P-422 A retrospective cohort study on the usefulness of Endometrial Receptivity Analysis (ERA) prior to a gestational carriers’ (GC) first euploid frozen embryo transfer (FET)
Authors: Royster G.D , Anderson R 
Published: June 2022

Study question

Does determination of endometrial receptivity by ERA improve the outcome of FET for GC prior to their first FET using a euploid embryo?

Summary answer

GC with ERA prior to FET had 92.3% implantation and 84.6% live birth rate (LBR) compared to 81.5% implantation rate and 72.2% LBR without ERA.

What is known already

The endometrial window of implantation is approximately 24 hours wide with a complex interaction of autocrine, paracrine and endocrine factors. Successful embryo implantation involves a 3-step process of apposition, adhesion and invasion of an embryo into a receptive endometrium. The ERA was developed using the expression profile of 248 genes using Next Generation Sequencing to determine if the endometrium is receptive, early receptive, late receptive, pre-receptive or post-receptive to objectively determine the optimal timing of progesterone exposure prior to embryo transfer. Some studies have shown statistically significant improvements in live birth rates while other studies have shown no difference.

Study design, size, duration

A retrospective cohort study compared the implantation and live birth rates of 26 GC who chose to have a personalized embryo transfer using their ERA profile vs. 54 GC who used our standard FET protocol without an ERA prior to their first euploid FET. All GC having their first FET from January 2018 – December 2020 were included.

Participants/materials, setting, methods

A single private practice fertility clinic performed 80 euploid FET cycles on first-time GC from January 2018 – December 2020. All intended parents were offered the opportunity to complete an ERA for their GC prior to their first FET cycle. Implantation and live birth rates were calculated for all FET cycles using a GC for the first time with associated p – values.

Main results and the role of chance

GC were 22 – 38 years old with a mean age of 30 and a history of 2.4 previous spontaneous births prior to their first FET. GC who used a standard FET protocol with 5 days of progesterone (P + 5) exposure before FET had an implantation rate of 81.5% and a live birth rate of 72.2%, compared to an implantation rate of 92.3% and a live birth rate of 84.6% for GC who used a personalized embryo transfer protocol based on their ERA profile (p = 0.17). 19.2% of GC had a receptive endometrial profile using P + 5, 26.9% of GC were pre-receptive needing P + 5.5 and 53.8% needed P + 6. No GC were found to have a post-receptive endometrial profile (P + 4 or P + 4.5). Our retrospective cohort study was not powered to find a statistically significant difference, though our data trended towards an improvement in both implantation and live birth rates by over 10% if a GC were to complete an ERA prior to her first FET.

Limitations, reasons for caution

Implantation and live birth rates for the clinic during the study period were 75% and 68% respectively using euploid embryos. Our high baseline implantation and live birth rates, coupled with low numbers of patients included in this study, may make these results less generalizable to the IVF population at large.

Wider implications of the findings

It is controversial to recommend an ERA to a good prognosis patient such as a GC without a prior unsuccessful euploid FET. These results should prompt further study to confirm our findings with a larger prospective randomized controlled trial of gestational carriers using ERA profiles prior to their first FET.

Trial registration number

N/A