Piezo-ICSI Reduces Oocyte Degeneration, Improves ICSI Success Rates and Has Shown Less Dependence on the Experience Level of Embryologists: Cumulative Data with 65,033 MII Oocytes

Introduction: Recent improvements in mercury-free piezo-assisted intracytoplasmic sperm injection (P-ICSI) devices have renewed interest in this technique, and reports on its usefulness are increasing. Aims: This study compares laboratory outcomes of P-ICSI and conventional ICSI (C-ICSI) and examines whether results differ by maternal age or embryologist experience. Methods: This retrospective observational cohort study included all eligible oocyte retrieval cycles performed at a single high-volume assisted reproductive technology (ART) centre (Sugiyama Clinic Shinjuku) from January 2018 to February 2023 after prespecified exclusions. A total of 15,687 cycles yielded 65,033 mature metaphase II (MII) oocytes. C-ICSI was performed from 2018 to early 2019, and P-ICSI was introduced in 2019. Outcomes included fertilisation per MII oocyte, post-ICSI oocyte degeneration and blastocyst formation per fertilised oocyte. Prespecified subgroup analyses were performed by female age ([Formula: see text]40 vs [Formula: see text]40 years) and embryologist experience (senior [Formula: see text]10 years; intermediate 5–10 years; junior [Formula: see text]5 years). Results: Amongst 65,033 MII oocytes, 13,549 underwent C-ICSI and 51,484 underwent P-ICSI. Compared with C-ICSI, P-ICSI was associated with a higher fertilisation (83.8% vs 74.8%; [Formula: see text]), lower degeneration (2.9% vs 6.9%; [Formula: see text]) and higher blastocyst formation (54.0% vs 36.3%; [Formula: see text]). These advantages persisted in women aged ¡40 years (fertilisation 84.6% vs 75.9%; degeneration 2.8% vs 6.8%; blastocyst 58.9% vs 42.0%; all [Formula: see text]) and [Formula: see text]40 years (82.6% vs 72.8%; 3.0% vs 7.1%; 46.9% vs 25.8%; all [Formula: see text]). With C-ICSI, fertilisation decreased with less experience (77.2%, 70.6% and 63.8%; [Formula: see text]), whereas fertilisation remained stable with P-ICSI (82.2%, 82.0% and 82.2%). Conclusions: P-ICSI is associated with improved fertilisation and blastocyst formation and reduced oocyte degeneration compared with C-ICSI, with consistent benefits across maternal age strata and reduced dependency on operator experience. These findings support broader adoption of P-ICSI as a gentler and more reproducible micromanipulation technique.