Ventricular discrepancy as a sonographic sign of coarctation of the fetal aorta: how reliable is it?

The purpose of this study was to assess the predictive value and sensitivity of discrepant ventricular size for fetal aortic coarctation. Postnatal follow-up data were obtained in 42 fetuses in whom ventricular size discrepancy (left ventricle smaller than right ventricle) was recognized on an obstetrical sonogram. Additionally, from postnatal records, we identified infants with coarctation who had had an obstetrical sonogram after 16 weeks. Fourteen of the 42 fetuses had coarctation or other aortic arch obstruction after birth (33% positive predictive value). Eight (62%) of 13 fetuses with ventricular discrepancy recognized before 34 weeks had coarctation, compared with six (21%) true positive cases among 29 recognized after 34 weeks (P = 0.01, Fisher's exact test). Of 21 infants with coarctation, ventricular discrepancy had been recognized by prenatal sonography in 13 (62% sensitivity). Ventricular discrepancy has moderate sensitivity and mediocre positive predictive value for coarctation. The limitations of this finding for diagnosing coarctation, particularly a higher false positive rate after 34 weeks, must be recognized, but it is still a useful sign to identify this potentially ductus-dependent lesion.