Thyrotoxicosis in pregnancy: results of treatment by antithyroid drugs combined with T4.

Treatment of thyrotoxicosis in pregnancy with antithyroid drugs plus supplementary T4 is controversial. Data are presented on twenty consecutive pregnancies treated by this method. The mean birth weights of the babies and their gestation did not differ from those of normal controls. Cord blood mean T4 and free T4 index (FT4I) were not significantly different from controls and total T3 and free T3 index (FT3I), though significantly lower than the controls, were all within the normal range. In five babies in whom they were measured, FT3, FT4 and rT3 levels were not significantly different from controls. Cord TSH was significantly higher in the babies of thyrotoxic mothers than in the control babies. One baby had a goitre at birth which disappeared after a few days. Another baby, born euthyroid, developed neonatal thyrotoxicosis the day after birth. Data collected from the literature on this method of treatment are compared with similar data from women treated with antithyroid drugs alone.