P-254 Short-time or overnight co-incubation with sperm in conventional IVF delivers similar pre-implantation development outcomes: a sibling cumulus-oocyte complex study
Authors: Bayram A , Elkhatib I , Abdala A , De Munck N , Kalafat E , Melado L , Lawrenz B , Nogueira D , Fatemi H 
Published: June 2023

Abstract

Study question
Does a short-time co-incubation in conventional IVF improve rates of fertilization, embryo development and euploidy, when compared to overnight co-incubation?

Summary answer
There is no significant difference in fertilization, embryo development and euploidy rates between sibling oocytes subjected to short co-incubation versus overnight co-incubation.

What is known already
Conventional IVF usually implies coincubation of cumulus-oocyte complex(es) with sperm for an overnight period. This overnight incubation might create an over exposure of COCs to reactive oxygen species (ROS), which might disturb oocyte homeostasis, and impact on embryonic developmental rate. To this extend, many early studies have compared a short co-incubation time (2-6 hours) with overnight co-incubation, with reported conflicting outcomes. None of the studies combined time-lapse monitoring with short co-incubation, which allows the identification of early morphokinetic events of the inseminated oocytes after conventional IVF, as already known for ICSI oocytes in time-lapse incubators.

Study design, size, duration
This single center prospective study included 604 COCs in 38 IVF/ICSI cycles with preimplantation genetic testing between December 2020 and November 2022. After oocyte retrieval a min of 6 COCs were assigned for insemination by IVF and equally divided between short(2hrs) and overnight (16-20hrs) co-incubation. Supernumerary oocytes were denuded and inseminated by ICSI. Primary endpoint was fertilization rate; secondary endpoints were maturation rate, ploidy rate after trophectoderm biopsy, embryo development and morphokinetics.

Participants/materials, setting, methods
Couples with a female age between 18-43 (average:34.4) years, BMI ≤30kg/m2 and normal semen parameters (WHO) in the fresh ejaculate on the day of OR, were eligible for the study. After IVF, all embryos were cultured in a time-lapse imaging system in Global Total LP media. Blastocysts (≥Bl3BCC) were subjected to trophectoderm biopsy on day 5-7 and next generation sequencing (NGS) to determine blastocyst ploidy status.

Main results and the role of chance
In total, 288 oocytes (47.7%) were denuded for ICSI, whereas 316 (52.3%) oocytes were randomized 1:1 to short and overnight co-incubation groups. Maturation rates (M2/COC) and normal fertilization rates (2PN/COC) in short and overnight co-incubation groups were similar (88.0% vs 83.5%, P = 0.074 and 60.8% vs 62.0%, P = 0.193, respectively). Day-3 embryo cell numbers (P = 0.383), fragmentation rates (P = 0.529), blastulation rates on day 5 (39.9 vs 38.0% P = 0.696), time to blastulation (median: 112.6 vs 111.1 hours after insemination by time lapse, P = 0.544) were similar between short and overnight co-incubation groups. In total, 48 embryos in short and 45 embryos in overnight co-incubation groups were of sufficient quality for biopsy resulting in similar euploidy rates between the groups (39.6 vs 44.4%, P = 0.791).
When compared to their siblings in ICSI, short (mean difference: -6.48%, 95% CI: -18.5 to 5.59%, P = 0.290) and overnight co-incubation (mean difference: -0.87%, 95% CI: -12.9 to 11.2%, P = 0.886) attained similar fertilization rates per cycle. No significant differences regarding blastulation and euploidy rates were observed in short or overnight co-incubation compared to ICSI in unadjusted and adjusted analyses.

Limitations, reasons for caution
This is a prospective study with a limited patient population with a normal ovarian response. Results might not be transferable to patients with high or low ovarian reserve.

Wider implications of the findings
The present study demonstrated that there is no difference between short and overnight co-incubation in terms of fertilization and euploidy rates. Therefore short co-incubation might allow us to benefit from early denudation, and to investigate early morphokinetics in time lapse monitoring, which are otherwise missed by overnight co-incubation.

Trial registration number
NCT04627545