O-079 Perinatal and postnatal outcomes up to the third year of life after the transfer of mosaic embryos compared with euploid embryos
Authors: Morales Sabater R , Lledo B , Ortiz J A , Arenas L , Bernabeu A , Castillo J C , Bernabeu R 
Published: June 2023

Abstract

Study question
Are perinatal and postnatal outcomes different following the transfer of blastocysts diagnosed as low-grade mosaic compared to euploid embryos?

Summary answer
Our study did not show any significant difference between children conceived after transferring low-grade mosaic versus euploid embryos regarding perinatal outcomes and physical health.

What is known already
A considerable percentage of embryos are classified as mosaic in IVF-cycles with preimplantation genetic testing for aneuploidy (PGTA). Although societies, such as Preimplantation Genetic Diagnosis International Society (PGDIS), have proposed recommendations for the transfer of these embryos, there is no worldwide consensus on the classification, especially in terms of the level of mosaicism, and their clinical management. There are studies on clinical outcomes in terms of implantation and pregnancy, and some of them have reported the birth of healthy children. However, studies evaluating perinatal outcomes and, physical health and development during childhood are limited.

Study design, size, duration
This retrospective cohort study includes 172 children born after the transfer of a single embryo analysed with PGT-A using next-generation sequencing (NGS), between October-2017 and August-2022. Children were divided into two groups, according to whether they were classified as euploid (n = 115) or mosaic embryo (n = 57) after PGT-A. All mosaic embryos carried a level of mosaicism below 50%. Data related to the level of mosaicism, number of chromosomes involved or type of alteration were reviewed.

Participants/materials, setting, methods
This study analyses clinical parameters/outcomes during gestation, birth and postnatal period, including prenatal test, pregnancy and delivery complications, type of delivery, breastfeeding, incubator/neonatology stay, congenital anomalies, maternal and gestational age, birth weight, height and head circumference, Apgar-score and health problems or chronic diseases until today. The oocyte/sperm age and their origin were also analysed. The differences between groups were evaluated by R (4.2.0). In children from mosaic embryos, postnatal karyotyping was offered to the parents.

Main results and the role of chance
According to mosaicism characteristics, 61.4% of embryos had 25-39% of mosaicism and 38.6% had 40-50%, 82.5% had one chromosome affected and 17.5% two chromosomes. No significant differences were observed between the euploid and mosaic groups in pregnancy and delivery complications, type of delivery and gestational age (39.22±1.92 weeks in euploid group vs 39.00±1.78 in mosaic), however maternal age was higher in mosaic group (40.07±3.32y vs 38.27±3.06y, p &lt; 0.001). Regarding newborn parameters, no differences were reported in birth weight, height and head circumference in euploid group compared to mosaic group (3222±581 vs 3227±530g, 49.92±2.67 vs 50.13±2.65cm, 34.50±1.87 vs 34.50±1.86cm; p &gt; 0.05), neither in the Apgar-score (8.58±2.48 vs 8.96±1.79, p &gt; 0.05) nor in the incubator/neonatology stay. With regard to congenital anomalies, their incidence was similar in both groups (8.7%, euploid vs 7.0%, mosaic) and in all cases were minor anomalies. No health problems/chronic diseases were recorded in either group, with the average age of the child at present being 3.48±0.81y in euploid group and 2.92±1.32y in mosaic. Prenatal testing was higher in the mosaic group, being carried out in 49.1% of pregnancies (23 non-invasive test and 4 amniocentesis) with normal result. Moreover, postnatal karyotype was performed in 6 children from mosaic group with normal result.

Limitations, reasons for caution
This study was limited by the sample size. Further larger studies are needed to ensure that the health outcome of children conceived after low-grade mosaic embryo transfer is comparable with children conceived after euploid embryo transfer.

Wider implications of the findings
Data following the transfer of blastocysts diagnosed as mosaic remain limited, especially in terms of neonatal/early-childhood outcomes. Our study suggests that the transfer of low-grade mosaic embryos lead to healthy children and provides further perinatal and postnatal clinical data. The normal prenatal/postnatal karyotype in the analyzed cases provides further reassurance.

Trial registration number
Not applicable