OBJECTIVE The aim: To assess morphometric parameters of placentas and to evaluate the correlation between the placental disk shape, the site of the umbilical cord insertion and the birth weight of dichorionic twins. METHODS Materials and methods: The geometry of placentas, distances between umbilical cord insertion sites and the centroids of the disks were measured in 135 pairs of dichorionic diamniotic twins. The impact of the above-mentioned parameters on the birth weight and placental mass was analyzed. RESULTS Results: In terms of weight and geometric parameters of placentas, no proven discrepancy between different types of twins and inside pairs was found. A strong correlation was established between the placental weight and birth weight (r = 0.71, p < 0.05). Both the placental weight and birth weight showed the strong correlation with S*Circ (r = 0.62, p < 0.05). The displacement of the umbilical cord insertion site from the centroid of the placenta was negatively correlated with its mass (r = -0.428, p < 0.0001) and birth weight (r = -0.6115, p < 0.0001). The displacement along the maximum axis proved to play a significant role. CONCLUSIONS Conclusions: In dichorionic diamniotic twins, the area of the placentas plays the determining role in the functional activity of the organ, which increases when its shape approaches the circle. The area of the placenta multiplied by its circularity had the strongest correlation with birth weight and placental mass. The farther from the centre the umbilical cord is inserted, the lower the functional capacity of the placenta is.