Cross-sectional analysis of maternal and neonatal factors influencing cord blood TSH and free T4 levels in congenital hypothyroidism screening

Abstract

Abstract Background Congenital hypothyroidism (CH) is the leading cause of cognitive impairment in children. Although screening programs have been successful in identifying cases of congenital hypothyroidism (CH), the high rates of recalling individuals for further testing and the occurrence of false positive results place a significant strain on healthcare systems globally. While cord blood thyroid-stimulating hormone (CBTSH) is commonly used as a screening test for congenital hypothyroidism (CH), there is less data available on its effectiveness in Iran. The objective of this study was to assess the levels of TSH and Free T4 in umbilical cord blood and examine their correlation with maternal and neonatal variables, as well as heel-stick TSH. Methods In this cross-sectional study, 120 mothers and their newborns were recruited from Semnan’s Amir-Al-Momenin Hospital in 2021. The maternal characteristics examined encompassed age, BMI, gravidity (number of pregnancies), history of abortions, preeclampsia, gestational diabetes, gestational age, and delivery technique. The neonatal parameters encompassed in the study were sex, birth weight, number of gestation births, Apgar ratings, and arterial blood cord gases. The average values of Free T4 and CBTSH were measured and compared with these parameters. TSH levels were measured by a heel-stick procedure on days 2–3 following birth. The statistical analysis comprised of the Mann–Whitney U test, Kruskal–Wallis test, and Spearman correlation test. The diagnostic accuracy of CBTSH was evaluated using ROC curve analysis. Results The average concentration of CBTSH was substantially greater in preterm neonates and males compared to term newborns and females (P = 0.039 and P < 0.001, respectively). Newborns delivered by cesarean section exhibited significantly lower levels of CBTSH compared to those delivered vaginally (P = 0.040). A significant positive connection was seen between CBTSH and heel-stick TSH (P < 0.001). The average level of Free T4 in umbilical cord blood was substantially greater in neonates from women who had been pregnant multiple times compared to those who had been pregnant for the first time (P = 0.023). There was no statistically significant correlation observed between umbilical cord blood Free T4 and TSH levels and factors such as maternal age, preeclampsia, gestational diabetes, twin or singleton delivery, Apgar scores, birthweight, and cord gases (P > 0.05). The most effective threshold value for CBTSH in detecting potentially abnormal cases of hypothyroidism was determined to be 14.75 mIU/L. Conclusions Delivery method, gestational age, and male gender were significant factors affecting umbilical cord TSH levels. These factors should be considered when interpreting CBTSH data. This study provides evidence for the inclusion of CBTSH as a predictive factor in CH screening programs.