Recruitment for the study
ENDOMETRIUM
Serum endocrine hormones including follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) were measured on days 2–4 of the menstrual cycle. EMT and endometrium type on ovulation day were also measured by transvaginal ultrasound. The day when the dominant follicle (≥18 mm) disappeared was defined as ovulation day. Endometrium with an EMT of less than 7 mm on ovulation day was considered thin. Only these patients were recruited for the study, i.e., randomly selected for the experimental group or for the control group.