Estradiol is used in obstetrics to indicate the quality of embryo and evaluate the effect of fetal preservation, and in gynecology to determine the presence of precocious puberty, gynecological endocrine disorders and other diseases. 1. Obstetrics: Estradiol is mainly produced by the corpus luteum in the early stage of pregnancy and by the placenta after the formation of the placenta in the 12th week of pregnancy. The level of estradiol is indicative of the quality of the embryo, and regular monitoring of estradiol is recommended for patients who have a history of spontaneous abortion or symptoms of pre-eclampsia, and is one of the indicators for evaluating the effect of fetal preservation. 2. Gynecology: Estradiol is mainly used to promote the transformation of endometrium into proliferative state and the development of female secondary sexual characteristics. The normal value of estradiol varies in different periods of menstruation and different stages of life. It is mainly used to diagnose precocious puberty, gonadal dysgenesis, pubertal menstrual disorders, menopausal menstrual irregularities and gynecological endocrine diseases, and it can also be elevated in the case of ovarian tumors with endocrine function. If estradiol is found to be on the high or low side, it is recommended to consult a regular hospital in time for clear diagnosis and treatment under the guidance of professional doctors.