Effects of ‘rescue’ dose of antenatal corticosteroids on placental histopathology in preterm births

Introduction: Antenatal corticosteroids (ACS) are frequently used to reduce neonatal morbidity in preterm births (PTBs). A ‘rescue’ dose of ACS can be administer, if the risk of PTB remains. Some reports indicated that repeated doses of ACS might impact placental histology and possibly its function. We aimed to study whether repeated doses of ACS effect placental histopathology and pregnancy outcome. Methods: The medical files and placental reports of all PTB, at 24-33⁶/₇ weeks, between Nov 2008–Dec 2019, were reviewed. The study population was divided into three groups; no-ACS (PTBs without ACS treatment), one-ACS (PTBs after a full or partial ACS course), and rescue-ACS (PTBs after a ‘rescue’ course of ACS). Placental lesions were classified according to “Amsterdam” criteria into maternal and fetal vascular malperfusion lesions, maternal and fetal inflammatory responses and chronic villitis. Placental lesions and pregnancy outcome were compared between the study groups. Results: The no-ACS group (n = 58) was characterized by increased rates of PTB<28 weeks (p = 0.003), perinatal death (p < 0.001) and composite neonatal infectious morbidity (p = 0.022), as compared to the one-ACS group (n = 331) and the rescue-ACS group (n = 53). Placental MIR lesions were more common among the rescue-ACS group, compared to the one- and no-ACS groups (p = 0.022). Other placental lesions did not differ between the groups. On multivariate logistic regression analysis, MIR lesions were independently associated with rescue-ACS treatment (aOR 3.00, 95% CI 1.10–8/17, p = 0.031). Discussion: Rescue course of ACS is associated with increased rate of placental maternal inflammatory response. These findings probably result from maternal stress stimuli without an adverse impact on early neonatal outcome.