Birth defects linked to antithyroid drug treatment in pregnancy

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Birth defects linked to antithyroid drug treatment in pregnancy have for a long time been known to exist. A recent Danish register-based cohort study has assessed the degree of association of antithyroid drugs (ATD), such as methimazole (MMI) / carbimazole (CMZ) and propylthiouracil (PTU), and the spectrum of disease.

Epidemiology

The prevalence of birth defects appears to be high in children exposed to ATD in early pregnancy. Both MMI/CMZ and PTU are associated with an increased odds ratio of birth defects, with an odds ratio (OR) approximating 2. The commonest defects in MMI/CMZ-exposed children seem to appear with an adjusted OR ~20 when combined .

Clinical presentation

MMI/CMZ-exposed children may commonly develop:

choanal atresia
esophageal atresia
omphalocele
omphalomesenteric duct anomalies
aplasia cutis

Both MMI/CMZ and PTU have been shown to be associated with urinary system malformation. Moreover, PTU may predominantly cause malformations in the face and neck region.

Pathology

Hyperthyroidism in pregnant women is a known source of a variety of maternal and fetal complications, necessitating the use of antithyroid drug treatment (ATD) in pregnancy to control maternal hormone levels.