Limiting the number of fresh donor oocytes inseminated with sperm as a strategy to minimize supernumerary embryos.

Objective: To determine the optimal number of fresh donor oocytes to expose to sperm for patients who want to prioritize reducing surplus embryos while preserving the live birth rate.

Design: Cross-sectional study.

Setting: University.

Patient(s): Patients who underwent their first in vitro fertilization of fresh donor oocytes at a single academic institution between January 2013 and November 2022. Patients were excluded if they used a directed oocyte donor, donor aged >32 years, gestational carrier, surgically retrieved sperm, or preimplantation genetic testing.

Intervention(s): Number of fresh mature donor oocytes fertilized via intracytoplasmic sperm injection.

Main outcome measure(s): The primary outcome was the number of cryopreserved supernumerary blastocysts. The number of supernumerary blastocysts was defined as the number of blastocysts remaining after the first live birth, or if the patient did not have a live birth, the number of supernumerary blastocysts was determined by the number of blastocysts remaining after the last transfer cycle. The Kruskal-Wallis rank sum test was used to determine differences in number of supernumerary blastocysts.

Result(s): A total of 543 patients who underwent 750 embryo transfer cycles using fresh donor oocytes were included. The average recipient age was 42.9 ± 3.8 years, and the average oocyte donor age was 26.6 ± 3.0 years. For our cohort, patients received a median of 10 (interquartile range [IQR], 8-14) mature donor oocytes; 8 (IQR, 6-11) were injected with sperm, 4 (IQR, 3-6) usable embryos were developed, and 2 (IQR, 0-5) supernumerary blastocysts remained. Patients were then divided into four quartiles on the basis of the number of mature donor oocytes received (≤7, 8-10, 11-14, or ≥15). There was a significant increase in the median number of cryopreserved supernumerary blastocysts as the number of mature donor oocytes exposed to sperm increased (1 vs. 2 vs. 3 vs. 6 blastocysts in the first, second, third, and fourth quartiles, respectively). There were no statistically significant differences in live birth rates between the quartiles.

Conclusion(s): The number of supernumerary blastocysts significantly increased as more mature donor oocytes were exposed to sperm. This study can serve as a counseling tool for patients with concerns regarding excess cryopreserved embryos when using fresh donor oocytes.