P-252 Oolemma surface area impacts human pre-implantation embryo development and usage: The Rotterdam Periconception Cohort

Abstract Study question Does oolemma area change before the 2-cell stage? Is oolemma area associated with fertilization rate, embryo usage rate and preimplantation embryo development? Summary answer Oolemma area is associated with preimplantation embryo development, the odds of fertilizing and developing into a used or discarded embryo. What is known already Current morphological grading systems are based on embryo morphology and omit oocyte morphology. Fertilization and embryo potential are largely determined by the maturation and quality of the oocyte. Oocyte quality correlates to morphology, and the very early stages of embryo development are critical to changes in oocyte size. Larger oocyte size associates with higher quality blastocyst. This suggests that oocyte size can be a morphological marker of preimplantation embryo quality and assisted reproductive treatment (ART) outcomes. Study design, size, duration This study is embedded in the Rotterdam Periconceptional Cohort, an ongoing prospective tertiary hospital-based birth cohort study. From May 2017 to July 2020, a subcohort of 378 women that underwent ART was included comprising of 124 pregnancies after in vitro fertilization (IVF) and 254 after intracytoplasmic sperm injection (ICSI). Participants/materials, setting, methods Health, lifestyle and treatment factors were collected from detailed self-reported questionnaires and medical records. Oolemma area was measured at the time of fertilization (t0), pronuclear appearance (tPNa) and fading (tPNf). Oolemma area trajectories (slope surface t0-tPNf) were calculated with linear regression. Fertilization rate, embryo usage rate, and embryo morphokinetics were analyzed in association with oolemma area and trajectories. Analyses were performed with linear mixed models, mixed effects logistic regression, and adjusted for relevant confounders. Main results and the role of chance Oolemma area decreased from t0 to tPNf for oocytes that developed into both used or discarded embryos. Oolemma area at t0 was strongly associated with the rate of area shrinking, as larger oolemma areas had faster shrinking rates (Bshrinking -12.55 µm²/hour, 95%CI -14.55; -10.55, p