Estradiol is an estrogen secreted by the follicles and the level of estradiol can indicate the quality of the follicles. In general, the quality of follicles during ovulation is better than during other periods. Estradiol values range from 1100-1500 pmol/L for one good quality follicle during ovulation, and may reach 3670 pmol/L or more for three or four follicles at a time. The value of estradiol is not the only indicator of good or bad follicles, but should be determined by ultrasound examination in conjunction with the size and morphology of the follicles, which are of good quality when they are of appropriate size and mature. Under normal circumstances, the normal range of estradiol in women varies from time to time, usually the normal range of estradiol in normal women is 90-280pmol/L during follicular phase, 734-2202pmol/L during ovulation, 367-1101pmol/L during luteal phase and 18-92pmol/L during menopause. Estradiol values in women below 90pmol/L often indicate primary or secondary ovarian insufficiency or menopause, etc., and above 280pmol/L indicate anovulatory functional uterine bleeding, ovarian tumors, etc. The normal value ranges or units of different laboratories are not entirely consistent and need to be interpreted in conjunction with the normal value ranges provided in the report forms. If a woman is preparing for pregnancy through normal sexual intercourse, it is not necessary to test the value of estradiol, because generally estradiol increase only occurs for 2 days and it is not easy to monitor, just relax and prepare for pregnancy normally.