Objective: Cardiac ventricular size disproportion is a marker for aortic coarctation (CoA) in fetal life, but approximately 50% of fetuses do not have CoA after birth. The aim of this study was to evaluate the postnatal outcome of cases with fetal ventricular size disproportion in the absence of CoA after birth. Methods: All cases with fetal isolated ventricular size disproportion diagnosed between 2002 and 2015 were extracted from a prenatal congenital heart defects regional registry. Cases were stratified according to presence or absence (non-CoA) of aortic arch anomalies after birth. Postnatal outcome of non-CoA cases was evaluated by assessing the presence of cardiac and other congenital malformations, genetic syndromes and other morbidity after birth. Non-CoA cases were further classified according to whether they had cardiovascular pathology requiring medication or intervention. Results: Seventy-seven cases with fetal ventricular size disproportion were identified, of which 46 (60%) did not have CoA after birth. Of these, 35 did not require cardiovascular intervention or medication, whereas 11 did. Of the 46 non-CoA cases, six presented with clinical pulmonary hypertension requiring treatment after birth, cardiac defects were present in 24 cases and syndromic features were seen in four. Overall, 43% of all non-CoA children were still under surveillance at the end of the study period. Conclusions: The postnatal course of cases with fetal ventricular size disproportion is complicated by prenatally undetected congenital defects (46%) and pulmonary or transition problems (35%) in a significant number of cases that do not develop CoA. Proper monitoring of these cases is therefore warranted and it is advisable to incorporate the risks for additional morbidity and neonatal complications in prenatal counseling. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.