Use in pregnancy: From observations in man, it has become apparent that thiamazole can be harmful to the fetus. In particular, there have been a number of reports of the appearance of aplasia cutis of the skull. The evidence of teratogenicity is as yet, too weak to contraindicate use during pregnancy. Strumazol should only be used in pregnancy upon consultation with a specialist.
In prescribing anti-thyroids, it must be borne in mind that all thyroid depressants cross the placenta and therefore can lead to hypothyroidism and goiter formation in the fetus. In Graves' disease, one must also be prepared for the onset of hyperthyroidism in the fetus and thus, it would be advisable to treat the patient on anti-thyroid.
Use in lactation: The use of the standard dose of Strumazol leads to significant quantities of thiamazole in the mother's milk. Propylthiouracil is then preferable. Strumazol should only be used during lactation in consultation with a specialist.