Group B Strep in Pregnancy: What U.S. Families Should Know About Screening, Antibiotics, and New Vaccine Research

Bottom line: Group B strep (GBS) is a common bacterium that many adults carry without symptoms. During pregnancy, routine screening and timely antibiotics during labor have greatly reduced serious infections in newborns. Here’s what current U.S. guidance says, what signs parents should watch for, and what researchers are studying next.

What Is Group B Strep?

Group B Streptococcus (GBS) is a type of bacteria that can live in the digestive and genital tracts. According to the CDC, about 1 in 4 pregnant people in the United States carry GBS at any given time. Most have no symptoms and do not feel sick.

In adults, GBS is usually harmless. But during childbirth, the bacteria can pass from a pregnant person to their baby. In newborns, GBS can cause serious infections such as:

Sepsis (a bloodstream infection)
Pneumonia (lung infection)
Meningitis (infection of the lining around the brain and spinal cord)

Because of this risk, GBS screening and prevention are a routine part of prenatal care in the United States.

What Do Current U.S. Guidelines Recommend?

The CDC and the American College of Obstetricians and Gynecologists (ACOG) recommend universal screening for GBS between 36 and 37 weeks of pregnancy. This involves a simple swab of the vagina and rectum, usually done during a prenatal visit.

If the test is positive, the standard approach is intravenous (IV) antibiotics during labor. The goal is to reduce the amount of bacteria and lower the chance that the baby will be exposed during delivery.

According to CDC guidance, this strategy has reduced early-onset GBS disease (infection occurring in the first week of life) by more than 80% since the 1990s, when national prevention efforts began.

Who Should Receive Antibiotics During Labor?

Antibiotics during labor are recommended if:

The GBS screening test is positive.
GBS bacteria are found in urine at any point during pregnancy.
A previous baby had GBS disease.
GBS status is unknown and labor begins preterm, membranes have been ruptured for 18 hours or more, or a fever develops during labor.

Penicillin is typically the first-line antibiotic, according to ACOG. Alternatives are available for people with certain allergies.

What Symptoms Should Parents Watch for in Newborns?

Despite prevention efforts, a small number of newborns still develop GBS infections. Parents and caregivers should seek medical care right away if a newborn shows:

Fever or low body temperature
Difficulty feeding
Breathing problems
Extreme sleepiness or irritability
Unusual changes in skin color

Early treatment is critical. Newborns with suspected GBS infection are typically treated with IV antibiotics in the hospital.

Early-Onset vs. Late-Onset GBS

There are two main types of GBS disease in infants:

Early-onset disease (0–6 days of life), usually related to exposure during birth.
Late-onset disease (7 days to about 3 months), which may come from other sources and is not fully prevented by antibiotics during labor.

While early-onset disease has declined sharply with screening and antibiotics, late-onset disease has not decreased to the same degree. Researchers are continuing to study why and how to better prevent it.

What About a GBS Vaccine?

There is currently no approved GBS vaccine in the United States. However, vaccine development has been an active area of research, including clinical trials listed on ClinicalTrials.gov and studies supported by NIH and international partners.

Most vaccine candidates aim to protect pregnant people so they can pass protective antibodies to their babies before birth. In theory, this approach could help prevent both early- and late-onset disease.

It’s important to note that as of March 2026, no GBS vaccine has received FDA approval. Ongoing studies are evaluating safety, immune response, and effectiveness. As with any vaccine in pregnancy, large, carefully designed trials are required before recommendations can change.

Does GBS Affect the Pregnant Person?

Most pregnant people with GBS have no symptoms. In rare cases, GBS can cause urinary tract infections, infection of the amniotic fluid, or postpartum infections.

If GBS is found in the urine during pregnancy, it is usually treated at that time with oral antibiotics, and IV antibiotics are also recommended during labor.

Access, Equity, and Why Screening Matters

Routine GBS screening is standard prenatal care in the United States. However, access to consistent prenatal care can vary by insurance status, geography, and social factors.

Timely prenatal visits allow for screening, documentation of results, and planning for delivery. According to CDC data, racial and ethnic disparities persist in rates of certain maternal and infant health outcomes. Ensuring consistent screening and evidence-based care is one way to reduce preventable newborn infections.

What This Means for Families

GBS is common and usually harmless in adults.
Routine screening at 36–37 weeks of pregnancy is standard and important.
If you test positive, IV antibiotics during labor are highly effective at reducing early newborn infection.
Know the warning signs of infection in newborns and seek care promptly if they appear.
Vaccine research is ongoing, but no GBS vaccine is currently approved in the U.S.

If you are pregnant or planning a pregnancy, ask your clinician about GBS screening and how results will be documented in your birth plan.

Sources

Centers for Disease Control and Prevention (CDC) – Group B Strep (GBS)
American College of Obstetricians and Gynecologists (ACOG) – Prevention of Group B Streptococcal Early-Onset Disease in Newborns
ClinicalTrials.gov – Ongoing studies of maternal GBS vaccines

This article is for general informational purposes only and is not medical advice. Research findings can be early, limited, or subject to change as new evidence emerges. For personal guidance, diagnosis, or treatment, consult a licensed clinician. For current outbreak or public health guidance, follow your local health department, the CDC, or another relevant public health authority.