P-527 What is the influence of blastocyst hatching position on clinical pregnancy rates?

Abstract Study question Is there a relationship between the hatching zone in blastocyst and its gestational potential? Summary answer Blastocysts that presented area opposite to inner cell mass showed lower clinical pregnancy rates. What is known already Embryo implantation uterine endometrium dependent on out of zona pellucida, allowing cells trophectoderm establish contact with epithelium. Hatching begins continuous expansion blastocoel, thinning pellucida. The then exits through rupture, called zone. In humans, trophoblast close (ICM) – polar trophoectoderm rapidly proliferate differentiate follow endometrial invasion, being thus distinct from remaining trophoectoderm. association (according ICM localization) rates scarce. design, size, duration This prospective observational cohort study 588 patients underwent vitro fertilization (IVF) cycles autologous oocytes had fresh or frozen embryo transfer January/2018 August/2022 private ART center. All embryos were cultured time-lapse system (Embryoscope, Vitrolife) fertilized by ICSI IVF. Only reproductive outcomes (the presence/absence sac heartbeat) included this analysis. Participants/materials, setting, methods Embryos evidence natural (either penetration cells, regular disruption followed extrusion) included. Using as reference, blastocysts classified according position four categories: mass, intermediate (between opposite) multiple hatching. ANOVA, Fisher chi-squared tests applied properly for statistical p < 0,05 was considered significant. Main results role chance majority (n = 540, 77.4%), 88, 12.6%), 50, 7.2%) sites 20, 2.8%), total 698 analyzed. Maternal age similar groups (36,22±3,65; 36,03±3,3; 36,07±3,23; 37,35±3,57, 0.35, intermediate, respectively). 685, 98.1%), regardless mode insemination (IVF ICSI). Biopsied since they reached before biopsy. There no difference proportion euploid (64%) non-biopsied (36%) transfers subgroups (68% vs 32%; 64.3% 35.7%; 63.3% 36.4%; 50% respectively, 0.56). Positive rate group (47.7%, 0.04) when compared (59.3%). 54% 55% respectively. Clinical also (45.5%, (57%). 52% Limitations, reasons caution Two experienced senior embryologists position; however, operator subjectivity cannot be excluded. influence hole type (penetration disruption) debatable; nevertheless, both types all classification present IVF insemination. Wider implications findings potentially variable attention selection. proliferation differentiation may affect ability progress apposition, adhesion and, mostly importantly, invasion endometrium. Trial registration number Not applicable.