Pregnancy and fetal outcomes after interferon-β exposure in multiple sclerosis.

OBJECTIVE: To assess pregnancy and fetal outcomes after in utero exposure to interferon-β (IFNβ) in all pregnancies occurring in women with multiple sclerosis (MS) during the study period, with a specific focus on the risk of spontaneous abortion. METHODS: In this cohort study, data were gathered through a standardized, semi-structured interview. Patients who discontinued IFNβ less than 4 weeks from conception (exposed) were compared with those who had discontinued the drug at least 4 weeks from conception or who were never treated (not exposed). Possible confounders were handled through multivariate analyses adjusted for propensity score (PS). RESULTS: We collected data on 396 pregnancies in 388 women, 88 classified as exposed (mean exposure 4.6 ± 5.8 weeks). IFNβ exposure was not associated with an increased risk of spontaneous abortion (PS-adjusted odds ratio [OR] 1.08, 95% confidence interval [CI] 0.4 to 2.9, p = 0.88), although it was associated with both lower baby weight (PS-adjusted β -113.8, p < 0.0001) and length (PS-adjusted β -1.102, p < 0.0001). Proportion of spontaneous abortion in exposed patients fell within the range expected for the Italian population in the same period. IFNβ exposure (PS-adjusted OR 2.11, 95% CI 1.18 to 3.78, p = 0.012) and cesarean delivery were the only predictors of preterm delivery. In the exposed group, we did not observe any significant fetal complications, malformations, or developmental abnormalities over a median follow-up of 2.1 years. CONCLUSIONS: Our findings point to the relative safety of IFNβ exposure times of up to 4 weeks and can assist neurologists facing therapeutic decisions in women with MS with a pregnancy plan.