Abstract

Background and Objectives: Congenital hypothyroidism is one of the important factors of mental retardation and neonatal prevention. The aim of this study was to evaluate the risk factors associated with congenital hypothyroidism and introducing a preventive model. Materials and Methods: By a case-control study all newborns suffering from congenital hypothyroidism who were identified through a screening program during 1389-1395, were selected as the case group and for each case, a healthy neonate born at the same date and the same area was selected as the control. The required information was collected by a questionnaire and entered into SPSS version 20. Data were analyzed using T test, Chi-square, Fisher exact test and logistic regression and then the results of the logistic regression model were compared with discriminant function model. The p value equal or less than 0.05 was considered as significance level in all tests. Findings: Totally 104 neonates with congenital hypothyroidism and the same number among healthy infants were enrolled in the study during 1389 – 1395. Among control group, 52% were female (54 neonates) and 48% were male (50 neonates) and among case group, 43.3% (45 neonates) were female and 56.7% (59 neonates) were male. The mean ± SD of weight for the case group was 2995. 385 ± 613.1 grams and for the control group was 3176. 731 ± 490.2 grams with a significant difference (p = 0.019). This study showed that the chance of having a congenital hypothyroidism at a  gestational age ≤37 weeks was 8.8 times more than gestational age >37 weeks (OR = 6.8; 95%CI:71.3-89%,  P = 0.049). Also, the chance of having congenital hypothyroidism among newborns with a positive history of hypothyroidism in the family was 3.03 times more than those with a negative history (OR = 3.03; 95%CI: 0.13-9.8%, P = 0.043). There was no a significant relationship between other environmental, familial and medical factors with the risk of congenital hypothyroidism. Also, the diagnostic function model showed that using the variables of fetal age below 37 weeks, the birth weight of infants and the existence of a positive familial history of thyroid disease can predict the congenital hypothyroidism in the baby with a specificity and sensitivity of 85.6% and 33.7% respectively. Conclusion: The study showed that the history of thyroid disease in the family, the gestational age and the weight of baby at birth are factors associated with congenital hypothyroidism. Considering the related factors, a preventive model was presented for congenital hypothyroidism.