Intrapartum antibiotics for Group B streptococcal colonisation

Smaill F

 Date of most recent amendment: 25 February 1999
Date of most recent substantive amendment: 05 December 1994

 This review should be cited as: Smaill F. Intrapartum antibiotics for Group B streptococcal colonisation (Cochrane Review). In: The Cochrane Library, Issue 4, 2003. Chichester, UK: John Wiley & Sons, Ltd.

Group B streptococcal infection remains a significant cause of neonatal morbidity and mortality. Maternal colonization with group B streptococci is a recognized risk factor for neonatal colonization and sepsis. Colonized women who experience either a long duration of membrane rupture, premature delivery or intrapartum fever are at particularly high risk for transmitting group B streptococcus to their infants.

To study the effect of intrapartum antibiotics given to women colonized with group B streptococcus on:

1. Infant colonization with group B streptococcus.

2. Early onset group B streptococcal sepsis.

3. Neonatal deaths from infection.

Types of studies

All trials were included where the intention was to allocate participants randomly to treatment or no treatment.

Types of participants

Pregnant women found on screening to be colonized with group B streptococcus. The methods for identifying women as colonized with group B streptococcus and eligible for intrapartum treatment varied considerably. One study only included women if they had premature labour or prolonged rupture of membranes (Boyer 1986); the others gave treatment to both high and low risk women. In two studies, a screening culture was done early in the pregnancy (most before 31 - 33 weeks). Two studies (Morales 1986; Tuppurainen 1989) identified patients using a rapid screening test in labour, although it took up to 24 hours for results to be available. The other three studies cultured specimens using selective media and identified group B streptococcus using standard methods. Both rectal and vaginal cultures were performed in three studies (Boyer 1986; Easmon 1983; Matorras 1991); the other two only used vaginal cultures.

Types of intervention

Studies were included where systemic antibiotic treatment or no treatment was given intrapartum. Ampicillin 1g intravenously every 6 hours during labour was the usual regimen; alternatives included benzyl penicillin or erythromycin. In one study (Boyer 1986) ampicillin was also given to the infants of treated mothers.

Types of outcome measures

Only studies that included infant colonization with group B streptococcus and/or infant infection were included.

See: Cochrane Pregnancy and Childbirth Group search strategy

This review has drawn on the search strategy developed for the Pregnancy and Childbirth Group as a whole.

Relevant trials were identified in the Group's Specialised Register of Controlled Trials. See Review Group's details for more information.

Information on method of allocation, characteristics of participants, type of intervention, and outcomes were abstracted from eligible studies by the reviewer. Pooled odds ratios (OR) for dichotomous outcomes were calculated by Peto's one step method, using a fixed effects model.

See Characteristics of Included Studies. Five studies met the inclusion criteria and were included. Where there was more than one published reference that, in the opinion of the reviewer (Fiona Smaill), referred to the same patient population, the most detailed reference was used.

In none of the studies was blinding of randomization adequately assured and this may have introduced selection bias. None used a placebo and there was no attempt to blind the observer. Although the outcomes (colonization and sepsis) are unambiguous, observer bias cannot be excluded. In most instances complete follow-up was achieved but it was not clear in all studies how many eligible patients had not been enrolled.

The use of intrapartum antibiotics has been shown in these studies to reduce infant colonization rate. The studies also showed a reduction in early onset neonatal infection, a more relevant clinical endpoint than surface colonization. The direction of effect for both colonization and infant sepsis was consistent across all trials. There were insufficient numbers to detect a difference in neonatal mortality.

Intrapartum antibiotics will reduce the transmission of group B streptococcus. The studies reviewed show an effect when women who are receiving comprehensive obstetrical care and are known to be colonized with group B streptococcus are treated. These results are not generalizable to the whole pregnant population, particularly those women without antenatal care who are admitted in labour and deliver before the results of cultures are available.

The rate of infant GBS sepsis in the control groups of the studies where this outcome was reported ranged from 2 - 9%. This is higher than the overall infection rates of 1 - 2% that are reported in babies whose mothers are colonized with GBS, raising questions as to how representative the populations studied were. Only one of the studies included just women with risk factors for GBS disease, the others did not differentiate between high risk and low risk pregnancies.

The methodological quality of the studies included was poor and there was potential for a high risk of bias. Only one study adequately addressed concealment of allocation and no study was blinded. No study adequately addressed the potential for adverse consequences of prophylaxis.

Implications for practice

The results of this review suggest intrapartum antibiotic treatment of women colonized with group B streptococcus will reduce infant colonization and neonatal infection. The Centers for Disease Control and Prevention (CDC 1996) currently include in their guidelines the recommendation that any woman in preterm labour (<37 weeks) and any woman who is known to be colonized with GBS receive intrapartum antibiotics and that antibiotics also be given to any woman with intrapartum fever or prolonged rupture of membranes if culture results are not available. Other expert guidelines do not advocate the administration of intrapartum antibiotics to all colonized women unless recognized risk factors are present. Good evidence to support any one strategy is not available from controlled trials.

