Thyroid Profile of Neonates Born to Mothers with Hypothyroidism Detected Before and During Pregnancy

Introduction: Congenital hypothyroidism is a leading preventable cause of intellectual disability. This study explores whether maternal hypothyroidism provides a greater risk for congenital hypothyroidism and compares thyroid hormone levels in infants born to mothers with pregestational versus gestational hypothyroidism. Methodology: In an 18-month prospective cohort study at a medical college, 102 newborns from mothers on hypothyroidism treatment were assessed. Infants were divided into two groups: those born to mothers with gestational hypothyroidism (Group 1) and those with pregestational hypothyroidism (Group 2). Newborns were screened for congenital hypothyroidism using cord TSH levels at birth, followed by venous TSH and free T4 measurements at 2-7 days and 2-6 weeks. Statistical analyses included t-tests, Chi-square tests, and ANOVA with p<0.05 considered significant. Results: The cohort included 102 infants with a near 1:1 male-to-female ratio and a mean birth weight of 2.809 kg. Fifty-seven percent of mothers had pregestational hypothyroidism and 43% had gestational hypothyroidism. The mean cord TSH was 9.4 mIU/L, with 18 infants showing elevated levels. Four infants had elevated serum TSH at 48 hours, and seven had elevated TSH at 2-6 weeks. Free T4 levels averaged 3.14 ng/dL at 2-7 days and 1.82 ng/dL at 2-6 weeks. No significant differences were found between groups. Subclinical hypothyroidism was noted in 4 infants, with no cases of overt hypothyroidism. Conclusion: Infants of mothers with adequately treated hypothyroidism generally have normal thyroid hormone levels, showing no increased risk compared to the general population, and no significant difference between pregestational and gestational hypothyroidism groups. Keywords: Pregestational, Gestational, Hypothyroidism, Thyroid hormone, Thyroid stimulating hormone, Thyroxine hormone