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 under going first trimester suction termination of pregnancy and to evaluate the efficacy of metronidazole in reducing the risk of post abortal pelvic infec tion 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 undergo ing termination of pregnancy. Methods Women with bacterial vaginosis, diagnosed using modified Spiegel's criteria, were individually randomised to receive either a 2 g metronidazol e suppository or identical placebo per-operatively. Participants, doctors a nd investigators were blinded to treatment allocation. Participants were as ked to complete a questionnaire about post-operative symptoms, visits to th e general practitioner, antibiotic treatment, readmission to hospital, cont raception and emotional response after one month. Results The prevalence of bacterial vaginosis was 29.3% (326/1111). Intenti on-to-treat analysis showed that post-operative upper genital tract infecti on 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 in tervals -15.4 to +0.2%; relative risk 0.53, 0.27 to 1.03, P = 0.055). The e ffect 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 s elf reported symptoms in the two groups were similar. Conclusion This randomised placebo-controlled trial among women with bacter ial 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 ne eded to determine the most effective antibiotic combinations and strategy f or prevention of post-abortal pelvic infection.