Antibiotic prophylaxis to prevent post-abortal upper genital tract infection in women with bacterial vaginosis: randomised controlled trial

Objective To determine the prevalence of bacterial vaginosis in women undergoing first trimester suction termination of pregnancy and to evaluate the efficacy of metronidazole in reducing the risk of post abortal pelvic infection in women with bacterial vaginosis. Design Randomised double-blind placebo-controlled trial. Setting Two teaching hospitals and one district general hospital. Sample Two hundred and seventy-three women with bacterial vaginosis undergoing termination of pregnancy. Methods Women with bacterial vaginosis, diagnosed using modified Spiegel's criteria, were individually randomised to receive either a 2 g metronidazole suppository or identical placebo per-operatively. Participants, doctors and investigators were blinded to treatment allocation. Participants were asked to complete a questionnaire about post-operative symptoms, visits to the general practitioner, antibiotic treatment, readmission to hospital, contraception and emotional response after one month. Results The prevalence of bacterial vaginosis was 29.3% (326/1111). Intention-to-treat analysis showed that post-operative upper genital tract infection developed in 12/142 (8.5%) women allocated to metronidazole and 21/131 (16.0%) women randomised to placebo, a difference of 7.6% (95% confidence intervals -15.4 to +0.2%; relative risk 0.53, 0.27 to 1.03, P = 0.055). The effect of prophylaxis was similar when the analysis was restricted to women receiving the allocated treatment and with complete follow up. There was no difference in the risk of readmission to hospital and the frequencies of self reported symptoms in the two groups were similar. Conclusion This randomised placebo-controlled trial among women with bacterial vaginosis provides weak evidence that metronidazole decreases the risk of upper genital tract infection after first trimester suction termination of pregnancy but a chance finding could not confidently be excluded. Large well-conducted randomised trials with long term outcome measures are now needed to determine the most effective antibiotic combinations and strategy for prevention of post-abortal pelvic infection.