P–520 Live birth rate with a euploid embryo is the same irrespective of the number of oocyte retrievals undertaken to produce a euploid embryo
Authors: Theodorou E , Cardena. Armas D , Jones B P , Serhal P , Ben-Nagi J 
Published: August 2021

Abstract

Study question
Does a euploid embryo from one ovarian stimulation lead to the same live birth rate as a euploid embryo arising from multiple ovarian stimulations?

Summary answer
The live birth rate of a euploid embryo transferred is comparable irrespective of the number of ovarian stimulations required.

What is known already
Embryo transfer of a euploid embryo leads to a high live birth rate. Women with low ovarian reserve or poor responders may not have a euploid embryo from one cycle of ovarian stimulation and can be discouraged from undergoing preimplantation genetic testing for aneuploidy (PGT-A). Embryo batching from multiple cycles offers such patients a potential solution to increase their chance of achieving a euploid embryo.

Study design, size, duration
A retrospective analysis of 506 cycles of single euploid frozen embryo transfers (FET) from January 2015 to March 2020 was carried out. The indication for PGT-A was advanced maternal age, recurrent miscarriages or repetitive IVF failures. Only the first single euploid FETs per patient were included.

Participants/materials, setting, methods
Group A (N = 323) included women who had a normal ovarian reserve and only one cycle of ovarian stimulation before the FET, whilst Group B (N = 183) had low ovarian reserve or previous poor ovarian response requiring 2 or more cycles of ovarian stimulation. All embryos were biopsied at the blastocyst stage and subjected to a-CGH or NGS. Univariate statistical analysis with Chi-square or Wilcox Man U as required and multivariate logistic regression was performed with SPSS.

Main results and the role of chance
Group A and Group B were comparable in terms of BMI (average 22.3 vs 22.6), sperm origin, number of blastocysts biopsied (median N = 6, range 4–8), day 5 vs day 6 biopsy (day 5, 81.1% vs 75.4%, p = 0.130) and whether only one euploid embryo was available (42% vs 34%; p = 0.103). There was a significant difference in the number of eggs retrieved per cycle between the two groups (median 15 vs 9, p &lt; 0.001), the total number of eggs retrieved (median 15 vs 20, p &lt; 0.001) and whether a top-quality embryo was transferred (38% vs 25%, p = 0.026). Pregnancy rate, live birth rate and pregnancy loss was equivalent for both groups: 69.3% (224/323) vs 63.9% (178/183) (p = 0.212), 57.6% (186/323) vs 57.4% (105/183) (p = 0.096) and 17.0% (38/224) vs 10.3% (12/117) (p = 0.964), respectively.
Multivariate logistic regression was performed to ascertain the effect of the treatment variables on the live birth rate. The number of oocyte collections was not a significant predictive factor (OR 1.19, 95% CI 0.72 - 1.96, p = 0.491), whilst an embryo biopsy performed on day 5 vs day 6, increased significantly the live birth rate (OR 2.58, 95% CI 1.61 - 4.13, p &lt; 0.001).

Limitations, reasons for caution
The main limitation of this study is that it is retrospective, single centre and therefore vulnerable to confounding factors and bias.
Wider implications of the findings: These results can be used to counsel and reassure women with poor response embarking on embryo batching and PGT-A that should a euploid embryo become available, their chance of success is unaffected by the number of cycles they undertake albeit the physical, emotional and financial burden of multiple ovarian stimulations

Trial registration number
Not applicable