Based on 200 fetal blood vessel corrosion casts of human placentas, an attempt was made to establish the prevalence of certain developmental placenta malformations. The placentas came exclusively from uncomplicated pregnancies of a normal course, which resulted in births of healthy newborns without visible developmental malformations. Single umbilical arteries occurred in 1.5% of cases, velamentous placentas - in 2% of cases,accessory placentas - in 5.5% of cases, absence of Hyrtl's anastomoses - in 2.5% of cases, and false umbilical artery knots in 66% of cases.

Keywords: human placentas, developmental malformations, corrosion casts