Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made. (Formerly, these situations were captured under a "C Recommendation".) This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade. For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.
Preventive Health Care, 2001 Update: Prevention of Early-onset Group B Streptococcal (GBS) Infection in the Newborn
Prepared by V. Shah, MD, MRCP, and A. Ohlsson, MD, MSc, FRCPC, FAAP, with the Canadian Task Force on Preventive Health Care
These recommendations were finalized by the Task Force in February 2001.
Contents
Objective(1) To perform a systematic review
of the evidence relating to the effectiveness of intrapartum
chemoprophylaxis administered to pregnant
women in preventing early onset group B streptococcal infection in the
newborn, and (2) to identify the best
preventive strategy.
Burden
of SufferingThere are two forms of group B streptococcal (GBS) disease in infants: early-onset disease (EOD) and late-onset disease (LOD). EOD is defined as isolation of GBS in an infant less than 7 days of age with signs and symptoms of systemic infection. It accounts for 80% to 85% of neonatal infections, has a higher mortality rate and is acquired through vertical transmission from colonized mothers (i.e., during passage through the birth canal or by an ascending route in utero through ruptured or intact membranes). The three most common clinical presentations include sepsis, pneumonia, and meningitis. LOD usually occurs in infants between one week and up to 3 months of age with meningitis being the most common clinical presentation (85% of cases). LOD is acquired either by vertical transmission (delayed infection after early colonization) or by horizontal transmission (due to cross infection in the hospital from healthcare workers or in the community). GBS also causes chorioamnionitis, endometritis, urinary tract infections, and puerperal wound infection.
Risk factors include: 1) preterm labor (< 37 weeks gestation), 2) prolonged rupture of membranes > 18 hours, 3) maternal fever > 38.0oC, 4) group B streptococcus bacteriuria during pregnancy, and 5) previous delivery of a newborn with group B streptococcus disease regardless of current group B streptococcus colonization.
The recent reduction of GBS in infants is attributed to prompt recognition and initiation of antibiotic therapy as well as improvements in neonatal intensive care. In Canada, the case-fatality rate was 9% for early-onset disease and 2% for late-onset disease.
OptionsThe
three management options available are a) universal screening of pregnant women
and selective intrapartum chemoprophylaxis to colonized women with risk factors,
b) universal screening of pregnant women for group B streptococcus colonization
and intrapartum chemoprophylaxis to all colonized women, and c) intrapartum
chemoprophylaxis based on risk factors only.
OutcomesThe
effectiveness of intrapartum chemoprophylaxis on (1) neonatal colonization and
(2) early onset group B streptococcal infection in the neonate.
EvidenceMEDLINE
(1966 – December 2000), EMBASE (1980 – December 2000) and the Cochrane
controlled trials register was searched for randomized controlled trials and
cohort studies evaluating the effectiveness of intrapartum chemoprophylaxis for
the prevention of early onset group B streptococcal infection in the newborn.
Cited references from retrieved articles, editorials indicating expert opinions,
personal files, standard neonatal and obstetric textbooks and included
references were reviewed. In the synthesis
of the evidence,
data from randomised trials and cohort studies were pooled separately.
Recommendations were graded as:
| Good evidence to support the recommendation that the condition be specifically considered in a PHE. | |
| Fair evidence to support the recommendation that the condition be specifically considered in a PHE. | |
| Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds. | |
| Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE. | |
| Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE. |
Quality of evidence was rated according to 5 levels:
| Evidence from at least 1 properly randomized controlled trial (RCT). | |
| Evidence from well-designed controlled trials without randomization. | |
| Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group. | |
| Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here. | |
| Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees. |
ValuesThe 8 member Task Force of experts in family medicine, geriatric medicine, paediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.
The two lead authors prepared a manuscript providing critical appraisal of the evidence. This included identification and critical appraisal of key studies, and ratings of the quality of this evidence using the Task Force's established methodological hierarchy. The resulting summary of proposed conclusions and recommendations for consideration was presented and deliberated upon in 1- to 2-day meetings from October 1998 to May 1999. Consensus was reached on final recommendations.
Benefits,
Harms, and CostsIntrapartum chemoprophylaxis (IPC) is effective in reducing both neonatal colonization (NC) and early-onset disease (EOD) in infants. The benefits, however, must be weighed against the number of women who need to be treated with IPC.
Potential harms include the emerging resistance to erythromycin and clindamycin among GBS strains, suggesting that this alternative therapy for women with penicillin allergy may need modification. Also of concern is the increased use of antibiotics in the perinatal period which may lead to an increased incidence of bacteria resistant to antibiotics used for perinatal infections.
The choice of a preventive strategy within a health care system depends on the incidence of the EOD, the patient characteristics, available clinical resources and maternal colonization rates. In Canada, cost-effectiveness information is lacking.
RecommendationsRecommendation
grade [A, B, C, D, E] and level of evidence [I, II-1, II-2, II-3, III]
are indicated after each recommendation. Citations in support of individual
recommendations are identified in the guideline text.
Collection
of antenatal cultures (swab from lower vagina and rectum) should occur at 35-37
weeks gestation. Swabs should be inoculated into selective broth medium,
followed by overnight incubation and then subcultured onto solid blood agar
medium. Currently
adequate intrapartum chemoprophylaxis consists of at least one dose of
intravenous penicillin (5 million units) given at least 4 hours prior to birth.
If labour continues beyond 4 hours then penicillin (2.5 million units) should be
administered every 4 hours until delivery. Clindamycin 900mg IV every 8 hours or
erythromycin 500 mg IV every 6 hours until delivery
are recommended for women allergic to penicillin.
Risk factors include 1) preterm labor (< 37 weeks gestation), 2)
prolonged rupture of membranes > 18 hours, 3) maternal fever >
38.00C, 4) group B streptococcal bacteriuria during pregnancy and 5)
previous delivery of a newborn with group B streptococcal disease regardless of
current group B streptococcus colonization.
The
emerging resistance to erythromycin and clindamycin among group B streptococcal
strains is of concern suggesting that the currently recommended antibiotic
therapy for women with penicillin allergy may need modification.
The increased use of antibiotics in the perinatal period may lead to an
increased incidence of bacteria resistant to antibiotics that are currently used
as initial therapy for suspected perinatal infections.
ValidationThe Task Force and two lead authors arrived at the final decisions on recommendations unanimously. After CTF consensus was reached, 2 experts in the field reviewed the manuscript and their suggestions were incorporated into a subsequent draft of the manuscript. The Task Force reviewed the final draft of the manuscript in February 2001.
SponsorsThe
Canadian Task Force on Preventive Health Care is funded through a partnership
between the Provincial and Territorial Ministries of Health and Health Canada.
Selected
ReferencesShah, V, Ohlsson, A with the Canadian Task Force on Preventive Health Care. Prevention of early-onset group B streptococcal (GBS) infection in the newborn: systematic review & recommendations. CTFPHC Technical Report #01-6. May, 2001. London, ON: Canadian Task Force.
Link to Published Recommendation Statement
Link to Full Technical Report (in pdf)
Link to Summary Table of Recommendations of this review
Link to Selected References list of this review
Copyright © 2000 Canadian
Task Force on Preventive Health Care
For any technical issues please contact: webmaster@ctfphc.org
Last modified: August 05, 2003
