Clinical Significance. Measuring the circulating levels of estradiol is important for assessing the ovarian function and monitoring follicular development for assisted reproduction protocols. Reference Values For Estradiol Pregnancy. References: Oxis Estradiol (E2) Enzyme Immunoassay Test Kit Package Insert (PDF) Describes how estrogen (estrone, estradiol, estriol) tests are used, when estrogen tests are ordered, and what the results of an estrogens test might mean Estradiol levels are measured in women to assess their reproductive function and health. The Centre for Menstrual Cycle and Ovulation Research is the only centre in the world that focuses on ovulation and the causes for and health consequences of ovulation disturbances. Our goal is to do good science that honours the voices and experience of women. Estradiol (E2) levels below the premenopausal reference range in young females indicate hypogonadism. If luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels are elevated, primary gonadal failure is diagnosed. To investigate how late-midluteal estradiol levels relate to the pregnancy outcome in IVF cycles, and to assess whether human chorionic gonadotropin (hCG) for luteal support benefits the pregnancy outcome of patients with low late-midluteal estradiol Adding Estrogen to Progesterone in Luteal Phase Support in In Vitro Fertilization-Embryo Transfer (IVF-ET) Cycles Produces Pregnancies with Higher Quantitative Beta Human Chorionic Gonadotropins (βhCG) Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous and menstrual female reproductive cycles. The four major naturally occurring estrogens in women are estrone (E1), estradiol (E2), estriol (E3), and estetrol (E4). Estradiol is the predominant estrogen during reproductive years both in terms of absolute serum levels as well as in terms of estrogenic activity.