Group b strep positive first pregnancy negative second

A new study by researchers at The University of Texas Medical School at Houston could help experts better decide whether to continue the current practice of retesting women during their second pregnancies for a common bacterial infection if they had tested positive for the infection previously.

Group B Streptococcus, or GBS, is a type of bacterial infection that is harmless to carriers but in some cases can be deadly to an infant passing through the mother's birth canal. It is normally found in the vagina and/or lower intestine of 10 to 30 percent of all adult women. GBS is not a sexually transmitted disease. Those women who test positive for GBS are considered "colonized."

Published in the Aug. 1, issue of Obstetrics and Gynecology, the two-year study included more than 5,000 women who delivered their babies between 2003 and 2004 in the greater Houston area.

"Of those women, we were able to follow 418 women who gave birth vaginally, had a second child or more, were tested for GBS during their first and second pregnancies, and were not excluded from the study due to various factors. We found that of the 418, the risk of testing positive for GBS during a second pregnancy was 53 percent," said lead author Mark A. Turrentine, M.D., clinical assistant professor of obstetrics and gynecology at the UT Medical School at Houston.

According to Turrentine, research is ongoing to determine why some women are colonized and others are not. There also will need to be further studies conducted on how to use the information from this study.

Current guidelines by the Centers for Disease Control and Prevention (CDC) and the American College of Obstetricians and Gynecologists (ACOG) state that since colonization varies from pregnancy to pregnancy, women should be screened with each pregnancy.

"Our study did not tackle this issue, but the results could help experts decide whether it is cost effective to keep testing women in subsequent pregnancies if their risk of testing positive remains so high," said Turrentine.

Although GBS is not harmful to the mother, it can be deadly to an infant passing through the mother's birth canal. Signs and symptoms usually happen within hours of birth. They can include: difficulty breathing; heart, blood pressure, kidney and gastrointestinal problems; and sepsis, pneumonia or meningitis.

Some of the symptoms that increase a woman's risk of passing GBS to her baby include: labor before 37 weeks, rupture of her amniotic membrane 18 hours or more before delivery, fever during labor, a urinary tract infection as a result of GBS during pregnancy and a previous baby with GBS disease.

The CDC recommends routine screening for GBS for all pregnant women. The screening is given between the 35th and 37th week of pregnancy.

"The test involves a swab of the vaginal-rectal area. If a woman tests positive, and is therefore considered colonized, she will most likely be treated with intravenous (IV) antibiotic therapy during labor. The antibiotics will help protect the infant," said co-author Mildred M. Ramirez, M.D., associate professor in the Department of Obstetrics, Gynecology and Reproductive Sciences at the UT Medical School at Houston.

According to the CDC, one of every 100 to 200 babies whose mothers carry GBS will, without antibiotics, develop signs and symptoms of GBS disease.

If a woman's GBS status is unknown at the time of delivery, the CDC, ACOG and American Academy of Pediatrics recommend the women be given IV antibiotics during labor. The recommended regimen is intravenous penicillin.

GBS Infection in Newborn Babies

Most of the time, GBS is harmless. However, GBS can be passed to a newborn during birth.

Most babies who come in contact with GBS during birth will not become sick. But the few babies who do become ill can have severe problems.

After your baby is born, GBS can lead to infections in:

• The blood (sepsis)
• The lungs (pneumonia)
• The brain (meningitis)

Most babies who get GBS will start having problems during their first week of life. Some babies will not get sick until later. Symptoms can take as long as 3 months to appear.

The infections caused by GBS are serious and can be fatal. Yet prompt treatment usually leads to complete recovery.

Preventing GBS Infections in Babies

Women who carry GBS often don't know it. You are more likely to pass the GBS bacteria to your baby if:

• You go into labor before week 37.
• Your water breaks before week 37.
• It has been 18 or more hours since your water broke, but you haven't had your baby yet.
• You have a fever of 100.4°F (38°C)or more during labor.
• You have had a baby with GBS during another pregnancy.
• You have had urinary tract infections that were caused by GBS.

When you are 35 to 37 weeks pregnant, your doctor may do a test for GBS. The doctor will take a culture by swabbing the outer part of your vagina and rectum. The swab will be tested for GBS. Results are often ready in a few days.

Some doctors do not test for GBS. Instead, they will treat any woman who is at risk for having their baby be affected by GBS.

Treating and Preventing GBS Infections in Pregnant Women

There is no vaccine to protect women and babies from GBS.

If a test shows that you carry GBS, your doctor will give you antibiotics through an IV during your labor. Even if you are not tested for GBS but have risk factors, your doctor will give you the same treatment.

There is no way to avoid getting GBS.

• The bacteria are widespread. People who carry GBS often have no symptoms. GBS can come and go.

• Testing positive for GBS does not mean you will have it forever. But you will still be considered a carrier for the rest of your life.

Note: Strep throat is caused by a different bacterium. If you have had strep throat, or got it while you were pregnant, it does not mean that you have GBS.

References

Duff WP. Maternal and perinatal infection in pregnancy: bacterial. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 58.

Esper F. Postnatal bacterial infections. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 48.

Pannaraj PS, Baker CJ. Group B streptococcal infections. In: Cherry J, Harrison GJ, Kaplan SL, Steinbach WJ, Hotez PJ, eds. Feigin and Cherry's Textbook of Pediatric Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 83.

Verani JR, McGee L, Schrag SJ; Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention (CDC). Prevention of perinatal group B streptococcal disease--revised guidelines from CDC, 2010. MMWR Recomm Rep. 2010;59(RR-10):1-36. PMID: 21088663 pubmed.ncbi.nlm.nih.gov/21088663/.

Version Info

Last reviewed on: 4/19/2022

Reviewed by: John D. Jacobson, MD, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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