Influence of bacterial vaginosis on conception and miscarriage in the first trimester: cohort study
Bacterial vaginosis, a form of inflammation of the vagina caused by bacteria, increases the risk of miscarriage in the early stages of pregnancy, say researchers in this week's BMJ. In their study of over 850 women undergoing in vitro fertilisation (IVF) in Leeds, Dr Susan Ralph and colleagues from Leeds General Infirmary found that even though bacterial vaginosis did not affect conception, it was associated with a two-fold risk of miscarriage in the first trimester.
Bacterial vaginosis is the most common cause of abnormal discharge among women of childbearing age and prevalence rates of between 13 and 31 per cent have been reported in pregnant women, say the authors. In their study they found that 24.6 per cent of women had bacterial vaginosis, but that there was no difference in the conception rate between these women and those with normal vaginal bacteria (flora).
However, say Ralph et al, 31.6 per cent of the women studied with bacterial vaginosis had a significantly increased risk of miscarriage in the first trimester as opposed to 18.5 per cent of women with normal vaginal flora. This increased risk remained significant even after the researchers accounted for factors known to increase miscarriage, such as increasing maternal age, smoking, polycystic ovaries and a past history of three or more miscarriages.
The authors conclude that their study is the first to describe a definite association between bacterial vaginosis and miscarriage in the first trimester, however, they concede that they are still not clear how this condition affects miscarriages. They speculate that the cause is most likely to be due to pre-existing endometritis (inflammation inside the uterus) which affects the implantation of the fertilised egg in the IVF process or its early embryonic development. They suggest that this phenomenon could also be relevant to naturally conceived pregnancies and call for further research to be conducted in this area.
Contact:
Dr Janet Wilson, Consultant Physician, Department of Genitourinary Medicine, General Infirmary at Leeds, Leeds Email: jdwilson@dunham.freeuk.com