To ascertain the predictive value of different parameters to determine endometrial receptivity among assisted reproduction treatments in which single embryo transfer of frozen-thawed euploid blastocysts are performed.
Observational study involving 104 patients recruited between September.2018 and June.2019 at a University associated assisted reproduction center. The relationship of different parameters (age, body mass index (BMI), duration of hormonal preparation, plasmatic progesterone levels, endometrial parameters at ultrasound assessment and endometrial receptivity determined by endometrial receptivity assay (ERA) was evaluated by a multivariable logistic (binomial) analysis after hormonal preparation. According to the ERA test results a personalized endometrial transfer (pET) was scheduled and live birth rate was assessed. Only single transfers of frozen euploid blastocysts were performed.
ERA test report predicted receptive endometrium (RE) in 54,64% patients and non-receptive (NR) in 45,31% patients. Among NR endometrial samples, 20,62% were classified as pre-receptive or early receptive, whereas 24,74% as post-receptive or late-receptive. The univariate analysis showed a relationship between BMI, doses of progesterone administered before biopsy and the receptivity of endometrium. There was no relationship between age of women, duration of hormonal supplementation, and the results of ERA test. In our series, endometrial receptivity was not related neither to endometrial thickness nor plasmatic progesterone levels. The multivariate analysis showed that both, BMI and cumulative progesterone administered prior to the test are independent predictive factors of endometrial receptivity (p = 0,047 and p = 0,034 respectively). The overall live birth rate after FET of euploid embryos was 62,35%. The odd of pregnancy was higher when ERA test was performed prior to the first embryo transfer (93,10% vs. 46,43%; OR = 15,58;95%CI 3,38-71,89). Overall, ongoing pregnancy rates showed a favorable trend after “non-receptive” endometria had been diagnosed and, thus, a modified (pET) preparation was performed (70,00% vs. 55,56%; OR = 1,87; 95% CI 0,76-4,57).
Regarding implantation potential of genetically screened blastocysts, the traditional tools used for assessing endometrial receptivity such as transvaginal evaluation of endometrial thickness and pattern or progesterone levels determination were not useful among our patients for predicting a receptive endometrium.

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