Impact of antenatal corticosteroid exposure on thymus size in premature infants.

BACKGROUND This study examined the effect of corticosteroids on the thymic index (TI) and the thymus/weight index (TWI) in infants exposed to antenatal corticosteroids (ACS). METHODS This prospective study was conducted between August 2014 and October 2018. A thymus ultrasound was performed to assess thymus size on the second day of life. Thymus size was assessed as TI and TWI. RESULTS In total, 167 neonates (≤34 weeks gestation)  constituted the study population, including 94 ACS-exposed infants and 73 untreated infants. The treatment group exhibited significantly lower birth weight and significantly shorter birth length than the ACS (-) group. Therefore, TI was smaller in the treatment group than in the untreated group (6.96 ± 4.05 cm3 vs. 5.64 ± 3.39 cm3). The TWI was 3.69 ± 1.8 cm3/kg in the ACS (-) group versus 3.32 ± 1.56 cm3/kg in the ACS (+) group. The median anteroposterior diameter of the right lobe was 1.33 cm (range, 0.45-2.40) in the ACS (-) group compared to 1.15 cm (range, 0.47-2.40) in the ACS (+) group. The median anteroposterior diameter of the left lobe was 1.40 cm (range, 0.43-2.20) in the ACS (-) group and 1.19 cm (range, 0.32-2.36) in the ACS (+) group. The median largest sagittal area was 2.64 cm2 (range, 0.5-5.46) in the ACS (-) group versus 2.20 cm2 (range, 0.55-5.90) in the ACS (+) group. CONCLUSION We found that TWI was not significantly changed by ACS exposure in premature infants.