Received April 10, 2023
Accepted October 21, 2023

Introduction: Recently, it has been discussed whether or not mosaic embryo transfer should be performed, since it could result in viable pregnancies, but often end up being discarded. We report a successful pregnancy, after mosaic embryo transfer from an in vitro matured egg and frozen PESA sperm. Case Description: Female, 40 years, and male, 37 years, assessing fertility. The ovarian reserve testing was adequate, pervious fallopian tubes. He had a history of cryptorchidism and inguinal hernia repair. The spermogram showed azoospermia, and testicular ultrasound showed atrophic left testicle, normal right testis. Deferens palpated in physical examination. Intracytoplasmic sperm injection with percutaneous epididymal sperm aspiration (PESA) was indicated. Two cycles of IVF after controlled ovarian stimulation with deltafollitropin was performed. In the first cycle, seven mature eggs were inseminated, 2 fertilized normally, resulting in 1 blastocyst biopsied and analyzed by NGS with complex aneuploid results. In the second cycle, frozen sperm from PESA was used. Three eggs were inseminated on the procedure day (resulting in 2 blastocysts), and 3 in vitro matured eggs inseminated after 24 hours (resulting in 1 blastocyst). The NGS analysis showed two complex aneuploid embryos, and one 40% low-level trisomy 20 aneuploid mosaicism (+20) for the post 24 hour embryo. Mosaic embryo transfer was performed, resulting in clinical pregnancy and birth of a healthy baby girl with a normal blood karyotype. Discussion: Mosaic embryo transfer is a topic for discussion. Certain levels of mosaicism don't seem to pose any risk to the development of the fetus.