Patent ductus arteriosus (PDA) is the most prevalent cardiovascular defect and is more often seen in females; premature babies are at increased risk. For both sexes, a relationship exists between the risk of this defect occurring and the higher dimensions of the ductus arteriosus. In this study, we examined the relationship between the dimensions of the ductus arteriosus (diameter, length, capacity) and sex. We analyzed a total of 223 fetuses, 108 males and 115 females, ranging in age from four to eight months of intrauterinal life. All fetuses of normal karyotype were obtained from spontaneous abortions. None of the analyzed specimens demonstrated any visible malformations. The increase in the length and diameters of the ductus is linearly related to gestational age. The volumetric growth of this vessel was dependent on fetal age, according to the exponential function. The large number of analyzed specimens allows reliable determination of the ductus arteriosus dimensions in consecutive months of fetal life. The data obtained could be of prognostic value during echocardiographic follow-up in the fetus. We found that the dimensions analyzed did not differ with regard to sex. It is a contradiction that, more frequently PDA in females is caused with the gender differences in the dimensions of ductus arteriosus.