Implications for research

Effective strategies to detect maternal colonization with Group B streptococcus are necessary if guidelines for intrapartum antibiotic administration are to be successfully implemented. The optimal time and method to detect maternal colonization with group B streptococcus is unknown. A combined ano-rectal and vaginal swab, collected at 35 - 37 weeks, and processed using a selective enrichment broth media has been recommended. The availability of a sensitive rapid screening test to detect accurately women in labour who are colonized with GBS would make prevention strategies more efficient, but the available tests still lack acceptable performance characteristics.

Whether prophylaxis should only be given to women with identified risk factors or to all women colonized with GBS has not been satisfactorily established. Better data on maternal risk factors for neonatal GBS in different populations are needed if the impact of different prevention strategies is to be more accurately evaluated.

None.

None known.

Characteristics of included studies

IV = intravenous
IM = intramuscular

Characteristics of excluded studies

References to studies included in this review

Boyer 1986 {published data only}

Boyer KM, Gadzala CA, Kelly PD, Gotoff SP. Selective intrapartum chemoprophylaxis of neonatal group B streptococcal early-onset disease. III. Interruption of mother-to-infant transmission. J Infect Dis 1983;148:810-816.

Boyer KM, Gotoff SP. Prevention of early-onset neonatal group B streptococcal disease with selective intrapartum chemoprophylaxis. N Engl J Med 1986;314:1665-1669.

Easmon 1983 {published data only}

Easmon CSF, Hastings MJG, Deeley J, Bloxham B, Rivers RPA, Marwood R. The effect of intrapartum chemoprophylaxis on the vertical transmission of group B streptococci. Br J Obstet Gynaecol 1983;90:633-635.

Matorras 1991 {published data only}

Matorras R, Garcia-Perea A, Madero R, Usandizaga JA. Maternal colonization by group B streptococci and puerperal infection: analysis of intrapartum chemoprophylaxis. Eur J Obstet Gynaecol Reprod Biol 1990;38:203-207.

Matorras R, Garcia-Perea A, Omenaca F, Diez-Enciso M, Medero R, Usandizaga JA. Intrapartum chemoprophylaxis of early-onset group B streptococcal disease. Eur J Obstet Gynaecol Reprod Biol 1991;40:57-62.

Omenaca Teres F, Matorras R, Garcia-Perea A, Elorza MD. Prevention of neonatal group B streptococcal sepsis. Pediatr Infect Dis 1987;6:874.

Morales 1986 {published data only}

Lim DV, Morales WJ, Walsh AF, Kazanis D. Reduction of morbidity and mortality rates for neonatal group B streptococcal disease through early diagnosis and chemoprophylaxis. J Clin Microbiol 1986;23:489-492.

Morales WJ, Lim DV, Walsh AF. Prevention of neonatal group B streptococcal sepsis by the use of a rapid screening test and selective intrapartum chemoprophylaxis. Am J Obstet Gynecol 1986;155:979-983.

Tuppurainen 1989 {published data only}

Tuppurainen N, Hallman M. Prevention of neonatal group B streptococcal disease: intrapartum detection and chemoprophylaxis of heavily colonized parturients. Obstet Gynecol 1989;73:583-587.

Tuppurainen N, Osterlund K, Hallman M. Selective intrapartum penicillin prophylaxis of early onset group B streptococcal disease. Pediatr Res 1986;20:403A.

References to studies excluded from this review

Dykes 1987

Dykes AK, Christensen KK, Christensen P. Chlorhexidine for prevention of neonatal colonization with group B streptococci. IV. Depressed puerperal carriage following vaginal washing with chlorhexidine during labour. Eur J Obstet Gynecol Reprod Biol 1987;24:293-297.

Merenstein 1980

Merenstein GB, Todd WA, Brown G, Yost CC, Luzier T. Group B beta-hemolytic streptococcus: randomized controlled treatment study at term. Obstet Gynecol 1980;55:315-318.

Additional references

Allen 1993

Allen UD, Navas L, King SM. Effectiveness of intrapartum penicillin prophylaxis in preventing early-onset group B steptococcal infection: results of a meta-analysis. Can Med Assoc J 1993;149:1659-1665.

CDC 1996

Centers for Disease Control and Prevention. Prevention of perinatal group B streptococcal disease: a public health perspective. MMWR. 1996;45(No RR-7).

Ohlsson 1994

Ohlsson A, Myhr TL. Intrapartum chemoprophylaxis of perinatal group B streptococcal infections: a critical review of randomized controlled trials. Am J Obstet Gynecol 1994;170:910-917.

Wang 1989

Wang E, Smaill F. In: Chalmers I, Enkin M, Keirse MJNC, editor(s). Effective Care in Pregnancy and Childbirth. Oxford: Oxford University Press, 1989:534-564.

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External sources of support

• No sources of support supplied

Internal sources of support

• No sources of support supplied

Medical Subject Headings (MeSH)

Antibiotics [therapeutic use]; Disease Transmission, Vertical [prevention & control]; Infant, Newborn ; Pregnancy Complications, Infectious [drug therapy]; Streptococcal Infections [drug therapy] [transmission]; Streptococcus agalactiae

Mesh check words: Female Human Pregnancy

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