[Morphological characteristics of a second wave of cytotrophoblast invasion].

In the morphological studies of cytotrophoblast invasion into the uteroplacental area, the final activity of interstitial and intravascular cytotrophoblasts is usually limited to 18-20 weeks of pregnancy. The activity of cytotrophoblast invasion from 15 weeks to the end of pregnancy is morphologically and semiquantitatively assessed on the basis of a collection of scrapes from the uterine cavity and uteri amputated for myomas, early bleedings and iatrogenias (the conditional standard of pregnancy). The second wave of cytotrophoblast migration is first shown to peak at 17-24 weeks in the central zone of the uteroplacental area due to the simultaneously high activity of interstitial and intravascular cytotrophoblasts attacking the myometrial radial arteries. Then both components of cytotrophoblast invasion move to the marginal sites of the uteroplacental area where they are highly active up to 33-36 weeks. The gestational rearrangement of adjacent myometrial radial arteries in the center and around the periphery of the uteroplacental area results in a continuous rise in the volume of the uterine arterial blood entering the intervillous lacuna and hemochoreal exchange leads to adequate fetal nutrition and development. Impairments in the course of the second wave of a cytotrophoblast wave are of importance in interpreting the pathogenesis of severe obstetric complications, such as preeclampsia, eclampsia, intrauterine growth retardation, miscarriage, and many others.