New research suggests that pregnancy may decrease women's risk of developing multiple sclerosis.
In an Austrailian study of 282 people with MS symptoms, having one pregnancy was associated with nearly halving the risk of developing MS symptoms compared to those who were never pregnant. Risk discreased even more with additional pregnancies, according to the study.
Study author Anne-Louise Ponsonby, head of the environmental and genetic epidemiology and research group at Murdoch Children's Research Institute inMelbourne,Australia, and her research team reported they found an association between pregnancy and a lower risk of MS symptoms, not a direct cause-and-effect link.
Previous research has found that pregnancy in women who already have MS is linked with lower rates of relapse. The researchers say 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,” said Ponsonby.
Researchers reviewed information about 282 Australian men and women between the ages of 18 and 59 who had a first diagnosis of central nervous demyelination, which means they had their first symptoms similar to MS but had not yet been diagnosed with the disease. They were compared to 542 men and women with no 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.
The study found that women who were pregnant two or more times had a quarter of the risk of developing MS symptoms and women who had five or more pregnancies had one-twentieth the risk of developing symptoms than women who were never pregnant. There was no association between the amount of children and risk of MS symptoms in men.
“The rate of MS cases has been increasing in 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 have in past years,” said Ponsonby.
The researchers couldn't say exactly why pregnancy may lower MS risk, but they speculated it could be the increase in estrogen during pregnancy or the effect pregnancy has on inflammatory genes involved in MS.
The information may lead to future studies looking into hormonal treatment or other treatments that may alter the disease course.
The study was published online in the journal Neurology.