Objectives: We aimed to investigate the 13 fetal cases with hepatic veins opening variously into the inferior vena cava within the diaphragm.Methods: The study was carried out on 13 human fetuses (seven males and six females) aged between 21-40 weeks of gestation. The diaphragm, foramina on the diaphragm, inferior vena cava and the hepatic veins were exposed by thoracoabdominal dissections. In 13 fetal materials, variations in the foramina of the hepatic veins into the inferior vena cava on the undersurface of the diaphragm were observed.Results: In 13 fetal materials, the hepatic veins did not directly open into the inferior vena cava but formed accessory foramen/foramina on the undersurface of the diaphragm and joined the inferior vena cava within the diaphragm. Accompanying the caval opening, there were 1-3 accessory foramina on the inferior but not superior surface of the diaphragm in 13 cases. A single hepatic vein in nine cases, two hepatic veins in two cases and three hepatic veins in two cases were found to open into the inferior vena cava within the diaphragm.Conclusion: Physicians and researchers should be aware of the fact that during the fetal period, hepatic veins can open into the inferior vena cava with different ways within the diaphragm. These variations need to be taken into consideration in evaluating the caval opening on the diaphragm during obstetric ultrasonography and surgical interventions in the prenatal period.