Should Group B Strep Test Be Carried Out On Subsequent Pregnancies?

Main Category: Pregnancy / Obstetrics
Also Included In: Pediatrics / Children's Health;  Infectious Diseases / Bacteria / Viruses;  Primary Care / General Practice
Article Date: 04 Aug 2008 - 0:00 PDT

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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.

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Melissa McDonald
University of Texas Health Science Center at Houston

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