The main pathology leading to mortinatality has been determined. It is shown that in 57.8% of cases mortinatality is associated with placental insufficiency, the reason for which can be found out by the pathoanatomical study of the afterbirth. It is proposed to differentiate afterbirth disorders of implantation, placentation, circulation and inflammatory changes. Fifty per cent of neonates are shown to die from the respiratory failure associated with the formation of atelectasis, hyaline membranes and edema with pulmonary hemorrhages. Next in frequency are cephalic ventricle extravasations. The main pathogenetic factor of both neonatal pathologies is prematurity with functional and morphological tissue immaturity.