Congenital Hypothyroidism in Preterm Newborns: A Retrospective Study Arising from a Screening Program in Fars Province, Southwestern Iran

OBJECTIVES: There is a high interest in the early diagnosis of hypothyroidism in preterm newborns for preventing any intellectual disability. Our study sought to determine the incidence of abnormal thyroid-stimulating hormone (TSH) between three and six days old and in weeks two, six, 10, and 12 after birth to evaluate the validity of repeating the test in premature infants. METHODS: We conducted a retrospective review of 320 886 live births in Fars province, Southwestern Iran, from March 2014 to October 2017. TSH levels in premature infants were measured by heel prick test, and the data was collected from the central newborn screening center of Fars province. RESULTS: The number of premature newborns was 15 381, and the prevalence of hypothyroidism was 2.3%. Among 355 premature newborns with high TSH, 31.3% was detected in three to six days of life, 43.9% in the second week, 14.4% in the sixth week, 9.9% in the tenth week, and 0.6% in the twelfth week as hypothyroidism. CONCLUSIONS: Our results showed that thyroid screening of preterm infants needs retesting in two, six, and 10 weeks after to detect cases in newborns who would not otherwise be identified.