Interferon-betas (IFN-β) are cytokines, glatiramer acetate (GA) is a synthetic polypeptide. Both substances are large molecules and lack oral bioavailability. As of September 2019, IFN-β are the first and up to now the only multiple sclerosis (MS) therapy approved also during lactation. Published data are restricted but show only minimal concentrations of the drug in human milk. No data on GA excretion are available, but it seems unlikely the substance would pass into breast milk. Although the risk for the infant is most likely negligible, data on breastfeeding under IFN-β or GA are very restricted. The effects on infant development and health as well as on maternal relapse risk postpartum are yet unknown.
To assess the safety of maternal IFN-β 1a or GA administration during lactation for the breastfed infant as well as to assess its effect on the occurrence of postpartum relapses.
So far, we identified 34 infants (one pair of twins) who were breastfed under GA and 28 infants who were breastfed under IFN-β 1a from the German MS and pregnancy registry (DMSKW). Cases were followed-up for at least one year postpartum. Data was generated via standardized interviews, conducted with the mother during pregnancy as well as at 1, 3, 6 and 12 months postpartum.
Identification, inclusion and follow-up of additional cases are still ongoing; updated data as well as analysis of the total cohorts will be presented at the congress. Among the infants breastfed under GA there was no case of developmental delay, in the IFN-β 1a cohort there was one report of a delay regarding motor skills (4 %). Medians of weight, length and head circumference at several medical check-ups during the first year of life lay within the normal range (3rd and 97th percentile) of reference values for both cohorts. Hospitalizations and antibiotic treatments occurred only rarely. Within the first year postpartum 7 (21 %) women relapsed in the GA cohort as well as 7 (25 %) in the IFN-β 1a cohort.
Our preliminary analysis revealed no hints that treatment with GA or IFN-β 1a during lactation negatively affects development or health of breastfed infants. The effect on postpartum relapses has still to be determined. Our results support the recent label extension of IFN-β and suggest that treatment with GA is probably compatible with breastfeeding as well.