Bias in the prenatal lung measurements in fetal congenital diaphragmatic hernia with intrauterine growth restriction

Objectives: The failure of a fetus to develop to its full potential due to maternal or placental factors is known as intrauterine growth restriction (IUGR). Fetal head growth is usually preserved in that situation producing a potential discordance between head and body size. Our goal is to discover if IUGR has an impact on the prenatal ultrasound measurements taken to assess pulmonary development in congenital diaphragmatic hernia (CDH). Methods: A retrospective chart review (IRB#2017-6361) was performed on all prenatally diagnosed CDH patients from 2007 to 2016. Patient demographics, fetal and neonatal anthropometric measurements, and fetal lung parameters were the main subjects of the data that were gathered. Fetal growth was assessed by the curves based on US data by Olsen et al. and by Peleg et al. Of 147 CDH patients, 19 (12.9 %) patients were diagnosed with IUGR before the 30th gestational week while there were 20 (13.6 %) patients after the 30th gestational week. Results: Patients with IUGR and the observed-to-expected lung-to-head ratio (O/E LHR) less than 25 % had better survival rates both to discharge and date compared to non IUGR group (p=0.226, OR 2.25 95 % CI 0.60-1.08 and p=0.175, OR 2.40 95 % CI 0.66-1.17, respectively). Moreover, the ECMO need of the patients who had IUGR and O/E LHR less than 25 % was significantly less than the patients without IUGR (38.5 vs. 80.0 %, p=0.005). Conclusions: This study confirms that the intrauterine measurements to predict pulmonary hypoplasia in CDH patients are misleading in the presence of IUGR and cause an overestimation.