All pregnant women shouldbe screened at 35 to 37 weeks of gestation for group B streptococcal(GBS) colonization, and identified carriers should be givenintravenous penicillin as soon as possible after hospital admissionthrough delivery, according to revised guidelines from the U.S.Centers for Disease Control and Prevention (CDC) (MMWR. 2002;51(RR11):1-22[Medline]). The recommendations also are available at www.cdc.gov/groupbstrep.
Group B streptococcal pneumonia in aneonate.
Previous CDC guidelines for GBS prevention approvedin 1996 by the American College of Obstetricians and Gynecologists(ACOG) and the Academy allowed either an intrapartum risk factor-basedor an antenatal GBS screening culture method to select womenfor intrapartum antibiotic prophylaxis (IAP). However, recentdata directly comparing the two methods in 5,144 births demonstratedthat culture screening was over 50% more effective than a risk-basedstrategy in preventing early-onset GBS disease in neonates (
SchragS, et al. N Engl J Med. 2002;347:233-239[Abstract/Free Full Text]). These data promptedreconsideration of prior guidelines.
Impact of prior guidelines
Since the publication of the first AAP guidelines in 1992, therehas been a 70% reduction in the number of early-onset GBS diseasecases, a decline attributed to the efficacy of maternal IAPand widespread implementation of 1996 "consensus" recommendationsfrom CDC, ACOG and the Academy.
Despite this substantial decline, cases still occur, and severalobservational studies have indicated that many cases have beenborn to women with no defined risk factors for infant GBS disease(preterm labor at less than 37 weeks, rupture of membranes formore than 18 hours, intrapartum fever of 100.4 degrees F orhigher, GBS bacteriuria, prior delivery of an infant with GBSdisease).
The new CDC data provide the first direct comparison of thetwo methods for identifying women for IAP. Culture-based screeningnot only was more effective but also was more often associatedwith administration of intravenous penicillin more than fourhours before delivery. Hopefully, adoption of universal GBSculture screening will result in an even greater reduction inthe incidence of early-onset GBS disease.
Changes in the 1996 recommendations
Many of the 2002 CDC recommendations outlined in Preventionof Perinatal GBS Disease are the same as the 1996 guidelinesfrom CDC, ACOG and the Academy (see Figure 1).
Penicillin remains the IAP drug of choice.
Women with unknownGBS status at delivery are managed by therisk-based approach.
GBS culture-negative women do not need IAP.
Women with GBSbacteriuria during the current pregnancy or whopreviously havegiven birth to an infant with invasive GBS diseaseshould receiveIAP.
GBS-positive women without bacteriuria should not receiveantenatalantibiotic therapy for GBS colonization.
In addition to culture screening as the only acceptable preventionmethod, the new recommendations:
update regimens for penicillin-allergic women (cefazolin issuggested for patients at low risk for anaphylaxis),
providedetailed instructions for collection of lower vaginaland rectalswabs, GBS culture processing and susceptibilitytesting ofisolates,
present an algorithm for management of obstetricalpatientswith threatened preterm delivery,
recommend againstGBS prophylaxis in women undergoing cesareandeliveries withoutpreceding labor or membrane rupture, and
reiterate that maternalIAP is an interim prevention strategyuntil GBS vaccines achievelicensure.
Management of newborns
Representatives from the AAP Committees on Infectious Diseasesand Fetus and Newborn assisted in preparation of the CDC’srecommendations regarding management of newborns born to womenreceiving IAP for GBS prevention. Variations in the managementalgorithm (see Figure 2) that incorporate individual circumstancesor institutional preferences may be appropriate.
Based on information since the publication of the 1997 AAP guidelines,an approach for empiric management of the neonate born to amother with suspected chorioamnionitis is provided.
The new recommendations also contain the following changes:
If a woman is suspected of having chorioamnionitis, her newbornshould have a full diagnostic evaluation and receive empiricbroad spectrum therapy (e.g., ampicillin and gentamicin) pendingculture results, regardless of the infant’s clinical conditionat birth or gestational age.
When a neonate has clinical signsof sepsis, a full diagnosticevaluation should include a lumbarpuncture, if feasible. Ifthe lumbar puncture has been deferredand the therapy is continuedmore than 48 hours because of suspectedinfection, cerebrospinalfluid should be obtained for routinestudies and culture.
In addition to penicillin or ampicillin,IAP with cefazolinat least four hours before delivery is consideredadequate,because cefazolin achieves bactericidal con- centrationsagainstGBS in amniotic fluid three hours after an IAP dose.The effectivenessof other antimicrobial agents in preventingGBS is unknown.
Hospital discharge as early as 24 hours afterbirth may be reasonableunder certain circumstances, specificallywhen the infant isborn after four or more hours of maternalIAP, is 38 weeks’gestation or more, appears healthy,and meets all dischargecriteria, including care by an individualable to comply fullywith instructions for home observation.
Dr. Baker is a member of the AAP Committee on Infectious Diseases.
