Day 3 embryo assessment does not provide a reliable prediction for blastocyst formation and designation: a retrospective cohort study

Although many Fertility Centers have adopted day 5 or 6 embryo transfer policy, yet, 30% of embryo transfers in the US are performed on day 3. This is mainly due to concerns related to longer embryo culture effect and higher rates of embryo transfer cancellation on day 5, with no effect on cumulative pregnancy rate. We conducted a retrospective cohort study comparing individual embryo transfer order rank, best embryo for fresh transfer and intention to freeze, of day-3 and day-5 embryos based on their morphology score. Day-3 embryos of each patient were ranked by embryologists for the order of transfer and intention to freeze, based on morphological score, blinded to actual blastulation outcome. The corresponding blastocysts were similarly ranked for the order of transfer and vitrification intention. Ranking was compared to test the predictive value of day-3 morphological assessment. Sixty patients with 784 day-3 embryos were included. There was only a moderate positive significant correlation between ranks on day-3 and ranks on day-5 [