Background & Objectives : Bacterial vaginosis is a condition which is determined by changes in microbial ecosystem of vagina and is considered as a preventable risk factor for preterm delivery. This study was conducted to assess the effectiveness of bacterial vaginosis screening program in routine prenatal care and its effect on decreasing preterm labor.

  Methods: This clinical trial study was conducted on 474 pregnant women at gestational stage between 2007 and 2008. The participants were randomly divided into 2 groups: intervention group and control group. Screening was performed in intervention group with Amsel's criteria (3 of 4 needed for diagnosis). Positive cases were given clindamycin cream (2%) for one week. The outcome of the delivery was assessed in both groups afterward. Data were analyzed by SPSS11 software using descriptive statistics.

  Results: There was no significant difference between two groups regarding pregnancy rank, wanted and unwanted pregnancy, insufficient weight gain, mother vaccination and complication of pregnancy. Bacterial vaginosis was observed in 17 out of 216 (8%) in the intervention group and then treated. Prevalence of preterm delivery in the intervention and control groups were 3 (1.4%) and 12 (4.7%), respectively. The relative risk was protective (RR: 0.3, DR: 0.033, NNT: 30).

  Conclusion: Screening and treatment of bacterial vaginosis in pregnant women could significantly decrease the rate of preterm delivery.