Decline in Perinatal Group B Strep Infections
September 1, 1997 3 minutes read
Decline in Perinatal Group B Strep Infections
Abstract & Commentary
Synopsis: The incidence of perinatal group B strep infections declined in some areas during 1993-1995. The reduction in cases of early-onset disease may be attributed to programs of prenatal screening for group B strep and intrapartum treatment of patients whose infants are at risk for group B strep infection.
Source: MMWR Morb Mortal Wkly Rep 1997;46: 473-478.
To determine the incidence of group b streptococcal (GBS) disease, the Centers for Disease Control and Prevention (CDC) surveyed metropolitan areas in San Francisco, Tennessee, Atlanta, and the entire state of Maryland during 1993-1995. The incidence of neonatal GBS disease was determined by the surveillance of hospital laboratories and by calculating the number of liveborn infants for 1993-1995 from state health department data or CDC’s National Center for Health Statistics. Invasive GBS disease was defined as isolation of GBS from a normally sterile site such as blood or cerebral spinal fluid. Cases were categorized as early-onset (less than 7 days of life) and late-onset (age 7-90 days).
The investigation revealed a statistically significant 43% fall in the incidence of early-onset GBS disease in Maryland and San Francisco from 1.4/1000 in 1993 to 0.8/1000 in 1995. The incidence rate of early onset GBS disease did not decline in Tennessee or Atlanta. During the three years of the study, 1071 cases of invasive GBS disease were reported among newborns less than 90 days of age, and 822 cases (77%) were categorized as early onset disease. Nearly 90% of the affected infants had bacteremia. The case-fatality rate for early onset disease was 4.5%. The case-fatality rate was higher for preterm infants (16%) than for term infants (2%).
The authors conclude that the incidence of perinatal GBS disease declined in some areas during 1993-1995. The reduction in cases of early onset disease may be attributed to programs of prenatal screening for GBS and intrapartum treatment of patients whose infants are at risk for GBS infection.
COMMENT BY STEVEN G. GABBE, MD
GBS is the single most important cause of neonatal mortality due to infection in the United States. In 1990, GBS infections resulted in 310 deaths among infants in this country, and most of these were early-onset infections. The incidence of early-onset GBS disease changed little during 1991-1993. For that reason, the present report from the CDC is an important one. This survey of a population of 12.5 million people with 190,000 live born infants each year revealed a statistically significant decline in the incidence of early-onset GBS disease in Maryland and San Francisco. Why the same pattern of change was not observed in Tennessee or Atlanta is unclear, but some data are presented suggesting that application of the latest methods for patient screening and culturing for GBS had not yet been adopted in these areas.
In June 1996, the American College of Obstetricians and Gynecologists Committee on Obstetric Practice supported recommendations from the CDC for the prevention of early onset GBS infection. Two strategies were proposed. The obstetrician can perform a screening culture at 35-37 weeks’ gestation and offer intrapartum antimicrobial prophylaxis to all carriers identified as well as women who deliver preterm before the availability of culture results. Both penicillin and ampicillin are recommended for prophylaxis.
The second strategy calls for the use of intrapartum antimicrobial treatment of women with identified risk factors including intrapartum fever, rupture of the membranes for more than 18 hours, premature labor or preterm premature rupture of the membranes, or previous birth of a child with GBS disease. The latter policy has resulted in an 80% reduction in early onset GBS disease over the past three years at the University of Washington Medical Center.
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