The influence of pregnancy on relapses in multiple sclerosis: a cohort study.

The influence of pregnancy on the relapse rate (number of relapses per person per year) in MS was analysed for 52 women who had a pregnancy during the disease. The relapse rate was lower during the pregnancy-year (9 months of pregnancy and 6 months immediately post partum) than the non-pregnancy time. There was a heterogeneous pattern during the pregnancy-year with a sharp decrease in the relapse rate observed during pregnancy and a slight non-significant increase in the puerperium: both these relapse rates were compared with figures observed in the same group of women during the non-pregnancy time. Pregnancy does not appear to be a period at greater risk for exacerbations but, on the contrary it seems to act, on the whole, as a protective event. These data allow physicians to provide reassuring counselling to women.