Safety of breastfeeding under monoclonal antibodies in the offspring of mothers with multiple sclerosis or neuromyelitis optica spectrum disorder

BACKGROUND: Women with multiple sclerosis (MS) or neuromyelitis optica spectrum disorder (NMOSD) and highly active disease may benefit from early post partum reinitiation of disease-modifying therapy (DMT), but safety data to monoclonal antibody (mAb) use while breastfeeding are limited. This study examined infant development and health following potential mAb exposure during breastfeeding. METHODS: A prospective monocentric cohort study of infants, born in 2013-2022, in the German MS and Pregnancy Registry, followed up 6-36 months post partum via telephone interviews. 183 infants breastfed during maternal mAb therapy (mAb use during breastfeeding (mAb-BF)) were matched 1:1 (DMT pregnancy exposure) to infants of DMT-naïve mothers (no-DMT-BF). Primary outcomes included developmental delay, systemic antibiotic use, hospitalisation, severe infection and growth. Adjusted regression models estimated the beta coefficient, OR or rate ratio with 95% CI. RESULTS: The study included 366 infants. Among 183 mAb-BF infants, most were breastfed on natalizumab (n=125), followed by ocrelizumab (n=34), rituximab (n=11) and ofatumumab (n=10); three had multiple exposures. Developmental delays occurred in 8.2% mAb-BF and in 7.1% no-DMT-BF infants (p=0.844). A comparable number of infants used a systemic antibiotic (n=33/183, 18.0% vs n=29/183, 15.8%; p=0.676), were hospitalised (n=18/183, 9.8% vs 19/183, 10.4%; p=1.000) or had a severe infection (n=14/183, 7.7% vs n=13/183, 7.1%; p=1.000). The physical growth and adjusted model outcomes were also similar. CONCLUSIONS: The results indicate that infants of mothers with neuroimmunological diseases, breastfed under mAbs, did not experience negative consequences for their development and health within the initial 6-36 months of life. This may encourage mothers with highly active disease to breastfeed.