Preterm labour - is bacterial vaginosis involved?
Objective. To assess the efficacy of treatment of bacterial vaginosis (BV) using metronidazole to reduce preterm labour in primiravidae and multigravidae with previous midtrimester abortion or preterm labour.
Design. Randomised controlled trial.
Setting. Tertiary academic hospital.
Method. Two different groups of patients were screened for BV at the first antenatal visit, namely primigravidae and high-risk multigravidae who had had a previous midtrimester abortion or preterm delivery. Patients where BV was diagnosed clinically or on Gram's stain of a smear taken from the posterior vaginal fornix, received either 400 mg metronidazole, or 100 mg vitamin C orally twice daily for 2 days. The Gram's stain was repeated after 4 weeks. If BV W?S found again, treatment with the same drug was repeated.
Outcome measures. Preterm delivery, birth weight and perinatal deaths.
Results. One thousand and five patients entered the study, but 40 were excluded for various reasons and 10 were lost to follow-up. There were 464 primigravidae, of whom 150 (32%) had BV. Except for the 5-minute Apgar score, no significant differences were found between primigravidae negative for BV and those who received either metronidazole or vitamin C. There were 491 high-risk multigravidae, of whom 127 (26%) had BV. The mean gestational age in the BVnegative group was 37 weeks, in contrast to 37.4 weeks in the vitamin C group and 35.6 weeks in the metronidazole group. Birth weights in these three groups were 2 752 g, 2 759 g and 2 475 g respectively, significantly less (P == 0.0109) in the metronidazole group in comparison with the BV-negative group. Delivery before 37 weeks occurred in 29% of high-risk multigravidae with no BV but in 24% of those who took vitamin C and in 43% who took metronidazole. Differences were significant between the BV-negative and metronidazole groups (P = 0.0231) and also between the metrol'.idazole and vitamin C groups (P = 0.0274). Delivery before 28 weeks occurred in 4% of the high-risk multigravidae with no UV but in 10% of those with BV who took metronidazole. The difference was significant (P =0.0430). Analysis for maximum likelihood estimates for preterm labour identified only previous preterm labour or midtrimester abortion as risk factors.
Conclusion. Metronidazole does not seem to reduce the prevalence of preterm labour when given for BV before 26 weeks' gestation.
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