JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):134
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263769

P-122. ICSI vs. IMSI: A Prospective Paired Study Comparing Embryo Quality and Morphokinetics in Couples with Male Factor Infertility

Martina Caroline Stapenhorst¹, Thiago A C L Lofti¹, Ana Carolina Cardillo Fernandes¹, Andrea Belo¹, José Roberto Alegretti¹, Dóris Spinosa Chéles¹, Mauricio Barbour Chehin¹, Aline Rodrigues Lorenzon¹, Paula Intasqui²

¹ Huntington Medicina Reprodutiva - Eugin Group - São Paulo – SP -Brasil
² Departamento de Cirurgia - Disciplina de Urologia - Universidade Federal de São Paulo/UNIFESP - São Paulo - SP - Brasil

Objective: Intracytoplasmic sperm injection (ICSI) is the standard Assisted Reproduction Technique (ART) for treating male factor infertility, allowing fertilization despite low sperm concentration, motility, or morphology. To enhance sperm selection, intracytoplasmic morphologically selected sperm injection (IMSI) was developed, employing high-magnification microscopy to exclude sperm with subtle morphological defects. Although IMSI may benefit selected cases — such as those with severe teratozoospermia — evidence of its advantage over ICSI remains inconclusive, and its use is limited by technical complexity and time requirements. Thus, this study aimed to compare embryo development outcomes in couples with male infertility undergoing ICSI and IMSI in the same cycle.
Methods: A prospective, paired study was conducted with 18 couples meeting the following clinical inclusion criteria: female age between 35 and 42 years, at least six mature oocytes (metaphase II, MII), and male partners diagnosed with oligoasthenoteratozoospermia (sperm concentration ≤16million/mL, progressive motility ≤30%, and Kruger morphology ≤1%), moderate oligoteratozoospermia (concentration ≤5million/mL and morphology ≤1%), severe oligozoospermia (≤1million/mL), or isolated teratozoospermia (Kruger morphology <1%). Controlled ovarian stimulation was performed using GnRH agonist or antagonist protocols, and oocyte retrieval occurred 36 hours after triggering. Semen samples were collected on the day of retrieval and prepared using standard laboratory techniques (discontinuous density gradient, gradient + swim-up, or ZyMÖT^®), according to semen quality. After denudation, MII oocytes were randomly divided into ICSI and IMSI groups, with a minimum of three oocytes per group. If the number of oocytes was odd, the extra oocyte was randomly assigned and alternated between patients. ICSI was performed at 200x–400x magnification, while IMSI was performed at 6300x magnification, selecting classes I or II sperm. Embryos were cultured predominantly in a time-lapse incubator (EmbryoScope Plus^®, Vitrolife). Outcomes compared between groups included fertilization rate, top-quality embryos on Day 3, blastocyst development, top-quality blastocysts, ploidy, and morphokinetics (tPNf, t2, t3, t4, t5, t8, and tB). Statistical analysis was conducted using the paired Wilcoxon test, with significance set at p<0.05.
Results: The mean male and female ages were 40.7±5.3 and 37.3±3.3 years, respectively. A total of 228 MII oocytes were collected (mean: 12.4±6.7 per patient), evenly allocated to ICSI (n=114) and IMSI (n=114). Fertilization rates were similar between ICSI and IMSI (78±17% vs. 74±20%; p=0.44). The rate of top-quality Day-3 embryos was significantly higher with ICSI (77±26% vs. 58 ± 34%; p=0.023). No significant differences were observed in blastocyst formation (56 ± 33% vs. 42±27%; p=0.13), top-quality blastocyst rates (82±33% vs. 75±35%; p=0.61), or ploidy status (32±38% vs. 32±39%; p=0.77). Morphokinetics data were available for 88.8% of embryos. Embryos derived via ICSI showed significantly shorter time to pronuclear fading (tPNf) by approximately one hour compared to IMSI (24.41±2.95 vs. 25.63±3.64 hours; p=0.048). No significant differences were found in other developmental timepoints.
Conclusion: In this prospective paired study, ICSI and IMSI yielded comparable outcomes in fertilization, blastocyst development, and embryo ploidy among couples with male factor infertility. However, ICSI was associated with a higher rate of top-quality Day-3 embryos and a shorter tPNf, indicating potentially faster early embryonic development. These findings support the continued use of ICSI as an effective and efficient standard approach for male infertility, while suggesting that the clinical benefit of IMSI warrants further investigation.