Effect of Pregnancy on Multiple Sclerosis

Abstract & Commentary

Synopsis: The rate of relapse in women with multiple sclerosis declines during pregnancy—most markedly in the third trimester.

Source: Confavreux C, et al. N Engl J Med 1998;339: 285-291.

To determine the effect of pregnancy on the occurrence of relapse and disease progression in young women with multiple sclerosis (MS), investigators in 12 European countries (the Pregnancy in Multiple Sclerosis [PRIMS] group) studied 254 women during 269 pregnancies. The rate of relapse during the year before pregnancy, during each trimester of pregnancy, and for up to one year after delivery was determined. Short courses of glucocorticoids were the only treatment allowed during gestation.

Overall, pregnancy outcome in women with MS was good with no increase in perinatal deaths, preterm deliveries, or fetal malformations. In the study group of 227 first pregnancies, the rate of relapse in the first and second trimesters of pregnancy (0.5 relapses per woman per year and 0.6 relapses per woman per year, respectively) was no different from the rate of relapse in the year prior to the pregnancy (0.7 relapses per woman per year). Importantly, the rate of relapse during the last trimester of pregnancy was significantly lower (0.2 relapses per woman per year). In the first three months after delivery, the rate of relapse rose significantly to 1.2 relapses per woman per year but, for the remainder of the first year, postpartum was no different from that prior to gestation. Epidural analgesia did not increase the risk of relapse after delivery while, in the 122 women who breast-fed their infants, the rate of relapse was significantly lower.

Confavreux and colleagues conclude that the rate of relapse in women with multiple sclerosis declines during pregnancy, most markedly in the third trimester. Relapses are more common during the first three months postpartum. Breast-feeding may reduce the risk of relapse, while epidural analgesia has no effect.

Comment by Steven G. Gabbe, MD

This important prospective study provides information that will be of great help in counseling young people with multiple sclerosis. This disorder, characterized by inflammation, demyelination, and axonal damage in the central nervous system, is twice as common in women as men. That the likelihood of relapse was not increased in pregnancy and was not altered by the use of epidural analgesia is reassuring. The rate of relapse did increase in the first three months postpartum—indicating a need for closer follow-up and prophylactic treatment soon after delivery. Breast-feeding appears to have a beneficial effect on the rate of relapse and can be encouraged in these patients. The beneficial effect of pregnancy seen in multiple sclerosis and rheumatoid arthritis is likely due to a relative increase in anti-inflammatory helper T cells as compared to pro-inflammatory helper T cells. This change is reversed in the postpartum period.