Researchers have found that obesity raises miscarriage risk and that obese women who have had a miscarriage are at greater risk of miscarrying again if they didn't lose any weight.

A team of researchers from London's St Mary's Hospital decided to watch the progress of 696 women whose miscarriages had been classified as "unexplained". They found that the risk of another miscarriage has risen by 73% if the woman was obese.

However, they warn that losing weight in pregnancy may be as risky and dangerous.

The links between obesity and conceiving as well as complications during pregnancy have long been known but this new study has specifically set its eyes on "recurrent" miscarriages, for which there is often no obvious cause.

In the study of 696 women, more than half were of "normal" weight, 30% were overweight, and 15% were obese.

The results showed that the older the woman was, the higher chances of having another miscarriage, but, when the figures were adjusted to account for this, obesity showed up as another possible factor.

Interestingly, there was no difference in the miscarriage rates for overweight, normal and underweight women while the risk of further miscarriage increased sharply for obese women.

The researchers now advise that all women with recurrent miscarriage should be weighed and those who are found obese, with BMI over 30, should be thought of benefits of losing weight.

Besides raising the risks of miscarriage, obesity was also linked to fetal malformation and other adverse pregnancy outcomes. While the exact causes are not known, it is quite possible that the increased inflammation could be harming the chances of a successful pregnancy.