Having children could slow down the progression of multiple sclerosis (MS), research suggested today.

The disease, which affects around 100,000 people in the UK, is around twice as common in women as men and mostly affects females of childbearing age.

Previous studies on the long-term effects of childbirth on MS have produced mixed results, making it difficult to draw conclusions.

In the short term, women have been found to experience fewer relapses while pregnant, especially in the final 12 weeks of pregnancy.

However, they have also been found to suffer more relapses in the first three months of their child's life.

In the latest study, 330 women were split into four groups according to whether they had children only after developing MS, had them only before developing MS, had children either before or after developing symptoms or had no children at all.

All the groups were then assessed against the Expanded Disability Status Scale (EDSS), which measures progression of MS.

After around 18 years, 55% of women had reached EDSS 6, which means they required an aid such as a cane or crutch to walk about 100 metres, with or without resting.

Women having children after onset of MS were 39% less likely to have progressed to EDSS 6 than those who never had children, the results showed.

Meanwhile, those who gave birth before or after their first symptoms were 34% less likely to have developed to EDSS 6.

The researchers, from the Netherlands and Belgium, said: "The present study of 330 women with a mean follow-up of 18 years after disease onset suggests that patients who deliver one or more children after disease onset may have a more benign disease course as expressed by either the time to reach EDSS 6 from onset of disease or the age at which EDSS 6 is reached compared with those who had no children after disease onset.

"Moreover, women who gave birth at any point in time had less disability progression than those who never had children."

All the women had their first MS symptoms between the ages of 22 and 38. Even when age was taken into account, the researchers found similar results for the groups of women.

The research was published in the Journal of Neurology, Neurosurgery and Psychiatry.

Dr Susan Kohlhaas, research communications officer at the MS Society, said there were flaws in the study, including that researchers did not take into the influence of lifestyle factors or the types of drugs the women were taking.

The sample size was also too small.

She said: "It is difficult to form any meaningful conclusions from this research, given the small size of the study and its flaws, but further studies will hopefully clarify the effects of pregnancy in women with MS."