Safety of potential breast milk exposure to IFN-β or glatiramer acetate: One-year infant outcomes

To determine whether potential breast milk exposure to interferon-beta (IFN-β) or glatiramer acetate (GA) is safe for the infant. We identified 74 infants born to 69 women with MS who breastfed under IFN-β (n = 39), GA (n = 34), or both (n = 1). Women had been enrolled into the German Multiple Sclerosis and Pregnancy Registry during pregnancy. Data were obtained from standardized, telephone-administered questionnaires completed by the mother during pregnancy and at 1, 3, 6, and 12 months postpartum and the infant's take-home medical record. The median duration of exposed breastfeeding was 8.5 months (wide interquartile range: 4.9-12.7 months). Physical growth curves during the first year of life were consistent with national, sex-specific growth curves. Median body measurements were consistent with national medians. Most children (n = 71, 96%) had normal motor and language development. Gross motor delay was reported in 3 children, of whom 1 remained delayed at last follow-up (3.9 years old) and 2 were normal by 0.9 and 4.1 years old. The proportion of children hospitalized at least once (girls n = 2, 7%, and boys n = 6, 14%) and the proportion of children with at least one episode of systemic antibiotic use during the first year of life (girls n = 7, 23%, and boys n = 8, 18%) are consistent with national averages. Potential breast milk exposure to IFN-β or GA did not increase the risk of common adverse infant outcomes in the first year of life. Taken together with the benefits of breastfeeding and low biological plausibility of risk, women with MS who wish to resume IFN-β or GA postpartum can be encouraged to breastfeed.