RESUMO
OBJECTIVE: To investigate endometrial receptivity (ER), conception outcome, and other factors among women with light menstrual bleeding of unidentified etiology. METHODS: A prospective study was undertaken at a center in China. Between January 1, 2011, and December 31, 2014, women meeting the inclusion criteria (aged 20-35 years, without any history of pregnancy, desire to conceive, follicle-stimulating hormone <10 IU on second or third day of cycle, and regular menstrual periods) were enrolled. Participants with a menstrual blood volume of 5-20 mL formed the study group; others were in the control group. ER measures were obtained by transvaginal Doppler ultrasonography. Serum estradiol and progesterone levels were measured and items of prethrombotic state were screened in mid-luteal phase. Participants were followed up for 1 year to establish conception outcome. RESULTS: The ER (Salle) score was significantly lower in the study group (n=110) than in the control group (n=330; 9.41 ± 3.02 vs 15.67 ± 2.63, P<0.001). The natural rate of conception within 1 year was lower (60.0% [63/105] vs 72.1% [230/319], P=0.020), and the spontaneous abortion rate in early pregnancy was higher (34.4% [21/61] vs 18.1% [41/227], P=0.006) in the study group than in the control group. CONCLUSION: Women with light menstrual bleeding of unidentified etiology had an increased prevalence of low ER and poor conception outcome.