The Relationship Between Maternal Hypothyroidism and the Incidence of Congenital Hypothyroidism in Infants: A Cross-Sectional Study

Background: Congenital hypothyroidism (CH) can influence neonates' neurodevelopment. There are controversies on the cause of infantile hypothyroidism and its relationship with maternal hypothyroidism. Objectives: This study aimed to investigate the relationship between maternal hypothyroidism and the incidence of CH. Methods: This cross-sectional study was conducted on 712 newborns with hypothyroidism born in Fars province, Iran, between 2018 and 2020, identified through the national screening program for genetic, metabolic, and endocrine congenital diseases recruited by the census sampling method. The information on infants' files was recorded in a researcher-made checklist. Descriptive data were reported by mean +/- SD and No. (%). The independent t-test, chi-square test, Pearson correlation, and Spearman's rank correlation coefficient were used to evaluate relationships between variables. Results: Of 179,448 infants screened, 712 (4 of 1,000 live births) had CH with a mean thyroid stimulating hormone (TSH) level of 22.34+24.8 mlU/L. Of these, 252 infants (35.4%) had a family history of hypothyroidism in the mother (OR = 4.951, P < 0.001). There was a significant relationship between CH and maternal hypothyroidism. Moreover, there was a significant difference in the mean TSH level between hypothyroid infants born to mothers with a history of hypothyroidism (19.10 +/- 21.30 mlU/L) and those who had healthy mothers (24.23 +/- 26.44 mlU/L, P = 0.027). The prevalence of CH in 2018, 2019, and 2020 were reported to be 0.34%, 0.4%, and 0.45%, respectively. Conclusions: Our results showed a significant relationship between maternal hypothyroidism and CH. Considering the importance of the prompt diagnosis of CH, especially in high-risk groups such as infants of hypothyroid mothers, it is recommended to conduct more studies to design more precise guidelines to screen infants who are at risk of CH.