# Birth after low-level +20 Aneuploid Mosaic Embryo Transfer: A Case Report

## TL;DR

A healthy baby was born after a mosaic embryo with low-level trisomy 20 was transferred, suggesting some mosaic embryos can lead to successful pregnancies.

## Contribution

This case demonstrates that low-level aneuploid mosaic embryos can result in a viable, healthy pregnancy and live birth.

## Key findings

- A mosaic embryo with 40% trisomy 20 led to a successful clinical pregnancy and healthy baby.
- Low-level aneuploidy may not necessarily prevent normal fetal development.
- Mosaic embryos, previously considered high-risk, can produce viable offspring.

## Abstract

Recently, it has been discussed whether or not mosaic embryo transfers should
be performed since they might result in viable pregnancies, although they
often end up being discarded. We report a case of successful pregnancy,
after a mosaic embryo transfer from an in vitro matured egg and frozen PESA
sperm.

Tests performed on a female aged 40 years and a male aged 37 years seeking
fertility treatment found she had an adequate ovarian reserve and patent
fallopian tubes. He had a history of cryptorchidism and inguinal hernia
repair. The spermogram showed azoospermia, and testicular ultrasound showed
an atrophic left testicle and a normal right testis. The vas deferens was
palpated during physical examination. Intracytoplasmic sperm injection with
percutaneous epididymal sperm aspiration (PESA) was indicated. Two cycles of
IVF after controlled ovarian stimulation with follitropin delta was
performed. In the first cycle, seven mature eggs were inseminated, two
fertilized normally, resulting in one 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 day of the procedure
(resulting in 2 blastocysts), and three in vitro matured eggs were
inseminated after 24 hours (resulting in 1 blastocyst). NGS analysis showed
two complex aneuploid embryos and one 40% low-level trisomy 20 aneuploid
mosaicism (+20) for the post 24-hour embryo. A mosaic embryo transfer was
performed, resulting in clinical pregnancy and birth of a healthy baby girl
with a normal blood karyotype.

Mosaic embryo transfer is a topic for discussion. Certain levels of mosaicism
do not seem to pose risks to the development of the fetus.