Impact of Maternal Obesity on Neonatal TSH Levels: A Prospective Study on the Influence of BMI

Thyroid hormones are crucial for fetal growth, especially the development of the central nervous system. The impact of maternal obesity on neonatal thyroid-stimulating hormone (TSH) levels, however, remains underexplored. This study aimed to evaluate the influence of maternal body mass index (BMI) on neonatal TSH (nTSH) levels. A prospective observational study was conducted involving 934 newborns with a gestational age greater than 35 weeks, born between July 2021 and January 2022. nTSH levels were measured from capillary blood samples obtained during routine congenital hypothyroidism screening. Maternal data, including age, pre-pregnancy BMI, weight gain during pregnancy, and thyroid function, were collected. The mean maternal BMI was 24 ± 4 kg/m2, and the mean nTSH level was 2 ± 2.7 mIU/L. No significant difference in nTSH levels was observed between infants of mothers with BMI ≥25 and BMI <25 (p = 0.069). When mothers were categorized into five BMI groups, the only significant difference observed between the groups was in weight gain during pregnancy (p = 0.001). Additionally, a positive correlation between maternal BMI and neonatal birth weight, height, and head circumference was observed. A weak positive correlation between maternal weight gain and nTSH levels (r = 0.204, p = 0.001) was also noted. Our study indicates a potential relationship between maternal obesity and nTSH levels, suggesting that maternal BMI may influence neonatal thyroid function.