Primary care

Association between bacterial vaginosis or chlamydial infection and miscarriage before 16 weeks' gestation: prospective community based cohort study

Pippa Oakeshott, senior lecturer in general practice, ^a Phillip Hay, senior lecturer, ^b Sima Hay, research midwife, ^a Frances Steinke, research health visitor, ^a Elizabeth Rink, senior lecturer in primary care, ^a Sally Kerry, senior lecturer in medical statistics. ^a

^a Department of General Practice and Primary Care, St George's Hospital Medical School, London SW17 0RE, ^b Department of Genitourinary Medicine, St George's Hospital Medical School

Correspondence to: P Oakeshott oakeshot{at}sghms.ac.uk

Objectives: To assess whether bacterial vaginosis or chlamydial infection before 10 weeks' gestation is associated with miscarriage before 16 weeks.
Design: Prospective cohort study.
Setting: 32 general practices and five family planning clinics in south London.
Participants: 1216 pregnant women, mean age 31, presenting before 10 weeks' gestation.
Main outcome measure: Prevalence of miscarriage before 16 weeks' gestation.
Results: 121 of 1214 women (10.0%, 95% confidence interval 8.3% to 11.7%) miscarried before 16 weeks. 174 of 1201 women (14.5%, 12.5% to 16.5%) had bacterial vaginosis. Compared with women who were negative for bacterial vaginosis those who were positive had a relative risk of miscarriage before 16 weeks' gestation of 1.2 (0.7 to 1.9). Bacterial vaginosis was, however, associated with miscarriage in the second trimester at 13-15 weeks (3.5, 1.2 to 10.3). Only 29 women (2.4%, 1.5% to 3.3%) had chlamydial infection, of whom one miscarried (0.32, 0.04 to 2.30).
Conclusion: Bacterial vaginosis is not strongly predictive of early miscarriage but may be a predictor after 13 weeks' gestation. The prevalence of Chlamydia was too low to assess the risk, but it is unlikely to be a major risk factor in pregnant women.

What is already known on this topic Miscarriages are common and associated with considerable morbidity and costs Bacterial vaginosis is associated with miscarriage after 16 weeks' gestation and preterm birth but the role of chlamydial infection is uncertain What this study adds Bacterial vaginosis is not a strong predictor of miscarriage before 16 weeks' gestation but may be associated with miscarriage at 13-15 weeks' gestation The prevalence of chlamydial infection was too low for it to be a major risk factor for miscarriage in this population of healthy pregnant women Non-invasive screening for bacterial vaginosis and chlamydial infection by using self administered vaginal swabs is feasible in pregnant women in the community