Monoclonal antibody treatment during pregnancy and/or lactation in women with MS or neuromyelitis optica spectrum disorder

Objective To assess possible adverse effects on breastfed infants of mothers receiving monoclonal antibodies (MAbs) during pregnancy and/or lactation. Methods We identified 23 patients from the German Multiple Sclerosis and Pregnancy Registry (DMSKW) who received MAbs (17 natalizumab and 6 anti-CD20) during lactation. Thirteen were already exposed to natalizumab during the third trimester of pregnancy, and 1 received ocrelizumab 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. Natalizumab concentration in mother's milk was analyzed in 3 patients and natalizumab serum concentration in 2 of these patients and their breastfed infants. Results We did not observe a negative impact on infant health and development attributable to breast milk exposure after a median follow-up of 1 year. Infants exposed to natalizumab during the third trimester had a lower birth weight and more hospitalizations in the first year of life. The concentration of natalizumab in breast milk and serum of infants was low; B cells normal in infants breastfed under anti-CD20. Conclusion More data on the effect of Mab exposure during pregnancy are needed. Otherwise, our data suggest that treatment with natalizumab, ocrelizumab, or rituximab during lactation might be safe for breastfed infants.