Background: Multiple sclerosis (MS) is a disabling autoimmune disease of the central nervous system, typically affecting women of childbearing years. Although the disease course of MS is highly unpredictable, disease activity is almost invariably halted during pregnancy. After delivery, however, the relapse rate increases. Despite early recognition of this pattern of disease activity, its explanation remains a mystery.
Objective: The aim of this study was to elucidate the underlying mechanisms responsible for the amelioration of MS during pregnancy and for its reactivation after delivery.
Methods: This Finnish prospective study included clinical and immunologic follow-up of patients with MS during pregnancy and 6 months into the postpartum period. Groups of patients with MS who were not pregnant, along with pregnant and nonpregnant healthy women, served as controls. Laboratory investigations included subtype analysis of T, B, and natural killer (NK) cells during and after pregnancy, using immunofluorescence staining and fluorescence-activated cell sorting analysis
Results: The clinical and immunologic follow-up data from 42 pregnant patients with MS indicated that the percentage of circulating NK cells decreases during the last trimester of pregnancy and increases again soon after the delivery. This correlates with disease activity as measured by annualized relapse rate. Early postpartum treatment with interferon-0 was effective in preventing relapses, and good response to postpartum treatment coincided with a reduction in the circulating NK cell levels.
Conclusions: Our findings have implications for the treatment and follow-up of pregnant women with MS. To prevent postpartum relapses, disease-modifying treatment should be initiated as early as possible.