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Background: The process of physiological conversion of spiral arteries is dependent on the invasion of the interstitium and spiral arteries of the uterine wall by invasive extravillous trophoblast thereby creating a high flow-low resistance vessel. Quantitative data on restriction of trophoblast invasion and failure of spiral artery transformation are limited in preeclampsia., Aim: This study morphometrically analyzes interstitial trophoblast cells and trophoblast cells embedded in the wall of the converted spiral arteries within the decidua and myometrium of normotensive and preeclamptic Black African pregnant women., Methods: Placental bed biopsies were obtained from 25 normotensive pregnant women and 30 pregnant women complicated with hypertensive disorders. Biopsies were processed and immunostained for trophoblast cell identification, using anti-MNF 116 antibody. Image analysis of the trophoblast population within the decidua, myometrium and the spiral arteries was performed in the normotensive and in the severe proteinuric hypertensive groups., Results: The mean field area percentage of trophoblast cells observed in the decidua of the normotensive women was 22.79 +/- 2.1% in comparison to 18.14 +/- 1.53% in the severe hypertensive group (p < 0.01). In the myometrium, the mean field area percentage of interstitial trophoblast cells (both mononuclear and multinuclear) was 10.04 +/- 2.1% of the field area of the normotensive group compared to 2.81 +/- 0.67% in the severe hypertensive group (p < 0.001). The mean field area percentage occupied by trophoblast cells in myometrial spiral arteries was 10.15% in the normotensive group compared to none in the severe hypertensive group. The latter group displayed medial disorganization, hyperplasia and endothelial vacuolation., Conclusion: This study demonstrates restricted invasion of the trophoblastic cells in preeclampsia. This inadequate invasion may influence vascular remodeling required for delivering adequate volumes of maternal blood to the placenta.