Pregnancy and multiple sclerosis. A prospective study

To conduct a prospective assessment of pregnancy on women with multiple sclerosis (MS), focusing on pregnancy outcome and relapses during gestation and up to 6 months after delivery.

Expected numbers of relapses were based on data for (1) "self-controls": the mothers ("cases") themselves prior to becoming pregnant and (2) "matched controls": female patients with MS "matched" to the mothers for year of birth, age of MS onset, MS type, MS course, and initial MS symptom(s).

Cases and controls were identified from an ambulatory care MS clinic that serves the province of British Columbia, Canada.

Women with a diagnosis of MS who attended the MS clinic during 1982 through 1986 and subsequently became pregnant during 1982 through 1989 inclusive were included in this study as cases. Matched controls were women with MS who attended the MS clinic during the same period but did not become pregnant.

No significant increase in relapse rate was found for cases during the first two trimesters of gestation. The number of relapses was significantly less than expected during the third trimester compared with matched controls (chi 2 = 6.80, df = 1, P < .02), but not compared with self-controls (chi 2 = 3.39, df = 1, P > .05). The observed number of relapses for the 6 months after delivery did not differ significantly from expected (self-controls: chi 2 = 2.84, df = 2, P > .05; matched controls: chi 2 = 1.76, df = 2, P > .05).

These data suggest that neither pregnancy nor the 6-month period after delivery is a risk factor for relapse in MS. They are consistent with previous observations that, in the long term, pregnancy does not influence subsequent MS disability.