LAUSR

ObjectiveTo examine the effect of antenatal corticosteroid administration (ACS) on fetal thymus growth in women who received ACS compared with gestational-age-matched controls.Study designFetal thymus size and growth were measured in women at risk for preterm delivery who received ACS and compared with a matched cohort of women who were at low risk for preterm delivery and did not receive ACS. Fetal thymus perimeter and diameter were measured by 2-D ultrasound at baseline and every 2 weeks until delivery.ResultsAfter adjusting for confounders, ACS exposure was associated with a significant reduction in thymus perimeter size (−0.70; 95% CI: −1.33, −0.07; P = 0.03). For every additional week of exposure, thymus growth trajectory was significantly decreased in ACS-exposed fetuses (P = 0.04).ConclusionThe association between ACS and reduced fetal thymus growth should be further examined to establish the impact of ACS on childhood thymus development and immune programming.