The impact of severe oligozoospermia on morphokinetic embryo development in low-prognosis patients according to the Patient-Oriented Strategies Encompassing IndividualizeD Oocyte Number criteria: an analysis of 10,366 injected oocytes

Objective: To study whether severe male factor infertility (SMF), reflected by oligozoospermia, impacts embryo morphokinetic behavior in low-prognosis women as stratified by the Patient-Oriented Strategies Encompassing IndividualizeD Oocyte Number (POSEIDON) criteria.

Design: Cohort study.

Setting: Private university-affiliated in vitro fertilization center.

Patient(s): A total of 10,366 injected oocytes from 2,272 women who underwent intracytoplasmic sperm injection cycles between March 2019 and April 2022.

Intervention(s): Patients were divided into 8 groups according to the POSEIDON criteria (1-4) and the presence or absence of SMF. A control group of normoresponder patients was included. Kinetic markers from the point of insemination were recorded in the EmbryoScope incubator.

Main outcome measure(s): Morphokinetic milestones and intracytoplasmic sperm injection clinical outcomes.

Result(s): Embryos from patients in the POSEIDON 1 group showed significantly slower timing to pronuclear appearance, timing to pronuclear fading (tPNf), timing to 2 (t2), 3 (t3), 4 (t4), 6 (t6), and 7 (t7) cells than those from the control group. Known Implantation Diagnosis Score ranking was significantly different between the SMF and non-SMF (nSMF) subgroups in both POSEIDON 1 as well as control groups. Embryos from patients in the POSEIDON 2 group showed significantly slower timing to pronuclear appearance, t4, t6, t7, timing to 8 cells (t8), and timing to morulae than those from the control group. Embryos in the POSEIDON 2 SMF subgroup took longer than those in the POSEIDON 2 nSMF subgroup and those in both control subgroups to achieve tPNf, t2, t3, timing to 5 cells (t5), timing to start blastulation, and timing to blastulation. Known Implantation Diagnosis Score ranking was significantly different between the SMF and nSMF subgroups in both POSEIDON 2 as well as control groups. Embryos from patients in the POSEIDON 3 group showed significantly slower t8 and duration of the second cell cycle (t3-t2) than those from the control group. Known Implantation Diagnosis Score ranking was significantly different across the subgroups. Embryos derived from patients in the POSEIDON 4 group showed significantly slower tPNf, t2, t3, t4, t5, t6, t7, t8, timing to complete t4-t3 synchronous divisions, and timing to complete t8-t5 synchronous divisions than those from the control group. Known Implantation Diagnosis Score ranking was significantly different between the SMF and nSMF subgroups in both POSEIDON 4 as well as control groups. Irrespective of sperm quality, clinical outcomes significantly improved in the control subgroups compared with those in the POSEIDON 2 and 4 subgroups.

Conclusion(s): Embryos in the SMF groups presented lower Known Implantation Diagnosis Score ranking than those in the nSMF groups in both POSEIDON 1-4 and control groups, suggesting that cumulative differences result in worse morphokinetic development when the algorithm is used.