Fetuses with pulmonary atresia or pulmonary stenosis with intact ventricular septum manifest variable degrees of right ventricle hypoplasia and inadequacy. We studied the relationship between prenatal echocardiographic parameters and their progression through gestation as potential predictors of postnatal single-ventricle or two-ventricle care strategy. Serial fetal echocardiograms of pulmonary atresia (n = 28) or severe pulmonary stenosis (n = 8) and intact ventricular septum were reviewed. Measurements included tricuspid valve and mitral valve diameter and Z scores, degree of tricuspid regurgitation, presence of subaortic stenosis, presence of coronary artery fistulae, and Doppler pulsatility indices in middle cerebral and umbilical artery. Data were compared between first and last fetal studies. Subjects were divided based on postnatal course of single- or two-ventricle repair. Tricuspid valve size of those destined for single ventricle is smaller than of those destined for a two-ventricle repair at first study (26w, Z score −4.22 v −1.83, p < 0.001) and at final study (35w, −4.94 v −1.42, p < 0.001). Tricuspid valve and right ventricle grow in those destined for two ventricle, but not single-ventricle palliation. Tricuspid valve Z score = −3 at first or last study discriminated between single- or two-ventricle repair, except in two unusual cases with significant subaortic stenosis. Tricuspid valve Doppler-derived parameters of middle cerebral artery and umbilical artery did not distinguish between groups. In the fetus with pulmonary atresia or stenosis and intact ventricular septum, tricuspid valve Z score ≥−3, presence of important tricuspid regurgitation, absence of coronary fistulae, and absence of subaortic stenosis are associated with a two-ventricle postnatal strategy.