'Trans-fats increase risk of womb disease'

But fats found in oily fish may protect against the condition, say scientists.

Endometriosis affects about 10 per cent of women and occurs when pieces of the uterus lining appear outside the womb.

The tissue grows during the menstrual cycle, but becomes trapped. In some cases the condition causes severe pain and leads to infertility.

Experts are still trying to understand the causes of endometriosis, and find a cure.

The new US study involved 70,709 American nurses who were monitored for 12 years.

Scientists found that those who consumed the most trans-fats in their diets were 48 per cent more likely to suffer endometriosis than those who ate the least.

In contrast, women with the highest intake of long-chain omega-3 fatty acids were 22 per cent less likely to be diagnosed with the condition than those with the lowest.

Study leader Dr Stacey Missmer, from Brigham and Women's Hospital and Harvard Medical School in Boston, said: "

Many women have been searching for something they can do for themselves, or their daughters, to reduce the risk of developing the disease, and these findings suggest that dietary changes may be something they can do."

Trans-fats are made through a process called hydrogenation, which turns liquid vegetable oil into solid fat.

Trans-fats are not banned from the UK but British consumption is low compared with that in the US.

A total of 1,199 women were diagnosed with endometriosis by the end of the study. The findings, published yesterday in the journal Human Reproduction, were adjusted to take account of the effect of factors such as total calorie intake, body mass, numbers of children, and race.