[Histologic placenta findings in diastolic zero or negative flow of the umbilical arteries: a prospective study with reference to the duration of clinical observation].

37 cases with enddiastolic zero flow or reverse flow (dZRF) in the umbilical arteries were compared with 37 gestational age-matched controls. In dZRF the placenta is significantly smaller (weight and basal area) throughout the entire gestational age. Vascularisation of the villous tree is often reduced in cases with dZRF, but the findings are not uniform. However, there is a direct interdependence of the histologic findings of villous maturation, terminal villus deficiency, reduced vascularisation and endangiopathia obliterans from the duration of clinical observation. The longer the control period was, the higher was the amount of accelerated villous maturation, angiosis of terminal villous vessels, less endangiopathia obliterans, with simultaneously improved foetal outcome. We conclude from these data, that the main placental lesion, which may cause dZRF, is located in the central villous tree and vascular tree, which is possibly related to the smallness of the placenta, whereas the changes in the terminal villi may exercise compensatory functions and may influence foetal outcome.