Pregnancy-related relapses and breastfeeding in a contemporary multiple sclerosis cohort

Objective To determine whether women with multiple sclerosis (MS) diagnosed according to current criteria are at an increased risk of postpartum relapses and to assess whether this risk is modified by breastfeeding or MS disease-modifying therapies (DMTs), we examined the electronic health records (EHRs) of 466 pregnancies among 375 women with MS and their infants. Methods We used prospectively collected information from the EHR at Kaiser Permanente Southern and Northern California between 2008 and 2016 of the mother and infant to identify treatment history, breastfeeding, and relapses. Multivariable models accounting for measures of disease severity were used. Results In the postpartum year, 26.4% relapsed, 87% breastfed, 36% breastfed exclusively for at least 2 months, and 58.8% did not use DMTs. At pregnancy onset, 67.2% had suboptimally controlled disease. Annualized relapse rates (ARRs) declined from 0.37 before pregnancy to 0.14-0.07 (p < 0.0001) during pregnancy, but in the postpartum period, we did not observe any rebound disease activity. The ARR was 0.27 in the first 3 months postpartum, returning to prepregnancy rates at 4-6 months (0.37). Exclusive breastfeeding reduced the risk of early postpartum relapses (adjusted hazard ratio = 0.37, p = 0.009), measures of disease severity increased the risk, and resuming modestly effective DMTs had no effect (time-dependent covariate, p = 0.62). Conclusion Most women diagnosed with MS today can have children without incurring an increased risk of relapses. Women with suboptimal disease control before pregnancy may benefit from highly effective DMTs that are compatible with pregnancy and lactation. Women with MS should be encouraged to breastfeed exclusively.