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

PurposeTo 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.MethodsFrom 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.ResultsOocyte area decreased from t0 to tPNf after IVF and ICSI, and oocytes with larger area shrank faster (beta - 12.6 mu m(2)/h, 95%CI - 14.6; - 10.5, p < 0.001). Oocytes that resulted in a used embryo were larger at all time-points and reached tPNf faster than oocytes that fertilized but were discarded (oocyte area at tPNf in used 9864 +/- 595 mu m(2) versus discarded 9679 +/- 673 mu m(2), p < 0.001, tPNf in used 23.6 +/- 3.2 h versus discarded 25.6 +/- 5.9 h, p < 0.001). Larger oocytes had higher odds of being used (oocyte area at tPNf ORused 1.669, 95%CI 1.336; 2.085, p < 0.001), were associated with faster embryo development up to the morula stage (e.g., t9 beta - 0.131 min, 95%CI - 0.237; - 0.025, p = 0.016) and higher ICM quality.ConclusionOocyte area is an informative marker for the preimplantation development of the embryo, as a larger oocyte area is associated with higher quality, faster developing embryos, and higher chance of being used. Identifying determinants associated with oocyte and embryo viability and quality could contribute to improved preconception care and subsequently healthy pregnancies.

Automated summary

This study investigates the relationship between oocyte area and various factors related to embryo development, such as fertilization rate, embryo usage, and preimplantation embryo development. The results suggest that oocyte area can serve as a marker for optimal early embryo development.