Morphokinetic embryo behaviour in low-prognosis patients according to the POSEIDON criteria: an analysis of 3326 injected oocytes.

The objective of this cohort study was to investigate whether embryo quality and morphokinetic behaviour differ in the four groups of low-prognosis women as stratified by the POSEIDON criteria. The study was performed in a private university-affiliated in vitro fertilization (IVF) centre, and included 3326 injected oocytes from 846 women undergoing ICSI cycles between March 2019 and April 2022. Kinetic markers from the point of insemination were recorded in the EmbryoScope incubator. Generalized mixed models followed by Bonferroni post hoc were used to compare morphokinetics among the POSEIDON groups. Embryos derived from patients in the POSEIDON groups 2, 3 and 4 showed significantly slower divisions compared to those from POSEIDON 1 group. The KIDScore rank was significantly lower for embryos deriving from POSEIDON groups 2, 3 and 4 (2: 4.4 ± 0.7 vs. 3: 4.2 ± 0.2 vs. 4: 3.0 ± 0.4) compared to those deriving from POSEIDON 1 group (4.8 ± 0.1, p < 0.001). Group POSEIDON 1 showed improved implantation (26.9% vs. 2: 22.4% vs. 3: 20.0% vs. 4: 14.0, p < 0.001) and miscarriage rates (5.6% vs. 2: 31.2% vs. 4: 50.0%, p = 0.013). Embryo quality and morphokinetic behaviour differ across the POSEIDON groups, being more favourable in POSEIDON group 1, as well as implantation and miscarriage rates. Embryo development was more favourable in POSEIDON group 1 (young age and adequate ovarian reserve), suggesting that oocyte quality is determinant of embryo developmental potential. These findings show the reasonability of classifying POR by the POSEIDON criteria and provide information for counselling of POR regarding their possible prognosis.