P-545 The age-related required number of zygotes estimated from prior clinical studies of preimplantation genetic testing for aneuploidy (PGT-A)
Authors: Mariya T , Sugimoto T , Miyai S , Kato T , Toshiaki E , Kurahashi H 
Published: June 2022

Abstract

Study question
How many eggs will be required to optimize the chances of a live birth with or without PGT-A?

Summary answer
The number of zygotes required for live birth is higher in women with an advanced age, and the use of PGT-A does not provide improvement.

What is known already
Women who are undergoing PGT-A often wish to know how many eggs will be required to optimize the chances of a live birth. This important information could be provided as part of prior genetic counseling, but there are no precise data on this at present. If the number of eggs required to give the best chance of a successful live birth was known, treatment plans with or without PGT-A could be better determined.

Study design, size, duration
We estimated the optimal number of eggs required for IVF treatment with PGT-A to produce at least a single live birth, stratified by maternal age, on the basis of information from prior studies and in current databases.

Participants/materials, setting, methods
We derived our calculation parameters from three prior large-scale clinical investigations associated with PGT-A. We estimated a live birth rate using the following factors: rate of zygotes that develop a useful blastocyst, euploid rate in PGT-A, and the live birth rate after euploid embryo transfer. All of these factors were assumed to be statistically independent in this study for the purposes of our calculations and the live birth rate per single zygote was calculated.

Main results and the role of chance
The estimations in our present analyses however indicate a probability of less than 10% that woman over 40 years of age will have a live birth from a single zygote, regardless of whether PGT-A is performed or not. We used a negative binomial distribution approach to calculate how many zygotes are needed to obtain at least one live birth. The plot of these results is provided in Figure 2. To achieve a 50% chance of getting at least one live birth, patients required 8 zygotes at age of 40 and 21 zygotes at the age of 43. Furthermore, to achieve an 80% chance of obtaining a live birth, our calculations estimate that 18 and 47 zygotes would be required at these two ages, respectively, which would be challenging to achieve. On the other hand, by avoiding unnecessary transplants using PGT-A, women may have to wait a shorter period to accomplish a live birth or may be able to avoid wasting their limited remaining reproductive period, particularly if they are older than 42.

Limitations, reasons for caution
The reference data from PGT-A studies that have estimated of the live birth rate include chromosomal quantitative PCR, microarray analysis, and next generation sequencing (NGS). There is a high possibility that the embryos designated as “euploid” in those studies include mosaic embryos, which represents a limitation of our present meta-analysis.

Wider implications of the findings
More details on the clinical outcomes of PGT-A will be revealed as clinical studies progress in the future. It is our hope that the results of this present study will assist with future genetic counseling strategies for PGT-A in the meantime.

Trial registration number
not applicable