Is analysis of physiological late gestation ventricular-arterial disproportion futile?

Background Ventricular-arterial disproportion is a frequent observation in the third trimester and mostly considered physiological. It is also an indirect prenatal sign for postnatal coarctation. We sought to investigate the remnant risk for coarctation and its possible risk factors in a fetal population with physiological late gestation asymmetry. Methods This was a monocentric, retrospective study conducted from 2014 till 2017 in a Fetal Cardiology Unit. All fetuses referred for third trimester asymmetry with pulmonary artery/aorta ratio > 1.2 were included. Annular sizes, arterial Z-scores, valve ratios, isthmus size if available and minor associated cardiac defects were analyzed. Results 151 fetuses were referred at a mean gestational age of 33.5 SA. After fetal echocardiography, 2% (3/151) were considered at high risk for coarctation because of a hypoplastic arch and/or a small left outflow tract or isthmus. They were scheduled to deliver in a tertiary referral center. Two of these 3 newborns developed coarctation. In 98% of fetuses asymmetry was considered physiological with a normally sized aortic arch without the “shelf sign”. All infants had an early ambulatory echocardiography that revealed coarctation in 7/148 cases (4.7%). There were no significant differences in mean arterial annular sizes, aortic and pulmonary Z-scores, pulmonary artery/aorta ratio, atrioventricular annular sizes, tricuspid/mitral valve ratio, presence of ventricular septal defect or left persisting superior caval vein between the two groups. Conclusion Remnant risk for coarctation in a fetal population with physiological late gestation asymmetry is