Abnormal Fetal/Neonatal Lung Development Manifested as Some Functional Heart Abnormalities During the Third Trimester of Fetal Life

<b>Background</b>: Pulmonary hypertension (PH) in newborns is a rare but serious condition and potentially life-threatening disorder, often initially confused with congenital heart disease due to overlapping echocardiographic findings in the late third trimester. Evidence on prenatal predictors of postnatal PH is limited. We aimed to describe detailed third-trimester echocardiographic findings associated with postnatal PH in infants with prenatally suspected CoA based on a retrospective case series. <b>Methods</b>: We reviewed 18 years of fetal echocardiography (2004-2022) in a tertiary maternal-fetal-neonatal center. We identified fetuses with suspected coarctation of the aorta (CoA) in late gestation who were delivered at term (≥37 weeks) and had prolonged neonatal hospitalization (>10 days) without cardiac surgery or catheterization. Z-scores for cardiac dimensions were calculated. All examinations were performed by experienced fetal cardiologists. Postnatal evaluations confirmed PH based on echocardiographic and clinical findings. <b>Results</b>: Among 19,836 fetuses examined, 138 were prenatally suspected of CoA. In 70 cases, this diagnosis was not confirmed postnatally (false positives). Of these, eight infants (0.04% of the total cohort) developed postnatal PH. Postnatally, all eight neonates required intensive care. Prenatal features included ventricular/atrial disproportion (7/8), cardiomegaly (8/8), main pulmonary artery dilatation (10.2 ± 2.2 mm; Z-score +2.7 ± 1.3), tricuspid regurgitation (8/8), pulmonary regurgitation (4/8), and interventricular septal hypertrophy (>4.5 mm in 5/8). Postnatal evaluations confirmed PH based on echocardiographic criteria (elevated right ventricular pressure, septal flattening/bowing, right ventricular dilation or dysfunction, and abnormal shunt direction) combined with clinical compromise. All infants received prostaglandin E1 (PGE1) initially; none required extracorporeal membrane oxygenation-ECMO. Three died, while five survived with medical management (oxygen, inhaled nitric oxide, sildenafil). <b>Conclusions</b>: Specific functional abnormalities on late third-trimester echocardiography may indicate impaired pulmonary vascular adaptation and predict postnatal PH, particularly in cases initially suspected of CoA. Recognition and awareness of these findings can guide delivery planning, neonatal surveillance, and timely intervention. Prospective multicenter studies are needed to validate these associations and refine prenatal screening protocols.