Background: Erythropoietin (EPO), an essential stimulator of erythropoiesis produced by the fetal liver, is important both in vascular remodeling and modulation of the endothelial response in the pulmonary vasculature. In addition, EPO guides alveolar development, along with retinoic acid (RA). EPO is a direct target of RA, and the retinoid pathway is altered in the nitrofen-induced congenital diaphragmatic hernia (CDH) model. In the present study, we tested the hypothesis that the synthesis of EPO is suppressed in a rat model of CDH. Materials and Methods: Pregnant rats were treated with either nitrofen or vehicle on gestational day 9 (D9). Fetuses were sacrificed on D19 and D21 and divided into control and CDH groups. Immunohistochemistry and quantitative real-time polymerase chain reaction (RT-PCR) were performedto determine the expression ofEPOin the fetal liver and kidney. We also estimated the expression of EPO receptor in the fetal lung. Results: The relative EPO mRNA expression in the liver on D19 and in the kidney on D21 were significantly lower in the CDH group than in the controls (P = 0.0008 and P = 0.0064, respectively). In addition, the results of immunohistochemistry supported the findings from the RT-PCR analysis. No significant changes were noted in the expression pattern or EPO receptor levels in the fetal lungs of the CDH group compared to the controls. Conclusions: Our results reveal the suppressed EPO synthesis in the CDH fetus, which may contribute to the pathogenesis of lung hypoplasia and modification of pulmonary vasculature in the CDH rat model. (C) 2016 Wiley Periodicals, Inc.