Recent use of oral contraceptives and current pregnancy may lower the risk of developing MS, while the postpartum period may be a time of higher risk of MS onset, new research suggests.

Estrogen was found to delay the onset and change the progress of a disease similar to MS in animals in earlier research. This led to the hypothesis that oral contraceptives containing estrogen might affect risk or alter the course of the disease in humans.

Similarly, a woman's risk might be lower during pregnancy and higher during the postpartum period, during which times profound hormonal changes are known to occur, according to background information in the article.

40 Percent Lower

Using a research database that includes medical and pharmacy records for three million Britons, Álvaro Alonso, MD, Ph.D, of the Harvard School of Public Health, Boston, and colleagues compared 106 women who received a new diagnosis of MS between January 1993 and December 2000 with 1,001 matched women who did not have MS.

"The incidence of MS in OC users was 40 percent lower than in nonusers," the authors report.

"Women had a higher risk of developing first symptoms of MS in the six months following a pregnancy and a non-significant lower risk during pregnancy, compared with those with no pregnancy," the researchers observe, noting that "this is consistent with studies on the effect of pregnancy in patients with MS and the immunological changes associated with pregnancy."

Higher Risk Postpartum

"Recent OC use and, possibly, current pregnancy are associated with a lower risk of developing MS," the authors state.

"On the contrary, the postpartum period confers a higher risk of MS onset. Our findings suggest that high levels of exogenous (from outside the body) estrogens from OC use and of endogenous (from the body) estrogens during pregnancy may delay the first clinical attack of MS," they conclude.