Thyroid hormones are crucial developmental factors and thyroid disease in pregnant women is a concern. Overweight and obesity are also important health concerns, and we hypothesized that in utero exposure to maternal thyroid disease could program the fetus to development of adiposity.
Cohort and case-cohort studies PARTICIPANTS: Pregnant women from the Danish National Birth Cohort and their 7-year old children.
Maternal thyroid disease (hyperthyroidism and hypothyroidism) was assessed from registrations of diagnoses and treatment (n = 71,706) or from the measurement of thyroid-stimulating hormone (TSH) in a stored blood sample from the early pregnancy (n = 7,624). Maternal pre-pregnancy body mass index (BMI) and child BMI at 7 years of age were used to define overweight and obesity, and associations were evaluated using regression models adjusting for potential confounders.
No association was found between maternal thyroid disease in pregnancy and child overweight (hyperthyroidism: adjusted risk ratio (aRR): 1.02 (95% confidence interval (CI): 0.58-1.82); hypothyroidism: 1.31 (0.86-1.97)) or obesity (hyperthyroidism: 0.96 (0.53-1.75); hypothyroidism: 1.25 (0.76-2.05)). On the other hand, pregnant women with hypothyroidism in early pregnancy had a higher risk of being overweight (aRR: 1.20 (95% CI: 1.03; 1.41)) and obese (1.45 (1.07; 1.96)), whereas women with hyperthyroidism had a lower risk of being overweight (0.79 (0.64; 0.98)).
Results provide no evidence that maternal thyroid disease in pregnancy programs adiposity in the child, but corroborate an association between maternal thyroid disease and adiposity in the mother.

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