Possible association between hyperthyroidism in pregnant women and obstructive congenital abnormalities of urinary tract in their offspring – a population-based case–control study

Abstract

Objective. The teratogenic potential of some antithyroid drugs is known, but the aim of the study was to estimate the risk of congenital abnormalities (CAs) in the offspring of pregnant women with hyperthyroidism with or without antithyroid drug treatment.

Method. Comparison of the occurrence of medically recorded hyperthyroidism who had malformed fetuses/newborns (cases) and who delivered healthy babies (controls) in the population-based Hungarian Case–Control Surveillance System of CAs, 1980–1996. Of 22,843 cases with congenital abnormalities, 71 (0.31%) while of 38,151 controls, 116 (0.30%) had mothers with hyperthyroidism. The rate of hyperthyroidism in the mothers of cases with different CAs and in the mothers of matched controls was compared.

Results. Preeclampsia–eclampsia occurred more frequently in pregnant women with hyperthyroidism without antithyroid treatment. The analysis of specific groups of CAs showed an association between hyperthyroidism in pregnant women and obstructive defects of urinary tract in their children.

Conclusions. The lack of appropriate treatment of pregnant women affected with hyperthyroidism seems to be the major problem, because it would be necessary to prevent the hyperthyroidism related risks of pregnancy complications and CAs which exceed the risk of antithyroid medication in these pregnant women.

Keywords:

• Hyperthyroidism
• pregnancy
• antithyroid drugs
• pregnancy complications
• congenital abnormalities
• obstructive defects of urinary tract
• case–control study

Acknowledgements

This study was partly sponsored by a generous grant from Richter Gedeon Pharmaceuticals Ltd., Budapest, Hungary.