Abstract: Objective: To test estradiol(E2) levels in the maternal peripheral blood, villi and placenta in the first trimester and term parturition, as well as the estradiol level of umbilical artery blood in term delivery. Culture trophoblast cell line BeWo in vitro to investigate the role of E2. Methods：This study included 20 unwilling pregnant women who want to have early artificial abortion and 20 pregnant women of full term cesarean delivery. The levels of E2 in the tissues of early abortion, peripheral blood of pregnant women and umbilical artery blood, placenta tissue of the women during labor were measured by chemiluminescence immunoassay(CLIA). After BeWo cells in monolayer culture, those cells were treated with E2 of 0 mol/L, 5×10-7 mol/L, 5×10-8 mol/L and 5×10-9 mol/L for 1, 3, 6 and 12 h, and then transepithelial resistance (TEER) was measured by millicell ESR-2 to observe the integrity of the tight junctions between BeWo cells.　Results：E2 were lower in peripheral plasma from early pregnancy[（3.44±1.30）nmol/L] compared with that from third trimesters[（509.78±197.82 ) nmol/L]（t=10.2,P＜0.001）. However, E2 were higher in tissue obtained from villus[（30.82±13.91） pmol/mg] than that from third trimesters placenta[（17.21±5.37）pmol/mg]（t=4.1, P＜0.001）. A decrease of TEER was observed after the treatmeat of E2 at a concentration of 5×10-7 mol/L for 12 hours(P＜0.05). The other two concentrations, 5×10-8 mol/L and 5×10-9 mol/L, had no significant effect on the TEER of BeWo cells at all time points(P＞0.05). Conclusions： The concentrations of E2 in villus obtained from first trimester is higher; E2 in full-term birth placenta tissues is relatively lower; In vitro, different concentrations of E2 may affect the maintenance of junction between trophoblast cells, 5×10-7 mol/L can be used as the effective concentrations of estradiol to treat with BeWo cells.

Key words: Pregnancy, Chorionic villi, Placenta, Estradiol, Pregnancy, Chorionic villi, Placenta, Estradiol