Introduction: Congenital Hypothyroidism (CHT) is a condition in which the thyroid stimulating hormone (TSH) is equal to or more than 10 MU/L and the thyroxine hormone (T4) is less than 6.5 M/L. CHT is one of the most important preventable causes of mental retardation in infants. The present study aimed to determine the incidence of CHT and the associated factors.

Method: At first, a descriptive research was done to examine the incidence of CHT in the period of 2006-2014 in Shadegan city, Khuzestan province. Then, a case-reference and a case-control study was done to investigate the relationship between CHT and demographic characteristics, environmental factors and medical factors. The cases in this study were neonates with CHT (transient and permanent). The results showed that the venous TSH score for these neonates was equal to or higher than 10 MU/L and their T4 level was lower than 6.5 MU/L. The subjects in the control group were infants that did not suffer from CHT whose venous TSH and T4 scores were lower than 10 MU/L and higher than 6.5 MU/L, respectively. The relationship between the aforementioned factors with the illness was determined using multiple logistic regression statistical model. The SPSS 18 software was used to analyze the findings of this research.

Findings: In this study, the incidences of neonatal CHT in Shadegan were 17, 21.5 and 12.59 per thousand newborn infants in 2012, 2013 and 2014, respectively.

Conclusion: The parents' record of consanguineous marriage increases the likelihood of developing CHT; therefore, couples that wish to marry have to be educated and made aware in marriage counseling centers, both in the field of consanguineous marriage and CHT.

Keywords: incidence, screening, transient, permanent, congenital hypothyroidism