Abstract Background/Introduction Maternal hyperthyroidism, that affects 0.1% to 0.4% of pregnancies, has been/is associated with adverse pregnancy outcomes, including preterm birth, fetal growth restriction, and neonatal complications. Maternal thyroid disease has been linked to an increased risk of congenital heart defects (CHDs) in the offspring, however, the relationship between maternal hyperthyroidism and structural and functional cardiac abnormalities in newborns remains unclear. Purpose This study aimed to evaluate the association between maternal hyperthyroidism during pregnancy and risk of altered cardiac structure and function in newborns. Methods In this study, we included neonatal echocardiographic data from a prospective, population-based multicenter cohort study of prenatally enrolled newborns. The participants underwent echocardiography within 60 days of birth. Maternal hyperthyroidism diagnoses were identified via the Danish national health registries and validated by medical journal review. Outcomes were echocardiographic measurements of left and right ventricular dimensions and function, atrial size, aortic and pulmonary artery dimensions, valve metrics, and assessment of CHDs. Structural CHDs were classified as minor or moderate-severe, based on established criteria from Hoffman and Kaplan. We compared echocardiographic findings from newborns of mothers with hyperthyroidism to unexposed newborns using regression analyses. Results A total of 25,592 newborns were included in the study, of which 212 newborns were born to mothers with a validated diagnosis of maternal hyperthyroidism. Infants exposed to maternal hyperthyroidism had a thicker interventricular septum in end-diastole (adjusted mean difference aMD ± standard error 0.1 (±0.03) mm, p=0.002) and smaller diameter of the ascending aorta (aMD -0.3 (±0.2) mm, p=0.045) compared to unexposed infants. Other dimensions and functions of the left and right ventricles and atria, aortic, main pulmonary artery and valve measurements were similar between the two groups. There were no significant associations between maternal hyperthyroidism and increased risk of minor or major CHDs in the newborns. Conclusions Maternal hyperthyroidism was associated with a subtle thickening of the interventricular septum and a smaller diameter of the ascending aorta in newborns. These findings suggest that maternal hyperthyroidism, most likely well-managed in many cases, may only have subtle effects on cardiac morphology in the newborn with subclinical implication. Follow-up is needed to determine whether these changes persist, and to explore their potential long-term implications.
Vollmond et al. (Sat,) studied this question.