P-755 Effect of female age and specific cycle characteristics on success in modified natural frozen-thawed single euploid embryo transfer cycles (mNC/FET)

Abstract

Abstract Study question Does the age of woman and specific cycle characteristics impact the success of modified natural frozen-thawed single euploid embryo transfer cycles (mNC/FET)? Summary answer The success rate of mNC/FET cycles is similar in all age groups. As the LH level increased ( above 23.5ng/dL) the success was significantly increased. What is known already The success of frozen embryo transfer can depend on various factors such as the patient’s age, the number of transferred embryos, the duration of embryo culture, and the method used to prepare the endometrium (Holschbach et al. 2023). However, there is currently insufficient evidence in the literature about the effect of age and cycle characteristics on the effectiveness of mNC/FET cycles in patients who have received single top and good quality euploid embryos. Study design, size, duration This study, conducted at Istanbul Memorial Hospital, ART and Reproductive Genetics Center, is a retrospective, single-centre analysis of 583 cycles of euploid mNC/FET in women aged 22-44 years. The study period was from July 2017 to January 2024. The cycles were divided into two groups based on the age of the women. Group A (n = 408) included women under the age of 38, while Group B (n = 175) included women aged 38 or above. Participants/materials, setting, methods The study investigated success predictors in mNC/FET with top and good-quality embryos. Excluded were women with recurrent pregnancy losses, recurrent implantation failure, high BMI (>35kg/m2), uterine/endometrial problems, severe male infertility, and autoimmune diseases. The mNC/FET success was a pregnancy lasting 12 weeks or more. The analysis included patient demographics and cycle outcomes. Chi-square, t-tests, and Mann-Whitney U tests assessed variables with a p-value < 0.005, indicating statistical significance. Main results and the role of chance No significant demographic differences were observed between the two groups, except for AMH levels. AMH levels were significantly higher in younger group than older group (3.02 ng/ml vs. 1.96 ng/ml, p = 0.000). The mNC/FET success rates were similar, with 76% in the younger group and 73% in the older group. Estradiol levels the day before trigger day were significantly higher in older group (278.02 pg/ml vs. 237.84pg/ml, p = 0.028). Both groups had similar mean LH levels (32.50 IU/L and 32.41 IU/L, respectively), estradiol levels and endometrial thickness on the trigger day. In the younger group, LH rise was observed later, follicular phase was longer, and embryo transfer day was later than the older group (p = 0.001). Univariate regression analysis revealed that increased LH level was an important independent variable in achieving mNC/FET success, with a 1.001-fold increase (p = 0.043). The LH levels of 23.5 IU/L or higher predicted high mNC/FET success with 60% sensitivity and 43% specificity based on the Receiver Operating Characteristic curve. (AUC: 0.606, %95 CI 0.540-0.671, p = 0.002). Prolonged infertility duration and previous ET failures reduced mNC/FET success by 0.889 and 0.544-fold, respectively (p = 0.002, p < 0.001). Higher β-hCG levels on days 14 and 16 increased mNC/FET success by 1.038-fold and 1.008-fold, respectively (p < 0.001). Limitations, reasons for caution Our study has limitations as it was retrospective. Prospective randomized studies are needed to evaluate the differences between the young (age <38) and old patient groups (age ≥38) based on mNC/FET success. The association between LH rise and mNC/FET success needs verification with a larger sample. Wider implications of the findings The mNC/FET success rates are similar in young (age <38) and old patient groups (age ≥38). However, prolonged infertility duration and previous failed ET cycles decreased the success of mNC/FET. Additionally, It is important to schedule trigger time after the optimum LH rise, which is 23.5 IU/L or higher. Trial registration number not applicable