Studies show that MS has no adverse effects on the course of pregnancy. In fact, symptoms often temporarily improve. Scientists believe this may be related to a natural suppression of the immune system that occurs in the uterus during pregnancy. This suppression is a mechanism that protects the fetus. Otherwise, a woman's immune system might identify her fetus as foreign tissue. MS is an autoimmune disease-a disease in which the body attacks its own tissues. That's why changes in a woman's immune system during pregnancy may be the reason for a temporary stabilization or remission of MS. A woman with MS may, however, be more likely to experience problems related to the disease after delivery. Doctors say between 20% and 40% of women with MS experience a relapse in the three months following childbirth. There is no evidence, however, that the overall course of disease is affected by pregnancy or childbirth. It is very important that women with MS discuss pregnancy or any plans to become pregnant with their doctors. One reason is that some drugs used to treat MS may cause birth defects. Also, some drugs can be passed to a child during breast feeding.
[source: NIH at http://www.ninds.nih.gov/disorders/multiple_sclerosis/detail_multiple_sclerosis.htm]
