Group B Strep Screening Guidelines Sparing Newborns
WEDNESDAY June 17, 2009 -- Recommendations implemented in 2002 to screen all pregnant women for group B streptococcal disease have largely been successful, a new report shows.
Eighty-five percent of women in the United States are now being screened and, if positive, given appropriate treatment.
"This paper highlights an important public health success story," said study author Melissa K. Van Dyke, who was an epidemic intelligence service officer at the U.S. Centers for Disease Control and Prevention while conducting the study. "Recommendations for universal antenatal screening were rapidly adopted, and this corresponded with further declines in the incidence of early-onset GBS [group B strep] disease."
Van Dyke is now an epidemiologist at GlaxoSmithKline Biologicals in Rixensart, Belgium, although that company played no part in this study, which appears in the June 18 issue of the New England Journal of Medicine.
"These guidelines have been in place for many years now, and this study was asking whether these guidelines had actually had an impact on care, whether people's behavior had changed," added Dr. James M. Greenberg, director of neonatology at the Cincinnati Children's Hospital Medical Center. "And the answer is yes. Women are getting screened now in much higher percentages, they're getting treated and that has led to a reduction in disease in newborns."
GBS is bacteria that, according to the CDC, became the leading infectious cause of illness and death in newborns in the 1970s. GBS can cause sepsis, meningitis and pneumonia in infants, usually within the first week of life. If a pregnant woman is a carrier, the infection can be passed to her child during delivery.
The guidelines recommend that women get screened at 35 weeks to 37 weeks of pregnancy.
"If a mother is positive for group B strep, she is to get prophylactic antibiotics when she delivers," Greenberg explained. "It requires at least one and preferably two doses of penicillin more than four hours before delivery so it has time to have an effect."
The authors looked at birth records on 254 infants who had GBS disease and 7,437 infants who did not.
Between 1998-1999 and 2003-2004, screening rates jumped from just over 48 percent to 85 percent. This resulted in almost 32 percent of infants being exposed to antibiotics during delivery in the later timeframe, up from about 27 percent in the late 1990s.
Overall, there were 0.32 cases of GBS per 1,000 live births. Infants born premature had a higher incidence of GBS than infants born full-term (0.73 vs. 0.26 cases per 1,000 live births). Yet, most of the cases occurred in full-term infants.
Just over 13 percent of full-term GBS cases occurred in babies of mothers who had not been screened, whereas 61.4 percent occurred in babies of mothers who had actually tested negative for GBS at 35 to 37 weeks of pregnancy.
"Although the antenatal screening strategy has been very successful, we are also exploring ways that we can do even better, and one of them is understanding the issues around false-negatives," Van Dyke said. "While some false-negatives are expected because of the limits of the culture test, we were able to use our study design to show that we observed more false negatives than would be expected."
The term "false-negative" may be a bit of a misnomer, however, Greenberg pointed out.
"If screening is done at 35 weeks gestation, it is possible for a woman who is negative -- i.e., not a carrier -- to become a carrier by the time she delivers," Greenberg said. "Then there's a higher risk that she will pass on group B strep to her infant. Almost all the patients who we see now with group B strep are babies who are born to mothers who had 'false negative' kinds of tests."
One possibility might be to do additional testing later in the pregnancy, Greenberg said. Other instances in which guideline procedures aren't followed involve mothers who come in and deliver too quickly to benefit from antibiotics and women who are allergic to penicillin (although there are other treatment options for these women).
There is also a higher rate of group B strep in black infants than in others, the authors said, but the reasons for this are unclear.
Researchers are still working on a vaccine.
The U.S. Centers for Disease Control and Prevention has more on group B strep.
Posted: June 2009