Maternal hypothyroidism may affect fetal growth and neonatal thyroid function.

Area of Science:

• Neonatal endocrinology
• Maternal-fetal medicine
• Thyroid disease management

Background:

• Maternal hypothyroidism requires careful management during pregnancy to ensure optimal fetal development.
• The pituitary-thyroid axis in neonates born to treated hypothyroid mothers requires investigation.
• Assessing the adequacy of maternal thyroid hormone replacement therapy is critical.

Observation:

• Newborns of treated hypothyroid mothers exhibited elevated serum thyroid-stimulating hormone (TSH) and free thyroxine (T4) levels.
• A significant proportion of these neonates displayed TSH and free T4 levels above the 95th percentile of controls.
• Impaired intrauterine growth, evidenced by lower birth weight and head circumference, was observed in the study group.

Findings:

• Neonatal TSH and free T4 levels were significantly higher in infants of treated hypothyroid mothers compared to controls.
• The correlation between neonatal TSH and free T4 differed between study infants and controls.
• Maternal TSH during pregnancy positively correlated with neonatal TSH in a subset of cases.

Implications:

• Elevated neonatal TSH and free T4, alongside impaired growth, may indicate insufficient maternal thyroid hormone levels during gestation.
• Current management protocols for maternal hypothyroidism during pregnancy may require re-evaluation.
• Enhanced monitoring of pregnant individuals with hypothyroidism is recommended to optimize neonatal outcomes.