Birth defects observed with maternal carbimazole treatment: Six cases reported to Nice's Pharmacovigilance Center

To report cases of embryopathy occurring following first trimester exposure to anti-thyroid drugs.

Retrospective screening of the database of our Pharmacovigilance Center from 1987 to date.

We report six cases of embryopathy, all following carbimazole exposure during the first trimester: two cases of abdominal wall defect, including one associated with facial dysmorphia; one case of digestive malformation (patent omphalomesenteric duct); two cases of aplasia cutis including one with facial dysmorphism; one case of bilateral choanal atresia with aorta coarctation associated with poorly controlled insulin dependent diabetes. Four out of five patients were euthyroid with treatment during the first trimester. We found a context suggesting genetic predisposition to congenital malformation in three cases: two cases of parental cleft lip/palate, one case of consanguinity. Outcome was favorable in all cases.

We want to raise awareness about the potential teratogenicity of carbimazole, probably on a predisposed genetic background. We suggest better reporting of congenital anomalies in children of women with Graves'disease, with or without in utero exposure to anti-thyroid drugs. In light of current literature, propylthiouracil should be the first line treatment for hyperthyroid women wishing a pregnancy.