TUESDAY, Nov. 24 (HealthDay News) -- Having children may slow the progression of multiple sclerosis, new research suggests.

Belgian researchers followed 330 women who had experienced their first MS symptoms between the ages of 22 and 38.

Women who had given birth to at least one child were 34 percent less likely to have the disease progress to a stage in which they needed walking assistance, such as a cane or brace, than women without children.

While having a baby either before or after the onset of MS symptoms seemed to help, women who had a child after they began experiencing MS symptoms were even better off. During the study, women with MS symptoms who'd had a baby were 39 percent less likely to have their disease progress to the point of needing walking assistance. In the study, women had the disease for an average of 18 years.

"Women with MS who have children seem to have a more benign MS course than those who don't," said study author Marie D'hooghe, of the department of neurology at Nationaal MS Centrum in Melsbroek, Belgium.

The research appears in the Nov. 24 online issue of the Journal of Neurology, Neurosurgery & Psychiatry.

Multiple sclerosis is an autoimmune disease in which the body's own defense system attacks myelin, or the protective fatty substance that surrounds nerve fibers in the central nervous system, according to the National Multiple Sclerosis Society. The damage causes a disruption to nerve signals traveling to and from the brain, which causes the numbness, walking problems, blurry vision and fatigue.

About 85 percent of those with MS start with a relapsing-remitting course, in which attacks are followed by partial or total recovery, according to the study. More than half go on to develop a more progressive form of the disease, in which symptoms worsen over time and there are fewer, shorter periods without symptoms. Eventually, the disease can lead to loss of vision and paralysis.

Women are twice as likely to develop MS as men, though women tend to have less severe cases than men, according to the study.

About three-quarters of the women in the study had children. The researchers measured the time it took for women to reach level 6 on the Expanded Disability Status Scale (EDSS), a rating system used by doctors to describe symptoms, with level 1 being the least severe and 10 being death due to MS. Level 6 is defined as needing a cane, crutch or brace to walk.

Women who did not have children took an average of 13 to 15 years to progress to EDSS 6, while women who had children took an average of 22 to 23 years to reach that stage, the researchers found.

"Having one or more children does seem to be beneficial," said Patricia O'Looney, director of biomedical research for the National Multiple Sclerosis Society. "But we don't know enough about the patient demographics to really draw some major conclusions."

Among the unknowns are the treatments the women in the study were getting for MS or if perhaps the women who decided to have children were feeling better and having fewer symptoms.

Though much remains to be learned about the role of pregnancy in MS, a possible reason why it may help slow the progression of the disease is that during pregnancy, the immune system is "downregulated," in part to prevent the mother's body from rejecting the fetus, O'Looney explained. Suppressing the immune system may also help to control MS, O'Looney noted.

Treatments for MS, such as interferon beta-1a and -1b, work by suppressing the immune system.

A second possibility for why childbirth might help delay the progression of MS is that during pregnancy, estrogen levels rise. Previous research has suggested estrogen may help protect from MS by stimulating the cells that make myelin. The MS Society is currently funding a clinical trial in which women with MS are given estriol, a form of estrogen, along with standard MS treatments.

"The sex hormones do seem to have some neuroprotective role, though we are not quite sure how," O'Looney said.

Still, O'Looney stressed that women should not interpret the results as reason to have a baby to delay the progression of the disease, or blame themselves if they decided not to have children.

"We still don't know a lot about the great variability of MS -- why does one person become more progressive while another follows a more benign course," O'Looney said. "What's certain is that one should not conclude it's based on whether or not you have a child. There are so many other factors, including possibly genetic factors, that determine that."

More information

The National Multiple Sclerosis Society has more on pregnancy and MS.

SOURCES: Marie D'hooghe, department of neurology, Nationaal MS Centrum in Melsbroek, Belgium; Patricia O'Looney, Ph.D., director, biomedical research, National Multiple Sclerosis Society; Nov. 24, 2009, Journal of Neurology, Neurosurgery & Psychiatry, online

Copyright © 2009 ScoutNews, LLC. All rights reserved.