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Selections from Journal Watch Pediatrics and Adolescent Medicine Copyright © 2005 Massachusetts Medical Society. All rights reserved.
Treatment of maternal hyperthyroidism can be problematic in some pregnancies ▸
In an estimated 0.2% of pregnancies, women have thyrotoxicosis that requires therapy. The most commonly used antithyroid drugs cross the placenta, and reports of possible teratogenic effects of methimazole (MZ) and carbimazole (CZ) have been appearing since the 1970s. In this case report and literature review, the authors ask whether a rare phenotype is associated with prenatal CZ exposure.
The authors report the cases of two children with in utero exposure to CZ and remarkably similar, distinctive clinical presentations: short, upslanting palpebral features, small nose with broad nasal bridge, and broad forehead. Aplasia cutis of the scalp; GI tract anomalies (including imperforate anus, esophageal atresia, omphalocele, and bilateral choanal atresia); hypoplastic nipples and breasts; a variety of congenital heart defects; developmental delay; and hearing loss have also been reported after in utero exposure to MZ and CZ. The authors note the importance of controlling maternal thyroid function before and during pregnancy to prevent fetal loss, low birth weight, preterm labor, hydrops, fetal goiter, and newborn craniosynostosis. They also point out that the frequency of CZ/MZ-associated complications is unknown and that infant outcomes in most such pregnancies are good.
As with many other drugs, a genetic susceptibility must be present in the mother, the infant, or both for the teratogenic effects to occur. Pediatricians should be aware of the features of methimazole and carbimazole complications and ask …
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