What investigations are recommended after three failed embryo transfers?

The first step is arithmetic rather than investigation: what was the cumulative expected implantation probability across those three transfers? For a woman of 40 transferring untested cleavage-stage embryos, three failures may be entirely within expectation, and investigation would be premature. For a woman of 32 transferring good-quality euploid blastocysts, the same count is genuinely unexpected. Where investigation is warranted: Uterine cavity — hysteroscopy. The highest-yield single investigation, identifying polyps, adhesions, submucosal fibroids and septa. Chronic endometritis — endometrial biopsy with CD138 immunohistochemistry. Embryo and laboratory review — fertilisation rates, blastulation rates, grading trends, and whether laboratory KPIs are being met. Systematic laboratory issues present as multiple patients failing, so unit-level data matters here. Thyroid function and antiphospholipid antibodies. Sperm DNA fragmentation in selected cases. Consideration of PGT-A, with honest counselling about what it does and does not achieve. What should not be added routinely: endometrial receptivity testing, immunological panels and immunotherapy, inherited thrombophilia screening, endometrial scratch, intralipid, IVIG. Also reconsider protocol: endometrial preparation approach, luteal support adequacy, and transfer technique. These are less glamorous than added tests and more likely to be the issue.