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Multiple pregnancies linked to decreased risk of MS

Research News
Friday, March 9, 2012
A study by Murdoch Children's Research Institute has found that women's risk of getting multiple sclerosis (MS), drops as the number of pregnancies they have had increases.

The study, which is published in Neurology, involved more than 800 women between the ages of 18 and 60. Nearly 300 of them had experienced a first episode of MS symptoms. For women, the number of pregnancies lasting at least 20 weeks and the number of live births were recorded. For men, the number of children born was recorded.

It found women in the study with at least one child had about half the risk of early MS symptoms compared to women without children. And that risk appeared to drop with each additional child. Women with three children had a 75 per cent lower risk of early MS symptoms compared to women without children.

Those benefits remained even after researchers accounted for other factors associated with the likelihood of developing MS, like smoking, skin damage and sun exposure, and certain susceptibility genes. In a contrasting assessment for men, number of live born children did not relate to risk of a first demyelinising event, helping to exclude possible factors linked to larger family size such as socioeconomic status.

Lead researcher, Anne-Louise Ponsonby said they found an association between pregnancy and a lower risk of MS symptoms, not a direct cause-and-effect link. She said, however, that this association may help explain why the incidence of MS in women has inched up over the past few decades, as more women delay pregnancy or have fewer babies or none at all.

"In our study, the risk went down with each pregnancy and the benefit was permanent. Even one pregnancy was associated with nearly a halving of risk of developing MS symptoms," Anne-Louise said.

"The rate of MS has been increasing particularly among women over the last few decades, and our research suggests that this may be due to mothers having children later in life and having fewer children than they've had in past years."

Researchers say more work is now needed to better understand exactly why pregnancy may lower MS risk; including the effect pregnancy has on inflammatory genes that may be involved in MS.