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Antibiotics for treating bacterial vaginosis in pregnancy

  • Review
  • Intervention


  • H McDonald,

    Head, Microbiology Diagnostic Unit, Corresponding author
    1. Women's and Children's Hospital, Microbiology and Infectious Diseases, North Adelaide, South Australia, AUSTRALIA
    • H McDonald, Head, Microbiology Diagnostic Unit, Microbiology and Infectious Diseases, Women's and Children's Hospital, Women's & Children's Hospital, 72 King William Road, North Adelaide, South Australia, 5006, AUSTRALIA.

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  • P Brocklehurst,

  • J Parsons,

  • R Vigneswaran



Bacterial vaginosis is an imbalance of the normal vaginal flora with an overgrowth of anaerobic bacteria and a lack of the normal lactobacillary flora. Bacterial vaginosis during pregnancy has been associated with poor perinatal outcome and, in particular, preterm birth. Identification and treatment may reduce the risk of preterm birth and its consequences.


To assess the effects of antibiotic treatment of bacterial vaginosis in pregnancy.

Search strategy

We searched the Cochrane Pregnancy and Childbirth Group trials register (September 2002).

Selection criteria

Randomized trials comparing antibiotic treatment with placebo or no treatment, or comparing two or more antibiotic regimens in pregnant women with bacterial vaginosis.

Data collection and analysis

Two reviewers assessed trials and extracted data independently. Study authors were contacted for additional information.

Main results

Ten trials involving 4249 women were included; all were of good quality. Antibiotic therapy was effective at eradicating bacterial vaginosis during pregnancy (odds ratio (OR) 0.21, 95% confidence interval (CI) 0.18 to 0.24, eight trials of 3825 women). Treatment did not significantly reduce the risk of preterm birth before 37 weeks (OR 0.95, 95% CI 0.82 to 1.10, eight trials of 4062 women), 34 weeks (OR 1.20, 95% CI 0.69 to 2.07, five trials of 851 women), or 32 weeks (OR 1.08, 95% CI 0.70 to 1.68, three trials of 3080 women). However, antibiotic treatment did significantly decrease the risk of preterm prelabour rupture of membranes (OR 0.32, 95% CI 0.15 to 0.67, three trials of 562 women). In women with a previous preterm birth, treatment did not affect the risk of subsequent preterm birth (OR 0.83, 95% CI 0.59 to 1.17, five trials of 622 women) but it did decrease the risk of preterm prelabour rupture of membranes (OR 0.14, 95% CI 0.05 to 0.38, two trials of 114 women) and low birthweight (OR 0.31, 95% CI 0.13 to 0.75, five trials of 622 women).

Reviewers' conclusions

Antibiotic treatment can eradicate bacterial vaginosis in pregnancy. However, the current evidence does not support screening and treating all pregnant women with asymptomatic bacterial vaginosis to prevent preterm birth and its consequences. For women with a previous preterm birth, there is little suggestion that detection and treatment of bacterial vaginosis will prevent a further preterm birth, but it may reduce the risk of low birthweight and preterm prelabour rupture of membranes.

Plain language summary


Antibiotics for infection in the birth canal does not reduce risk of babies being born too early

Bacteria are normally present in the birth canal (vagina) and usually cause no problems. If numbers of certain types of bacteria increase, this may cause an unpleasant discharge. It was thought this might cause some babies to be born too early (premature) and thus have problems struggling to survive. The review of trials found that antibiotics given to pregnant women reduced the number of bacteria in the woman's birth canal, although this may happen without treatment too. Giving antibiotics did not affect the numbers of babies who were born too early.