Objective To explore predictive value of endometrial receptivity and pregnancy outcome by hysteroscopy examination at the phase of implantation window in unexplained infertile women.Methods From Oct.2007 to Mar.2009,93 unexplained infertile women underwent hysteroscopy examination at 7-9 days after a spontaneous ovulation in Family Planning Research Institute of Guangdong Province.According to the endometrial glandular openings and vascular shape,79 cases without pathological endometrial changes were divided into 60 cases in good endometrium group and 19 cases in poor endometrium group.The following clinical parameters were analyzed and compared between two groups,including endometrial configuration,thickness,secretion,the development and number of pinopodes,vascular distribution,and the level of sex hormone,leukemia inhibitory factor (LIF) and glycodelin in the uterine flushing,and pregnancy outcome.Results (1)There was no statistical difference in the level of serum estrogen and progesterone at the phase of implantation window,which were (518 ± 176)pmol/L,(40 ±20)nmol/L in good group and (513 ±244) ptnol/L,(37 ± 19) nmol/L in poor group (P<0.05).The endometrium thickness at periovulatroy and implantation window days (1.06 ±0.10)cm/(1.16 ± 0.08)cm in good group did not show significant difference with (0.93 ±0.12) cm /(1.02 ±0.10) cm in poor group (P>0.05).The proportion of type A,B and C endometrium at periovulatory days were 63% (12/19),37% (7/19) and 0 (0/19) in good group and 23% (14/60),77% (46/60) and 0 (0/60) in poor group.When compared with those of type A or B between two groups respectively,it all showed statistical difference (P<0.05).However,at phase of implantation window,endometrium configurations were all type B at both groups.(2)90% (17/19)of women in good group and 7% (4/60)of women in poor group showed normal endometrial secretion function,which showed significant differences (P< 0.01).(3)The percentage of fully developed pinopodes and abundant pinopodes [84% (16/19) and 90% (17/19)] in good group were significantly higher than 42% (25/60)and 57% (34/60) in poor group (P<0.05).(4) The level of CD_(34) expression and microvessel density[MVD; (40.1 ± 1.2) positive unit(PU) and(21.7 ±4.0)/high power field (HP)] in good group were significantly higher than(18.1 ± 1.3) PU and (8.5 ± 1.3)/HP in poor group (P< 0.01).(5)The level of LIF and glycodelin in uterine flushing [(72 ± 54)ng/L and (196 ±20)μg/L] in good group were significantly higher than (15±16) ng/L and (116 ±26) μg/L in poor group (P<0.05).(6) The rate of clinical pregnancy,spontaneous abortion and term delivery were 74% (14/19),0 (0/14) and 100% (14/14) in good group and 23% (14/60),14% (2/14) and 86% (12/14) in poor group,the rate of clinical pregnancy and term delivery in good group were significantly increased when compared with those in poor group (P<0.01).Conclusions Hysteroscopy examination at the phase of implantation window could reflect the development of glandular openings and vasculature.It is a preferable method to evaluate the endometrial receptivity and predict pregnancy outcome.