P-541 First live birth report of identical twins from a single low-grade mosaic blastocyst (46,XY/45,XY,-19) transfer: when a small chance becomes a double miracle
Authors: Matsumoto L , Cremonesi L  B , Brasileiro J  P B , Granjo F  I L , Rebello da Costa C , Rossine M  W S , Faria K  V M , Duarte-Filho O  B , Del Collado M 
Published: July 2024

Abstract

Study question
N/A

Summary answer
First live birth report of identical twins from the transfer of a single low-grade mosaic blastocyst for monosomy on chromosome 19.

What is known already
The clinical decision-making in cases involving the transfer of low-grade mosaic embryos remains controversial. Recent studies have indicated that low-grade mosaic embryos exhibit pregnancy rates similar to euploid embryos, encouraging their transfer. However, the judgment to proceed in most cases is still challenging. The transfer of a low-grade mosaic embryo for monosomy on chromosome 19 is considered relative safe. The occurrence of human twins resulting from embryo splitting in ART (Assisted Reproductive Technology) cycles is a rare phenomenon. To date, there are no reports of the birth of identical twins from a single low-grade mosaic embryo transfer.

Study design, size, duration
This is a single-case report detailing an assisted reproduction cycle conducted by a couple.

Participants/materials, setting, methods
A couple with a nine-year history of infertility, characterized by low ovarian reserve and azoospermia, underwent an ICSI (Intracytoplasmic Sperm Injection) cycle in October 2022. Due to azoospermia, microsurgical epididymal sperm aspiration and subsequent freezing of the retrieved sperm were performed prior to ovum pick-up. PGT-A (Preimplantation Genetic Testing for Aneuploidy) of the resultant blastocysts was conducted, followed by the transfer of a single low-grade mosaic after a modified natural endometrial preparation cycle.

Main results and the role of chance
Seven mature oocytes were retrieved, and following ICSI with the thawed seminal sample, four blastocysts were developed and biopsied for PGT-A analysis. Out of these four high-quality blastocysts, three were aneuploid, and the remaining one was a low-grade (50%) mosaic for monosomy on chromosome 19. After genetic counselling, the patients decided to proceed with the transfer of a day 5 3AA low-grade mosaic embryo, which led to a successful pregnancy. The transferred embryo split, generating a pregnancy of identical twins. The twins were delivered via cesarean section at 30 weeks and 5 days of gestational age. The premature delivery was necessitated due to the mother developing cardiac insufficiency related to pre-existing valvulopathy and a superimposed venous thromboembolism. Peripheral blood samples from the twins have been collected for a 100-cell karyotype analysis (results will be available by February 9th). This case marks the first reported instance of twins born from the transfer of a single low-grade mosaic blastocyst (46,XY/45,XY,-19).

Limitations, reasons for caution
This is a retrospective case-report from one couple, describing a rare event.

Wider implications of the findings
This case-report could elucidate the physician’s decision and slightly encourage the transfer of low-grade mosaic embryos when there are no full euploids available.

Trial registration number
Not pllicable