Existing morphologic classifications of placenta immaturity are analyzed on the basis of stages of the placenta villi normal histogenesis. 6 variants of its pathologic immaturity are distinguished: mesenchymal, embryonal, intermediate and differentiated villi, variant of chaotic sclerotized villi, variant of precocious villi maturation. These variants result in the foetal hypotrophy or its death at all stages of its antenatal development. 2 variants comprise a relative placenta immaturity: variant of a dissociated development of kotiledons and that of deficiency of terminal specialized villi. They occur in both risk groups of newborns and in normal pregnancy. Revealing of the above variants allows one to determine the time of the antenatal damage of developing placenta.