How does pregnancy affect the course of multiple sclerosis?

Updated: Aug 20, 2019
  • Author: Carmel Armon, MD, MSc, MHS; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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An Israeli study of 338 women conducted to evaluate the MS relapse rate during each trimester of pregnancy and 6 months after delivery reported that of 199 completed pregnancies in 66 women, 85 were accompanied by relapses (20 during pregnancy, 65 post partum). [41] The relapse rate was definitely reduced in the third trimester.

In a later study, Salemi et al reported a significant reduction in the relapse rate during pregnancy. [42] Using a questionnaire, the investigators collected information concerning patient age at the onset of MS, duration of disease, number of relapses during the prepregnancy period, number of relapses during pregnancy, and number of relapses during the first 3 months after delivery. Out of 350 patients, 70 had 98 pregnancies.

The Pregnancy in Multiple Sclerosis (PRIMS) study was the first multicenter prospective study of MS in pregnant women. [43] In this study, the relapse rate declined by approximately 70% during the third trimester as compared with the rate in the year before conception. The researchers evaluated 254 women with relapsing-remitting MS during and after 269 pregnancies. Patients were examined at 20, 28, and 36 weeks’ gestation to determine the relapse rate in each trimester.

Roullet et al reported that MS relapses occurring during pregnancy tended to be mild, resulting in minimal or no residual deficits. [44] They examined the severity of relapses in 125 French women who were followed via an MS clinic over 10 years and who had a total of 32 full-term pregnancies.

Patients with MS appear to fare better when they are pregnant (particularly in the third trimester) than when they are not, with a decrease in the number and severity of relapses. Some authors claim that the suppression of MS seen during pregnancy may be more potent than that achieved with currently available treatments. [45]

Nevertheless, the decision whether to forgo treatment with immunomodulatory agents must be made on an individual basis. Given the potential risks these treatments pose for pregnant women, the decision to treat should be reserved only for exceptional cases (see Treatments during pregnancy).


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