Stimulation day-six serum estradiol: a predictive indicator for the probability of embryo cryopreservation in IVF/ICSI cycles

Objective: To evaluate the predictive value of stimulation day six serum estradiol (E2) for the probability of embryo cryopreservation after fresh embryo transfer in intracytoplasmic sperm injection (ICSI) cycles. Subjects and Methods: The study included 282 ICSI cycles for different causes of infertility, provided that the age of the female partner was <40 years and her basal follicle stimulating hormone <10 IU/L. Setting: Alexandria IVF/ICSI center. Main Outcome Measures: Primary outcome measures are stimulation day-six serum E2, and rate of embryo cryopreservation, after transfer of three good-quality embryos. Secondary outcome measures are pregnancy rate per fresh embryo transfer, and other intermediate variables of the ICSI cycle. Results: Patients were stratified into three groups according to day-six serum E2 levels: Group I with values <400 pg/mL; Group II, between 400 and 900; and Group III with values >900. The mean number of oocytes retrieved was 6.3, 8.9, and 12.4; the mean number of obtained embryos was 3.3, 4.8, and 6.7; and pregnancy rates were 18.1, 36.2, and 44.7% in the three groups, respectively. Rate of embryo cryopreservation, after transfer of three good-quality embryos was 70.7% in Group III, and 26.5% in Group I. (P = 0.01). The negative predictive value of day-six E2 < 400 pg/mL for freezing was 83% while day-six serum E2 > 900 pg/mL has a sensitivity of 55%, specificity of 72% and positive predictive value of 50% for embryo freezing. Conclusion: Higher stimulation day-six estradiol was associated with a higher probability of cryopreservation, and a higher pregnancy rate.