O-052 Morphometric and morphokinetic differences in the sperm- and oocyte- originated pronuclei of male and female human zygotes: a time-lapse study

Abstract Study question Do morphometric and morphokinetic profiles of pronuclei (PN) following intracytoplasmic sperm injection (ICSI) vary between male female human zygotes? Summary answer Male zygotes displayed different PN morphometrics morphokinetics. Additionally, variations were identified sperm-originated (SPN) oocyte-originated (OPN) pronuclei. What is known already Previous studies have investigated the use PN-associated parameters via static observations as indicators zygote viability, including size equality or juxtaposition. However, recent clinical application time-lapse videography (TLV) provides a novel opportunity to assess these pronuclear events with greater accuracy precision measurement. A number TLV also potential live birth prediction by such associated measures, however whether not there are sex differences in measures which could turn confound unknown. design, size, duration This retrospective cohort study included 94 consecutive autologous single day 5 transfer cycles (either fresh frozen) performed January 2019 March 2020. Only ICSI (maternal age <40 years) leading singleton (43 males 51 females) for analysis. All oocytes placed EmbryoScope incubator culture immediately post all annotation retrospectively one embryologist (L-SO). Participants/materials, setting, methods Timings 2nd polar body extrusion (tPb2), SPN(tSPNa)/OPN(tOPNa) appearance (differentiated proximity Pb2) fading (tPNF). Morphometrics evaluated at 8 (stage 1), 4 2) 0 hour before PNF 3), measuring area (um2), juxtaposition, nucleolus precursor (NPB) arrangement. Means ± standard deviation compared using student t test logistic regression odds ratio (OR) 95% confidence interval (CI), proportional data chi-squared Main results role chance Logistic indicated that had longer time intervals tPb2_tSPNa than (4.8±1.5 vs 4.2±1.0 h, OR = 1.442, CI 1.009-2.061, p 0.044), but tPb2_tOPNa (4.7±1.8 4.5±1.3 1.224, 0.868-1.728, 0.250) tPb2_tPNF (19.9±2.8 19.1±2.3 1.136, 0.957-1.347, 0.144). SPN increased from stage 1 through 2 3 (435.3±70.2, 506.7±77.3, 556.3±86.4 um2, 0.000) OPN did similarly (399.0±59.4, 464.3±65.2, 513.8±63.5 0.000), being significantly larger each (p < 0.05 respectively). relative difference was similar stages (33.6±61.7 38.6±50.8 0.664; 38.5±53.1 45.7±71.9 0.585; 38.4±77.4 45.8±63.9 0.615; More reached central juxtaposition (77% 51%, 0.010), (98% 86%, 0.048) 0.048). Furthermore, more showed aligned NPBs (45% 29%, 0.023), proportions (64% 50%, 0.056) (76% 72%, 0.618). There no detected NPB alignment either > Limitations, reasons caution The design does allow control unknown confounders. Sample considered relatively small. measurement may truly represent volume be perfectly spherical. Findings based on women years old so apply older population. Wider implications finding These findings augment extend previous investigating observations. reported embryos when Larger scaled warranted verify findings. funding/competing interest(s) N/A. Trial registration