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Carbimazole embryopathy in a Chinese population: Case series and literature review


Correspondence to: Prof. Terence T. Lao, Department of Obstetrics and Gynaecology, Prince of Wales Hospital, Shatin, New Territories, Shatin, Hong Kong. E-mail:



The data in the literature suggests that Methimazole (MMI)/Carbimazole (CMZ) embryopathy is rare. This study examined the incidence of CMZ embryopathy in the Hong Kong Chinese population and the factors associated with its development.


Of the 145 pregnant women with hyperthyroidism managed from 2008 to 2010, 29 (20%) had taken CMZ during pregnancy. The presence and details of birth defects, the dosage of CMZ, and the period of exposure during pregnancy were examined in these 29 pregnancies. All cases of CMZ embryopathy in the English literature were reviewed in the same way.


Of the 27 babies (93.1%) with known outcome, 3 had aplasia cutis and 1 had an omphalocele in addition, and 1 affected baby had a sibling with aplasia cutis and patent vitellointestinal duct. The incidence of CMZ embryopathy in our study group is 11.1%. Amongst the 21 cases of CMZ embryopathy in the literature, 85% were exposed to a CMZ dosage of ≥20 mg/day, and the minimum duration of exposure being 7 weeks from last menstrual period. The most common abnormality is ectodermal anomaly (62%), followed by oro-nasal anomaly (48%), facial dysmorphism (38%), gastrointestinal anomaly (33%) and abdominal wall defect (19%). There was no relationship between the type of abnormality and the dosage or duration of exposure to CMZ.


The incidence of CMZ embryopathy in our study group is 11.1%. Critical factors for its development are exposure to a CMZ dosage of ≥20 mg/day before 7 weeks of gestation. Genetic susceptibility may also play a role. Birth Defects Research (Part A) 97:225–229, 2013. © 2013 Wiley Periodicals, Inc.

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