Uteroplacental arterial changes related to interstitial trophoblast migration in early human pregnancy

Abstract

Morphometric and statistical techniques were used to assess the relation of [human] myometrial interstitial trophoblast to the uteroplacental vasculature in 27 intact hysterectomy specimens ranging from 8-18 wk gestation. The volume density of cytotrophoblast in the myometrium and in particular the proximity of such trophoblast to the placental bed spiral arteries correlated significantly with morphological alterations in these vessels. The changes included swelling of endothelium, hypertrophy of individual medial smooth muscle cells and edema and disruption of the architecture of the vessel wall as a time-related continuum. Some of the changes, such as swollen endothelium and basophilia of medial smooth muscle cells were noted also in spiral arteries in the non-placental bed endometrium but to a considerably less extent than in the placental bed. Intimal vacuolation was common to placental bed and nonplacental bed arteries, increased with gestational age and can be considered as a non-specific feature. The migration of endovascular trophoblast into the myometrial spiral arteries in the 2nd trimester occurred only when these arteries had been considerably altered in their morphology. Evidently, migratory interstitial cytotrophoblast probably has a role to play in the preparation of the myometrial segments of the uteroplacental arteries for the 2nd wave of endovascular trophoblast migration that occurs in the 2nd trimester of human pregnancy.