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)

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

P-424 Endometrial receptivity as determined by Endometrial Receptivity Analysis (ERA) can change after a successful live birth from a frozen embryo transfer (FET)

Study question

Endometrial receptivity as determined by Endometrial Receptivity Analysis (ERA) can change after a successful live birth from a frozen a frozen embryo transfer (FET)

Summary answer

27 of 33 patients with a previous live birth from FET had an altered endometrial receptivity profile by ERA after a subsequent unsuccessful FET.

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

Case series of 33 patients with successful live birth following euploid FET using 5 days of progesterone (P + 5) with subsequent unsuccessful FET using the same protocol from January 2018 – December 2020. 27 of 33 patients who repeated their ERA were found to be non-receptive using P + 5. The new ERA profile results were used for their next FET. Implantation and live birth rates were calculated.

Participants/materials, setting, methods

A single private practice fertility clinic performed 340 ERA cycles from January 2018 – December 2020 with 276 subsequent FET cycles. An observational study of 33 patients with a previous live birth using P + 5 elected to repeat their ERA cycle after an unsuccessful FET. Implantation and live birth rates were calculated for their subsequent FET after completing the repeat ERA.

Main results and the role of chance

Repeat ERA result for patients with a previous live birth using P + 5 revealed that 6 patients still needed P + 5 (18.2%) for a receptive endometrial profile, 8 patients (24.2%) needed an extra 12 hours (P + 5.5), 18 patients (54.5%) needed an extra 24 hours (P + 6) and only one patient (3.0%) needed an extra 48 hours (P + 7). No patient that repeated their ERA after a previous live birth had a post-receptive profile (P + 4 or P + 4.5) and one patient had successful live births after using 3 different ERA profiles (P + 5, P + 6 and P + 7). All patients except one had repeat ERA results that were pre-receptive with only one patient changing from P + 6 to P + 5. FET cycles using P + 5 and P + 7 had a 100% implantation and pregnancy rate, while patients using P + 5.5 had the lowest implantation rate (62.5%) and live birth rate (37.5%). Patients with an ERA profile of P + 6 had an implantation rate of 94.1% and live birth rate of 88.2%. The small number of patients in this case series make a type I error possible because of the low number of patients in each ERA profile category with insufficient power to reach statistical significance.

Limitations, reasons for caution

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

Wider implications of the findings

It is widely accepted that ERA results are reproducible and do not change during a woman’s reproductive life. These results suggest that some women may have an altered window of receptivity after both successful and unsuccessful FET cycles. It may be reasonable to repeat ERA cycles for carefully selected patients.

Trial registration number

N/A