[Effects of maternal hyperthyroidism and antithyroid drug therapy on congenital malformation of newborn infants]

Abstract

Objective: To evaluate the relationship between the incidence of congenital malformations of newborns and maternal hyperthyroidism with antithyroid drug (ATD) therapy during pregnancy.

Methods: The clinical data of 100 cases of pregnant women with hyperthyroidism and their 101 offsprings born in Peking Union Medical College Hospital during 1983-2003 were analyzed retrospectively. According to the maternal thyroid function, and antithyroid drugs taken during the first trimester of pregnancy, subjects were divided into different groups. The incidence of congenital malformations of newborns and risk factors, especially the effects of maternal hyperthyroidism with antithyroid drug therapy were analysed.

Results: The prevalence of congenital malformation in infants born to mothers who had hyperthyroidism during pregnancy (6.9%, 7/101) was significantly higher than that of all the infants born in the same hospital during the same period (0.9%, 212/22 765, P < 0.01). The difference of the incidence of malformed infants born to mothers with hyperthyroidism (9.6%, 5/52) or euthyroidism (4.1%, 2/49) during the first trimester was not significant (P > 0.05). The incidence of malformed infants whose mothers received methimazole (MMI; 41.7%, 5/12) was significantly higher than that of mothers treated with propylthiouracil (PTU) (3.6%, 1/28) and without ATDs (1.6%, 1/61), respectively (P < 0.01). The Loglinear model analyses showed that mothers receiving MMI during the first trimester of pregnancy was independent risk factor for the increased incidence of malformation of their infants (L.R. square = 15.668, P = 0.0003).

Conclusions: The risk of congenital malformation in infants whose mothers take MMI during the first trimester may be increased. Therefore, we suggest that MMI should not be used as a choice of drug in treatment of pregnant women with hyperthyroidism.