The Pharmaceutical Journal
Vol 276 No 7384 p63
21 January 2006

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Do not use metronidazole to prevent delivery

Metronidazole should no longer be used in pregnancy for the prevention of pre-term delivery, according to the authors of a study published in the British Journal of Obstetrics and Gynaecology (2006;113:65).

Andrew Shennan of the Maternal and Fetal Research Unit, St Thomas’ Hospital, London, and colleagues screened 900 pregnant women at known risk of pre-term birth for vaginal fetal fibronectin — a consequence of uterine infection — at 24 and 27 weeks of gestation. Women with a positive result were randomised to receive a one-week course of metronidazole or placebo.

The researchers found that the risk of birth before 37 weeks of gestation was higher in the metronidazole group than in the placebo group (62 per cent versus 39 per cent, risk ratio 1.6, 95 per cent confidence interval 1.05–2.4; P=0.022). Although birth occurred earlier in the metronidazole group than in the placebo group, the difference in risk of birth before 30 weeks (the primary end point of the study) was not significant.

“There is evidence to suggest that the commonly used antimicrobial agent metronidazole when used alone has no benefit in the prevention of pre-term delivery in high risk women. Indeed, this and other trials suggest positive harm,” the researchers conclude. However, they point out that increasing gestation length is not always in the mother’s or baby’s best interest.

For example, 10 per cent of pregnancies with pre-term membrane rupture have evidence of fetal septicaemia, which is unlikely to respond to maternal antimicrobial therapy, they say.