Pregnancy and multiple sclerosis.

The effect of pregnancy on the relapse rate of multiple sclerosis has been investigated. Obstetric and relapse histories of 52 women with clinically definite multiple sclerosis were obtained; there were 101 pregnancies of which 85 were at risk of a multiple sclerosis relapse. By comparing the number of relapses in the pregnancy period (9 months of pregnancy and 6 months immediately post partum) with the number in non-pregnancy periods for the same women, no increased risk of relapse during the pregnancy period was demonstrated. However, of the relapses that did occur during the pregnancy period, there was a significant reduction in the number of relapses in the first and second trimesters.