Objectives: To establish the prevalence of coronary arterial abnormalities in mid-trimester fetuses with pulmonary atresia with intact ventricular septum, and whether their presence correlates with right ventricular morphology. Background: The presence of coronary arterial fistulas significantly alters the surgical options and prognosis for patients with pulmonary atresia with intact ventricular septum. The lesion can reliably be diagnosed using fetal echocardiography, and further definition of the prognosis is important for counselling parents. Methods: We examined the hearts of 39 pathological specimens diagnosed during fetal life, 3 of whom died postnatally. Coronary arterial abnormalities were defined as non-connection of the left or right coronary arteries to the aorta, ostial stenosis, marked tortuosity, dilation, thickening or abnormal myocardial branching. Mild tortuosity, or myocardial bridging, were considered normal. We measured the dimensions of the tricuspid valve along with the inlet and outlet portions of the ventricles. Ebstein's malformation, tricuspid valvar dysplasia, and the presence or absence of the infundibulum, were especially noted. We examined also 12 normal hearts as controls. Results: Coronary arterial abnormalities were found in 14/39 (36%). The dimensions of the right ventricle and tricuspid valves, and the gestational ages of the fetuses, were compared for these 14 with the 25 having no abnormalities using independent t-tests. The gestational ages were similar, 21.9 vs 21.1 weeks. The mean dimensions of the tricuspid valve, median z-scores, and right ventricle were smaller, 2.9 vs 7.2 mm; p < 0.002; −4.46 vs 0.23; p < 0.03; and 6.9 vs 13.7 mm; p < 0.002, for those with coronary arterial abnormalities. Ebstein's malformation, or dysplasia of the tricuspid valve, was present in 4 of 14 with, vs 15 of 25 without, coronary arterial abnormalities. A patent infundibulum was noted in 34 of 39 specimens. Conclusions: Mid-trimester fetuses with pulmonary atresia with intact ventricular septum already exhibit coronary arterial abnormalities, with a prevalence of 36%. The presence of a patent infundibulum confirms that atresia of the pulmonary valve is an acquired process. Coronary arterial abnormalities are seen in 50% of those with hypoplastic right ventricles, but less frequently in the presence of well developed ventricles. This is important information for those involved in counselling parents.