Roles of estradiol levels on the day of human chorionic gonadotrophin administration in the live birth of patients with frozen embryo transfer.

Background: Estradiol (E ) is an important hormone in women. Changes of serum E levels may affect the endometrial receptivity for embryo implantation and thus affect pregnancy outcomes. This study was to assess the association between serum E levels on the day of human chorionic gonadotrophin (HCG) administration and live-birth rates in patients with frozen embryo transfer (FET).

Methods: Totally 2071 women receiving long protocols of long-acting gonadotropin-releasing hormone (GnRH) agonists were enrolled. According to the E levels on the day of HCG administration, these patients were divided into four groups: 676 cases of E  ≤ 3051 pg/mL in Q group, 676 cases of 3051 pg/mL < E  ≤ 4558 pg/mL in Q group, 675 cases of 4558 pg/mL < E  ≤ 6718 pg/mL in Q group, and 674 cases of E  > 6718 pg/mL in Q group. The clinical indicators including female age, body mass index (BMI), duration of infertility, infertility styles, treatment protocols, hormone levels, total antral follicle count, endometrial thickness, top-level embryos, and live-birth rates were analyzed, and multivariable logistic model was conducted to select significant variables.

Results: Significant differences were observed for the female age (OR = 0.965, 95% CI: 0.946-0.985, P < .001), total antral follicle counts (OR = 1.025, 95% CI: 1.008-1.043, P = .004), transferring what day of embryos (OR = 1.242, 95% CI: 1.137-1.356, P < .001), endometrial thickness (OR = 1.058, 95% CI: 1.004-1.115, P = .035), top-level embryos (OR = 1.416, 95% CI: 1.157-1.731, P = .001), and E levels on HCG day >6781 pg/mL (OR = 1.344, 95% CI: 1.069-1.690, P = .011) between live-birth and non-live-birth groups. The area under the curve (AUC) for E levels on HCG day was 0.558, the sensitivity was 54.75%, and the specificity was 55.10%.

Conclusion: Serum E level on HCG day was an independent predictor of live-birth achievement in patients with FET.