Group B Strep in Pregnancy

At 30 weeks I was diagnosed with strep B. Can you tell me more about this condition?

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Peg Plumbo CNM

Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more

Group B strep (GBS) is the most common cause of life-threatening infections in newborns. GBS has also been implicated in preterm labor and premature rupture of the membranes.

The incidence of GBS is about 20 percent (range of 12 to 35 percent), for the general population. In one study of over 7,000 women, Caucasians had a rate of 13.7 percent; African-Americans, 21.2 percent; and Hispanics, 20.9 percent.

GBS is present in the environment, but some people are more susceptible to it. Pregnancy lowers immune response and may make the circumstances right for colonization.

The Centers for Disease Control and Prevention recommend universal screening of all pregnant women and treatment of those with GBS. All women between 35 to 37 weeks of pregnancy should be routinely screened for GBS colonization by collecting a swab from the vagina and rectum.

Higher incidences of GBS occur in women with these clinical signs:
-- Redness, swelling and scaling of the external genitalia
-- Vaginal discharge and a vaginal pH of 5.0

Women at risk include:
-- Older women, women of lower parity and
-- Women who had yeast infections in the past 12 months
-- Women who had multiple partners in the past 12 months

Risk factors include:
-- Labor or rupture of membranes before 37 weeks pregnancy
-- Rupture of membranes 18 hours or more before giving birth
-- GBS carriage late in pregnancy
-- Fever in the mom during labor
-- Urinary tract infection due to GBS
-- Previous baby with GBS disease

High-risk women, and those with positive cultures, are treated with IV antibiotics in labor.

Why not treat all women with GBS during pregnancy? If we treat everybody with GBS early in pregnancy, we expose the majority of women to needless antibiotic use, because chances are they will need it again later. Apparently, it is relatively easy to eradicate this organism from the urinary tract, but very difficult to rid it from the GI tract, especially the rectum. This is why recolonization can take place, even without a repeat contact with a carrier.

One study showed that about 13 percent of the population had positive cultures in labor, despite negative cultures throughout pregnancy, and about 50 percent lost carrier status at some point in pregnancy. Cultures taken closer to term are more predictive of GBS status in labor than cultures taken earlier.

Current Recommendations
All women identified as GBS carriers, by culture, should be offered intravenous antibiotics during labor and delivery -- even if no other risk factors are present.

If a woman has not had a GBS cultures prior to the onset of labor or rupture of athe membranes, prophylactic intravenous antibiotics should be administered if one of the following is present:
-- Pregnancy of less than 37 weeks
-- The membranes have been ruptured 18 hours or longer
-- A temperature of 100.4 degrees F (38 degrees C) or greater

Women with the following conditions should receive intravenous antibiotics during labor, whether or not they tested postived for GBS:
-- Previous baby with GBS disease
-- Urinary tract infection due to GBS

If a cesarean is done, antibiotics would still be given before and during the birth process and would be continued for the mother postpartum to prevent infection of the uterus.

With treatment in labor, as well as treatment of high-risk babies after birth, the majority of babies never get infected.

In one study, only 1.1 percent of the babies developed early onset infection if the mothers were given penicillin during labor, compared with nine percent in the no-treatment group.

What treatment can you expect? Routine use of antibiotics for infants born to mothers who have received intravenous antibiotics during labor is not recommended. However, antibiotic use is appropriate for infants with suspected sepsis.

For infants without symptoms whose mothers have received intravenous antibiotics during labor, those with gestations of less than 35 weeks should have a limited diagnostic evaluation -- complete blood count and differential, and blood culture -- and be observed in the hospital for at least 48 hours (no early discharge). If during hospital observation signs of systemic infection develop, a complete diagnostic evaluation should be performed, and antibiotic therapy should be initiated.

In asymptomatic infants with a gestational age of 35 weeks or longer, the duration of intravenous antibiotic use before delivery determines subsequent management. If two or more doses of antibiotics were given before delivery, no laboratory evaluation or antibiotic therapy is recommended. These infants should be observed in the hospital for at least 48 hours (no early discharge). If only one dose of maternal antibiotics was given before delivery, infants should have a limited evaluation -- complete blood count and differential, and blood culture -- and at least 48 hours of observation before hospital discharge.

Approximately 80 percent of GBS cases occur within the first eight days of life, and these are defined as early-onset infection. In the remaining cases, the disease becomes apparent within the first month and these are defined as late-onset. About 300 to 350 babies die each year in the U.S. as a direct result of group B beta strep infection. Babies born by cesarean would be treated in the same way as for vaginal birth. We now know that babies can be colonized despite no labor and despite intact membranes.

There is a support group that might be a good resource for you: Group B Strep Association.

Source: American Academy of Pediatrics

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