TOPLINE:

Maternal thyroid function or the status of common thyroid autoantibodies during early pregnancy was not associated with an increased risk for birth defects in children; however, positivity for thyroid-stimulating autoantibodies was associated with a higher risk.

METHODOLOGY:

• Researchers in Denmark conducted a retrospective cohort study to evaluate the association between maternal thyroid function, thyroid autoantibodies, and the risk for birth defects.
• They analysed data of 20,399 pregnant women with no known thyroid disease and their singleton live-born children by using information from national registries.
• Blood samples were collected during early pregnancy for the assessment of maternal thyroid function and autoantibodies.
• Researchers assessed levels of thyroid-stimulating hormone (TSH); free thyroxine (fT4); and thyroid autoantibodies such as thyroid peroxidase antibodies (TPO-Abs), thyroglobulin antibodies (Tg-Abs), TSH receptor antibodies (TRAbs), and thyroid-stimulating immunoglobulin (TSI); maternal thyroid function was classified on the basis of whether TSH levels were within the cohort-specific reference interval or outside it.
• Birth defect outcomes were ascertained from national registers, with diagnoses included up to the age of 2 years.

TAKEAWAY:

• Overall, 702 (3.4%) children had birth defects. Maternal TSH and fT4 levels did not differ between children with and without birth defects.
• No significant difference in the prevalence of birth defects was observed between children born to mothers who were negative and positive for TPO-Abs or Tg-Abs.
• Children born to mothers positive for TRAbs and/or TSI showed a higher prevalence of birth defects (adjusted odds ratio, 3.5; 95% CI, 1.4-8.6), with the association being more prominent for TSI positivity.
• Among seven children with birth defects exposed to maternal TSI, most (four) had cardiac malformations.

IN PRACTICE:

"The findings inform clinical practice regarding risks and recommendations for treatment of the hyperthyroidism of GD [Graves disease] in pregnant women," the authors wrote.

SOURCE:

This study was led by Stine Linding Andersen, MD, PhD, DMSc, Department of Clinical Biochemistry, Aalborg University Hospital, Aalborg, Denmark. It was published online on February 04, 2026, in The Journal of Clinical Endocrinology & Metabolism.

LIMITATIONS:

TSH levels were measured only once during early pregnancy, which may not have reflected consistent thyroid function abnormalities and actual thyroid disease. The study primarily included pregnant women with normal thyroid function, and a significant number of women with TSH levels below the lower reference interval likely had gestational transient thyrotoxicosis rather than hyperthyroidism due to Graves disease.

DISCLOSURES:

The research was conducted using the Danish National Biobank resource and was financially supported by the Novo Nordisk Foundation. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.