Friday, July 23, 1999 Published at 00:06 GMT 01:06 UK
Infection increases miscarriage risk
Bacterial vaginosis poses a risk to a successful pregnancy
Pregnant women who contract a common bacterial infection of the vagina are more likely to miscarry in the early stages of pregnancy, researchers have found.
Bacterial vaginosis, a form of inflammation of the vagina, is the most common cause of abnormal discharge among women of childbearing age. It affects 13% to 31% of pregnant women.
Dr Susan Ralph and colleagues from Leeds General Infirmary found that the infection can double the risk of miscarriage in the first three months of pregnancy. However, it had no impact on conception.
The researchers studied 850 women undergoing in vitro fertilisation (IVF) in Leeds.
Writing in the British Medical Journal, they report that 24.6% of the women had bacterial vaginosis.
These women conceived at the same rate as women with normal vaginal bacteria.
However, 36% of those with the infection subsequently miscarried, compared to only 18% of women who were free of infection.
Previous research has linked bacterial vaginosis to an increased risk of premature birth.
The authors are not clear how this condition affects miscarriages.
However, one of the researchers Dr Janet Wilson, a consultant physician specialising in genito-urinary medicine, said it was possible that the infection caused endometritis, an inflammation of the uterus.
She said: "This could spread up into the womb, causing inflammation of the lining of the womb and releasing various chemicals which would make a hostile environment for a fertilised egg that was trying to grow."
One of those chemicals, tumour necrosis factor alpha, causes the blood vessels to constrict, effectively starving the fertilised egg of vital nutrients.
The way that bacterial vaginosis is transmitted is unclear. Some believe it can be passed on through sexual activity, although the organisms responsible also have been found in young women who are not sexually active.
Many women carry the bacteria which cause the infection, but at low levels which pose no risk.
Dr Wilson said women who planned to get pregnant should seek medical advice about the infection, which is easily treatable with antibiotics.