?

No, GBS rarely causes illness in healthy adults. In very rare cases it can cause a urinary tract infection or an infection in the uterus after birth. Being a carrier itself is completely harmless.

Can I breastfeed if I have GBS?

Yes, absolutely. GBS is not transmitted through breast milk. Breastfeeding is recommended as normal and provides the baby with important antibodies.

Read More

• Prenatal check-ups: Your complete guide — what is checked at each visit
• Stages of labor: From contractions to birth — how labor progresses
• Pregnancy timeline — follow your pregnancy week by week

Sources

1. CDC — Group B Strep
2. ACOG — Group B Streptococcal Disease
3. AAP — Group B Streptococcus