Maternal thyroid dysfunction during pregnancy increases risk for thyroid disease, type 1 diabetes, and schizophrenia, according to a study summary recently published in Clinical Thyroidology. Maternal Graves disease and Hashimoto disease during pregnancy increases childhood risk for type 1 diabetes and schizophrenia, respectively.  

The researchers conducted a large-scale, nationwide cohort study including data from 1,560,955 children, 2618 of whom were exposed to maternal Graves disease in utero and 760 of whom were exposed to maternal autoimmune hypothyroidism. The proportion of children exposed to Hashimoto disease increased over the study period. The proportion of children exposed to Graves disease remained constant. Cesarean sections were more common in women with thyroid disease (24% in Graves and 26% in Hashimoto) than without (15%). 

Maternal Graves disease during pregnancy was associated with greater risks for childhood thyroid disease (hazard ratio [HR], 12.83; 95% CI, 9.74-16.90), Graves disease (HR, 34.33; 95% CI, 20.23-58.25), and type 1 diabetes (HR, 2.47; 95% CI, 1.46-4.18). Maternal Hashimoto disease during pregnancy was associated with greater risk for childhood thyroid disease (HR, 11.12; 95% CI, 5.53-22.34), Hashimoto thyroiditis (HR, 24.02; 95% CI 5.89-97.94), and schizophrenia (HR, 10.64; 95% CI, 92.80-40.41). 

Limitations of this study include the lack of thyroid function testing in mothers, the lack of information regarding maternal thyroid medications, the relatively small number of outcomes assessed, and the use of International Classification of Disease coding to define maternal thyroid disease. Additionally, Hashimoto thyroiditis should have been more prevalent than Graves, so it is possible that there were missed cases of Hashimoto disease. Additionally, children of women with diagnosed thyroid disorders may have undergone thyroid function testing as part of routine care, unlike most children.

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The association between women with thyroid autoimmunity and childhood predisposition for autoimmune thyroid and other autoimmune disorders is not surprising. Autoimmune disorders are known to exhibit strong genetic components. However, the association between hypothyroidism and schizophrenia is surprising and requires further research. Long-term follow-up studies including large cohorts of children with chronic disease related to maternal thyroid function in pregnancy are necessary to further understand the role of genetics and/or the gestational thyroid hormone milieu. 

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Reference

Pearce EN. Maternal thyroid function during pregnancy is associated with increased childhood risk for thyroid disease, type 1 diabetes, and schizophreniaClin Thyroidol. 2018;30:560-562.