Can the peak E2/follicle ratio be a quantitative indicator of pregnancy outcomes following assisted reproductive cycles? A retrospective study.

As one of the limited reference parameters for the appropriate timing of human chorionic gonadotropin (hCG) priming and embryo transfer (ET), peak serum estradiol (E2) level and related parameters have been considered to be a possible marker of in vitro fertilization (IVF) outcomes. To our knowledge, few reports have investigated the correlation between the ratio of peak serum E2 to the number of follicles ≥ 14 mm on the day of hCG administration (i.e., the E2/fol. ratio) and the miscarriage rate (MR) in assisted reproductive cycles. In this study, a total of 1376 cycles were examined and grouped into quartiles by E2/fol. ratio. The patient characteristics, controlled ovarian hyperstimulation (COH) performance, and IVF/ICSI results were compared between the four groups. Patients were further categorized as younger than 35 years of age or 35 years of age and older. The association between the E2/fol. ratio and the implantation rate (IR) or MR was examined using the Mantel-Haenszel test for each group. We found that the E2/fol. ratio correlated with the IR and MR for women younger than 35 years of age. There was a statistically significant increase in the IR with E2/fol. ratio between 279.83 and 552.28 pg/ml, and women with an E2/fol. ratio > 552.28 pg/ml were more likely to suffer miscarriages. Our data support a role for cryopreservation of all embryos when E2/fol. ratio exceeds 552.28 pg/ml for women younger than 35 years of age.