The numbers of biopsied cells in routine clinical process of preimplantation genetic testing (PGT) do not affect the pregnancy outcomes of embryos

STUDY QUESTION Does the number of biopsied trophectoderm cells sampled for preimplantation genetic testing for monogenic disease (PGT-M) affect subsequent clinical outcomes for those selected embryos? SUMMARY ANSWER The number of biopsied cells does not affect the pregnancy outcome of preimplantation genetically tested embryos. WHAT IS KNOWN ALREADY The successful execution of PGT relies on the availability of a certain number of high-quality biopsied cells. Evidence in the literature has reported that blastocyst biopsies may have a negative impact on clinical outcomes. STUDY DESIGN, SIZE, DURATION A retrospective cohort study including 850 single-blastocyst transfer cycles from 605 couples between May 2014 and August 2024 was conducted at Peking University Third Hospital. The primary clinical outcome measure was the biochemical pregnancy rate, while other indicators such as the live birth rate, the clinical pregnancy rate, and the miscarriage rate were also recorded. PARTICIPANTS/MATERIALS, SETTING, METHODS This study included 850 blastocysts obtained from routine PGT-M cycles. Based on biopsied cell numbers, data were categorized into four groups: Group 1 (1–5 cells) (n = 234), Group 2 (6–10 cells) (n = 328), Group 3 (11–15 cells) (n = 192), and Group 4 (>15 cells) (n = 96). MAIN RESULTS AND THE ROLE OF CHANCE The number of cells biopsied from the embryo did not significantly affect either the biochemical pregnancy rate or the live birth rate in the routine PGT process (P > 0.05). There were 129 of 234 embryos (55.1%) in the 1–5 biopsied cell group, 183 of the 328 embryos (55.8%) with 6–10 biopsied cells, 92 of 192 embryos (47.9%) with 11–15 biopsied cells, and 48 of 96 (50.0%) embryos with more than 15 biopsied cells which achieved successful pregnancies. The live birth rates were 42.7%, 49.7%, 43.2%, and 43.8% for each of the biopsy groups, respectively. LIMITATIONS, REASONS FOR CAUTION Data for this study were collected from one center only, therefore multicenter, large-scale cohort studies are essential to confirm the accuracy and the reliability of this study. WIDER IMPLICATIONS OF THE FINDINGS The number of biopsied cells in a blastocyst is associated with the embryo quality and hatching status. The conclusion of this study emphasizes that routine procedures during the biopsy process do not affect pregnancy outcomes. It is crucial to strike a balance between minimizing damage to the blastocyst’s developmental potential and achieving the highest possible detection efficiency for PGT-M. STUDY FUNDING/COMPETING INTEREST(S) This project is funded by the National Key Research and Development Program of China (2019YFA0801401, 2019YFA0110001) and the National Natural Science Foundation of China (82125013). The authors declare that they have no competing interests. TRIAL REGISTRATION NUMBER N/A.