Objective: To evaluate maternal and breastfed infant’s outcome following post-partum maternal use of methylergonovine. Methods: A prospective, controlled observational study design was used. Mothers who contacted Beilinson Teratology Information Service (BELTIS) were followed by phone interview. Data on lactation, neonatal symptoms and outcomes at the age of 1–3 years were obtained. Mothers’ breastfeeding while treated with methylergonovine and their infants were compared to a matched control group of breastfeeding mothers using a drug known to be safe during lactation (amoxicillin). Results: Follow-up was obtained for 38 of 42 women (90.5%). Of whom, six stopped breastfeeding because of concerns regarding drug treatment and three refused to participate. The remaining 29 women and infant pairs were compared to a control group of 58 women and their infants. Comparison showed no effect of methylergonovine on lactation and similarly showed no difference in rate of neonatal complications (p = 1). At time of follow-up there were no differences in growth or in adverse neurodevelopment outcomes (p = 0.26). Conclusions: No increase in adverse long-term outcomes was found in infants exposed to methylergonovine through breastfeeding. Our data in conjunction with previous estimates of very low drug exposure support continuation of breastfeeding in women requiring treatment with methylergonovine.