Pregnancy

What You Need To Know About Strep B and Pregnancy

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Understanding the risks of having Strep B during delivering.


“You’ve tested positive for Group B strep,” my obstetrician told me over the phone. I considered my first pregnancy to be mostly free of the usual problems and complaints that plague other moms-to-be. Having passed all of the routine pregnancy tests with flying colors, nothing prepared me for testing positive for Group B strep. I was floored by the news, utterly unaware of what this diagnosis was or how it could affect my unborn baby and myself.

What is Group B strep?
Group B streptococcus (GBS) is a natural bacterium found in the vagina, bowel, bladder, rectum and throat. According to the National Organization for Rare Disorders (NORD), the streptococcus bacteria reproduce and colonize in the mucous membranes of these body parts. GBS can be transmitted through touch, air or sexual contact. About one in four pregnant women are considered carriers of GBS but may show few symptoms or none at all.

Are You at Risk?
Group B streptococcus can be detected during pregnancy through a routine swab of the vagina and/or rectum for a culture test. The Centers for Disease Control and Prevention (CDC) state that this test should be conducted when a women is between 35 to 37 weeks pregnant. There has been some debate about risk-based versus culture-based screening.

According to Dale Mitchell, MD, chair of the department of obstetrics and gynecology at the Scripps Clinic Medical Group in San Diego, the conclusion was to, “screen all pregnant women with a culture-based screening. This led to fewer newborns being born with GBS infections. It was also found that screening at 35 to 37 weeks was more predictive of status at the time of delivery and also resulted in fewer neonatal infections.”

When a culture test is returned as positive, the result is that the pregnant woman is a carrier for GBS—not that she or her baby will become ill.  With some pregnant women, GBS infection may cause endometritis, womb infections and unfortunately, stillbirths, if GBS is left undiagnosed.

What Happens during Labor and Delivery?
A GBS infection becomes important during labor and delivery when women are administered a course of IV antibiotics such as penicillin or ampicillin every four hours. Pregnant women who have been diagnosed as GBS positive carriers should not be given oral antibiotics before labor because any treatment at this time will not prevent their babies from possible exposure to this infection. According to CDC guidelines, the only exception to this rule is when GBS is identified in urine during pregnancy. GBS found in the urine of expectant mothers should be treated at the time of discovery.

What Will Happen if I Go Into Labor Before Being Tested?
There is an inherent risk involved in the testing time frame. It was been widely researched and reported that cultures collected before week 35 to week 37 do not accurately predict whether a woman will have GBS at the time of delivery.

“Twenty percent of women carry GBS at any given time and carriage of GBS is intermittent,” explains Coleen McNally, MD, ABOG, chief medical officer at Sharp Mary Birch Hospital for Women & Newborns. “Testing is done at 35 to 37 weeks because it more accurately reflects GBS carriage status at delivery versus screening earlier.”

What should happen if a woman goes into labor before the 35th week of pregnancy and hasn’t been tested for GBS? Both the American College of Obstetricians and Gynecologists (ACOG) and the CDC recommend that a mom-to-be is administered IV antibiotics at the time of labor. Dr. Mitchell agrees, adding that the patient is always, “presumed to be a carrier. Culture is taken and antibiotics are continued until delivery and/or the culture is available.”

Early-Onset and Late-Onset GBS in Newborns
One out of every 100 to 200 babies born to women who carry GBS develop signs and symptoms of the infection. Generally, babies are exposed to the GBS bacterium during labor and delivery. However, there are several other ways that they can come in contact with it when the mother’s water breaks, when the bacteria travel up from the mother’s vagina into the uterus or swallowing/inhaling the bacteria while passing through the birth canal.

Newborns that become infected with GBS are classified as having one of two stages:  early-onset or late-onset. Infants infected with the bacterium either at birth or by their seventh day of life are diagnosed with early onset GBS, which can lead to inflammation of the baby’s lungs, spinal cord or brain; meningitis or sepsis. It is also a frequent cause of newborn pneumonia.

Infants who appear to be born healthy but develop symptoms of GBS from one week to several months after birth are diagnosed with late-onset GBS. This is a rare condition, since only about half of late-onset GBS disease comes from a mother who is a GBS carrier. According to Carol J. Baker, MD, professor of Molecular Virology & Microbiology at the Baylor College of Medicine, these babies can pick up GBS from a variety of different sources. “This is another possibility within the ‘community spread’ syndrome. Both mom and baby come home from the hospital together and the mother may transmit it to her baby through poor hygiene (not washing hands) or dad might have it and transmit it to the baby through contact. Also, the baby could have come in contact with it through the hospital environment.” Meningitis and pneumonia are considered symptoms of late-onset infection, which can bring long-term problems associated with the infant’s nerve system. However, if the infection in these babies is promptly treated, specialists will agree that there is usually no long-term damage.

The medical community is working to create a vaccination that protects women and their babies from the dangers of GBS.

“Several trials are underway, but to date, the vaccines have not resulted in a strong enough antibody response to eliminate GBS disease,” says Mitchell. Until this vaccination becomes available, it cannot be stressed enough for moms-to-be to make sure they are tested for this bacterium during their 35th to 37th week of pregnancy. If your obstetrician/primary care physician doesn’t mention this, bring it up during your routine check-ups. Knowing your culture result before you go into labor can help save your baby’s life.


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Jennifer Lacey is a freelance journalist specializing in pregnancy/parenting. Her work is frequently featured in numerous national and regional publications.

Published: December 2013