To examine the gap between the current social/medical practice and the evidence-based recommendation in favor of breastfeeding during maternal propylthiouracil (PTU) therapy.


Prospective, observational, cohort study.


Women requiring PTU during pregnancy, and endocrinologists and family physicians in Ontario, Canada.



Main Outcome Measures.

Women were interviewed postpartum regarding their choice of infant feeding method and relevant advice received from physicians. Physicians were questioned about their advice to nursing women receiving PTU.


Of 78 women, 66 had live births. Thirty-six required PTU postpartum (group 1), and 30 did not (group 2). Thirty-six healthy women served as controls (group 3). Breastfeeding initiation rates for groups 1, 2, and 3 were 44%, 83%, and 83%, respectively. In group 1, 15 women who breastfed received advice from 22 physicians regarding breastfeeding (20 in favor, 1 against, and 1 equivocal). Eleven who formula fed received advice from 17 physicians (4 in favor, 12 against, and 1 equivocal). A logistic regression analysis of group 1 showed that physicians' advice was the only significant predictor of the woman's choice to breastfeed during PTU therapy (relative risk: 5.48; 95% confidence interval: 1.28–23.40). The physician survey showed that 44% of endocrinologists do not recommend breastfeeding during PTU therapy.


A substantial proportion of the lactating patients on PTU still receive advice against breastfeeding from their physicians. Physicians' advice and attitudes toward breastfeeding during PTU therapy are a major factor in women's final decision to breastfeed. Physicians' compliance with evidence-based data will facilitate breastfeeding in this group. propylthiouracil, breastfeeding, decision-making.

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