Human oocyte area is associated with preimplantation embryo usage and early embryo development: the Rotterdam Periconception Cohort

Purpose To investigate the association between oocyte area and fertilization rate, embryo usage, and preimplantation embryo development in order to establish if oocyte area can be a marker for optimal early embryo development. Methods From 2017 to 2020, 378 couples with an indication for IVF ( n = 124) or ICSI ( n = 254) were included preconceptionally in the Rotterdam Periconception Cohort. Resulting oocytes ( n = 2810) were fertilized and submitted to time-lapse embryo culture. Oocyte area was measured at the moment of fertilization (t0), pronuclear appearance (tPNa), and fading (tPNf). Fertilization rate, embryo usage and quality, and embryo morphokinetics from 2-cell stage to expanded blastocyst stage (t2-tEB) were used as outcome measures in association with oocyte area. Oocytes were termed “used” if they were fertilized and embryo development resulted in transfer or cryopreservation, and otherwise termed “discarded”. Analyses were adjusted for relevant confounders. Results Oocyte area decreased from t0 to tPNf after IVF and ICSI, and oocytes with larger area shrank faster (β − 12.6 µm 2 /h, 95%CI − 14.6; − 10.5, p