Infant adverse reactions to drugs in human milk reported to the Danish Medicines Agency from 2013 to 2023

SummaryMany breastfeeding women take medications, potentially exposing their infants to adverse drug reactions (ADRs) through human milk. This study aimed to describe suspected ADRs in infants due to medication transmitted via breastfeeding. Using an observational cohort design, we analyzed spontaneous reports submitted to the Danish Medicines Agency from July 2013 to June 2023, as recorded in the National Danish Adverse Drug Reaction Database. ADRs indicate suspected, not proven, associations between medications and adverse outcomes. In total, 64 ADRs were reported in breastfed infants: 53% were girls, 39% boys, and 8% with unreported sex, with over half aged between 1 month and 1 year. Serious ADRs occurred in 28% of cases, while 72% were nonserious. No fatalities were recorded. The most frequently reported reactions involved general disorders, gastrointestinal issues, skin disorders, and metabolic or nutritional disturbances. COVID-19 vaccines were the most frequently reported drugs. The low number of reports may reflect underreporting or a low incidence of ADRs, underscoring the need for further research and increased awareness.