Strengths and Limitations
To our knowledge, this study is the largest to evaluate the clinical usefulness of ERA for RIF patients. However, its retrospective nature and strict inclusion criteria for defining subpopulations mean that some comparisons were carried out with moderate sample sizes and a limited number of transferred embryos. This particularly affected the S-RIF PGT-A, ERA, and PGT-A+ERA subgroups. From a clinical perspective, this affects how the data should be interpreted. When comparing M-RIF subgroups, our study was powered to detect a 10% effect of using ERA results to guide ET. For the S-RIF subgroups, which had even lower numbers of patients, our study was powered to detect an approximate 20% effect. Our work is underpowered for confirming smaller differences. As more data is collected, some clinical benefit of the test might be detected, but our research indicates that any beneficial effect of PGT-A in S-RIF patients is limited.