Treatment with high-dose estrogens has been used to reduce the adult height of tall girls for many years. Short-term side effects on the breast have been reported but there have been no studies to investigate whether there are long-term effects on lactation. This retrospective cohort study of 371 treated and 409 untreated women asked about breastfeeding history. After adjusting for maternal age at first live-birth, treated women (4.4%) were no more likely than untreated women (4.1%) to not commence breastfeeding (RR 1.13, 95% CI 0.50–2.52). After adjusting for age, there was no significant difference in the average duration of breastfeeding between treated (median 41.1 weeks) and untreated women (median 43.3 weeks) (p = 0.77) for all live-births. Treated women were not significantly more likely to report physiological reasons for stopping breastfeeding than untreated women. Women treated with high-dose estrogens during adolescence appeared to be no different to untreated women in their ability to lactate.