PROBLEM: Angiogenesis and vasculogenesis appear to be of critical importance for the success of pregnancy. Recent data have emphasized that pregnancy complications, such as abortion or pre-eclampsia, are linked with vascular pathologies. The aim of this study was to quantify human first-trimester decidua microvascular density, using two novel, highly specific endothelial cell markers, VE-cadherin and endoglin. METHOD OF STUDY: We collected decidua from women undergoing termination of normal pregnancies. VE-cadherin and endoglin were localized by immunohistochemistry. The blood vessel densities detected by VE-cadherin or endoglin-stainings were microscopically quantified per mm(2). RESULTS: Endothelial cells in first-trimester human decidua both express VE-cadherin and endoglin. The microvascular density detected by VE-cadherin-staining varied from 32.2 +/- 1.7 in decidua basalis, to 30 +/- 0.6 in decidua parietalis. For the endoglin-staining, the values varied from 37.5 +/- 3 in decidua basalis, and 26.7 +/- 1.2 in decidua parietalis. CONCLUSIONS: Our data shows that both VE-cadherin and endoglin are good candidates to highlight the decidual endothelial cells, and to quantify the blood vessels density of endometrium.