Delays in the final stages of fertilization are strongly associated with trichotomous cytokinesis and cleavage arrest.

Purpose: Recent evidence showed that the phase between pronuclear fading and the first cleavage is a perilous bridge connecting the zygote and the embryo. Indeed, delay in the short interval between pronuclear breakdown (PNBD) and the first cytokinesis may result in chromosome segregation errors. We tested the hypothesis that delays in this final phase of fertilization are associated with a detrimental impact on embryo development.

Time will tell: time-lapse technology and artificial intelligence to set time cut-offs indicating embryo incompetence.

Study Question: Can more reliable time cut-offs of embryo developmental incompetence be generated by combining time-lapse technology (TLT), artificial intelligence, and preimplantation genetics screening for aneuploidy (PGT-A)?

Summary Answer: Embryo developmental incompetence can be better predicted by time cut-offs at multiple developmental stages and for different ranges of maternal age.

What Is Known Already: TLT is instrumental for the continual and undisturbed observation of embryo development. It has produced morphokinetic algorithms aimed at selecting embryos able to generate a viable pregnancy, however, such efforts have had limited success.

Changes in DNA repair compartments and cohesin loss promote DNA damage accumulation in aged oocytes.

Oocyte loss, a natural process that accelerates as women approach their mid-30s, poses a significant challenge to female reproduction. Recent studies have identified DNA damage as a primary contributor to oocyte loss, but the mechanisms underlying DNA damage accumulation remain unclear. Here, we show that aged oocytes have a lower DNA repair capacity and reduced mobility of DNA damage sites compared to young oocytes.