If I take methimazole will it harm my baby?

Yes, it may cause harm to the baby. Methimazole is not recommended during pregnancy. It has been assigned to pregnancy Category D by the FDA, which means that there is strong evidence that it can harm your baby if you take it during pregnancy.

Methimazole can cross the placenta and enter the fetus's bloodstream to cause goiter and hypothyroidism after the infant is born, which are risk factors for mental retardation. The goiter could get large enough to block the infant's airway and cause breathing problems. On rare occasions methimazole during pregnancy can cause congenital defects of the scalp, esophagus, trachea, nose and nipples. Pregnant women should take other medicines for hyperthyroidism.

Sometimes when a woman with hyperactive thyroid disease becomes pregnant, her thyroid hormone levels change for the better, so it is possible that methimazole may not be needed. However, if you are planning on becoming pregnant discuss alternate treatment options beforehand. If you discover you are pregnant while you are taking it, notify your doctor as soon as possible.

Nursing is also not recommended, but if you are taking less than 20 mg./day you can minimize the amount your baby gets if you take methimazole when you are done nursing and wait for three to four hours before nursing again. This way your baby gets the least amount possible.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.