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[Perinatal risk factors for congenital hypothyroidism in very preterm infants: a multicenter prospective study].

Objective: To investigate the incidence and perinatal risk factors of congenital hypothyroidism (CH) in very preterm infants. Methods: This prospective, multicenter observational cohort study was conducted at 33 neonatal intensive care units based on the data from Sina-northern Neonatal Network (SNN). Perinatal information and thyroid function of 3 179 very preterm infants with gestational age <32 weeks who were born from January 2019 to June 2021 was collected. According to the occurrence of CH during hospitalization, all the infants were assigned into CH group and non-CH group. Chi square test, Fisher exact probability method, rank sum test and multivariate Logistic regression model were tested to detect the perinatal risk factors for CH. Results: A total of 3 179 very preterm infants were enrolled with 56.4% (1 793/3 179) male. The incidence of CH was 6.9% (220/3 179), in which the incidence for extremely low birth weight infant (ELBWI) and extremely preterm infants (EPI) of gestational age <28 weeks were 13.5% (64/475) and 13.9% (66/475), respectively. On Logistic regression analysis, maternal hypertensive disorders of pregnancy (OR=1.59, 95%CI 1.14-2.23, P=0.007) and multiple birth (OR=1.60, 95%CI 1.18-2.17, P=0.003) were both significant perinatal risk factors of CH. In addition, gestational age (OR=0.81, 95%CI 0.71-0.93, P=0.002), birth weight (OR=0.99, 95%CI: 0.98-0.99, P<0.001) and 1 min Apgar score (OR=0.92, 95%CI 0.86-0.98, P=0.008) were protective factors. Conclusions: The incidence of CH is high in very preterm infants which increased with the decreased birth weight and gestational age. For very premature infants with perinatal high risk factors such as hypertensive disorders of pregnancy, attention should be paid to assess thyroid function status dynamically.