Predicting Neonatal Coarctation: In Search of a New ParadigmRajesh U. Shenoy, M.D., MS Wolfson Children’s Hospital 841 Prudential Drive, Jacksonville, FL 32207 Tel: (904) 202-8550 Fax: (904) 393-7808 E-mail: Rajesh.Shenoy@bmcjax.comCoarctation of the aorta (CoA) is a common congenital heart defect accounting for 5 – 8% of all forms of CHD1. It is a difficult diagnosis to make prenatally, since only 10% of the left ventricular output crosses the aortic isthmus, and flow into the descending aorta comes primarily from the patent ductus arteriosus. However, prenatal diagnosis of coarctation is of vital importance, since it would enable counseling of prospective parents, delivery at a tertiary institution, and institution of prostaglandin infusion if appropriate after the baby is born.CoA is usually suspected prenatally when there is discrepancy between the right and left heart structures. Multiple fetal echocardiographic parameters have been studied by various groups, in an effort to define those that can predict the likelihood of neonatal CoA. With advances in technology, novel parameters keep getting added to the mix. A systematic review2 of many of these studies concluded that z scores of diameters of mitral valve annulus, tricuspid valve annulus, aortic annulus, pulmonary valve annulus, and aortic isthmus, as well as ratios of right/left ventricles and pulmonary artery/ascending aorta were significantly different in fetuses that developed CoA in the neonatal period. The authors concluded that using a multiple-criterion prediction model may improve the detection of CoA in fetal life, and called for large multicenter studies to develop objective models to risk stratify these fetuses. A recent retrospective single-center study3 found discrepancies in z scores based on the multiple datasets available currently. The authors called for larger multi-center data in order to generate more reliable z scores. The same study identified the carotid-subclavian artery index and a product of isthmus/duct ratio and mitral valve/tricuspid valve ratio as highly sensitive and specific in identifying the fetus at risk for developing neonatal CoA. This was validated in a prospective group of fetuses.Fetal echocardiography likely overestimates the likelihood of neonatal coarctation, leading to parental anxiety and over-utilization of resources. However, only 20-35% of neonatal CoA is identified prenatally4. There exists a need for larger studies, preferably prospective and multi-center, to identify parameters which can more accurately identify the fetus at risk for neonatal CoA.In this issue of Echocardiography, Chen et al5 report on their prospective case-control matched study in which they assessed an exhaustive list of parameters which have been identified in other studies as predictive of neonatal CoA. On multi-variate analysis, they identified the diameter of the ductus arteriosus, aortic isthmus in the 3-vessel view, aortic arch between the 2nd and 3rd vessels, ascending aorta, and main pulmonary artery, in addition to the distance between the left common carotid and left subclavian arteries as significantly abnormal in fetuses who developed neonatal CoA. The AUC was robust for these parameters, and the authors also established a cut-off for dimensions at 28 weeks of gestation for these parameters (obviating the need for z-scores).This again is a single-center study in a defined ethnic group. Nearly half of the pregnancies where the fetus was identified as being at risk for developing neonatal CoA were not carried to term. We would do well to heed the call by the authors for a multi-center prospective study with diverse populations to examine the applicability of the findings from this comprehensive look at fetal parameters.1 Rosenthal E. Coarctation of the aorta from fetus to adult: curable condition or life long disease process? Heart . 2005;91 :1495–1502.2 Familiari A, Morlando M, Khalil A, Sven-Kirk S, Scala C, Rizzo G, Del Sordo G, Vassallo C, Flacco M, Manzoli L, Lanzone A, Scambia G, Acharya G, D’Antonio F. Risk Factors for Coarctation of the Aorta on Prenatal Ultrasound. Circulation 2017;135 :772-785.3 Fricke K, Liuba P, Weismann CG. Fetal Echocardiographic Dimension Indices: Important Predictors of Postnatal Coarctation. Pediatric Cardiology 2021;42 :517-25.4 Lytzen R, Vejlstrup N, Bjerre J, Petersen OB, Leenskjold S, Dodd JK, Jorgensen FS, Sondergaard L. Live-born major congenital heart disease in Denmark: incidence, detection rate, and termination of pregnancy rate from 1996 to 2013. JAMA Cardiol 2018;3 :829–837.5 Chen G, Mi J, Han Y, Qin K, Peng Y, Geng X, Zhou P, Yu T, Sun C, Gao B-L, Ge S. Changes of prenatal sonographic vascular parameters in Coarctation of the Aorta and the Risk Factors.Echocardiogr 2025;XX:XXX-XXX.