P-216 Evaluation of embryo quality and morphokinetics following short exposure of oocytes to spermatozoa
Authors: Koifman M , Blais I , Oron G , Baratz-Lahav S 
Published: June 2023

Abstract

Study question
Does embryo quality and morphokinetics following short exposure of oocytes to spermatozoa differ from conventional long exposure?

Summary answer
No statistical differences were found in embryo quality and morphokinetics following short exposure. Short exposure technique enables better monitoring of the embryos and easier handling.

What is known already
Overnight exposure of oocytes to spermatozoa may lead to toxic effects associated with reactive oxygen species. In short exposure, the duration of oocyte incubation with the sperm is reduced to 2-4 hours. Few studies showed that embryo morphology as well as pregnancy rates improved by short exposure, however, this remains controversial. Embryo morphokinetics in a time-lapse incubator yielding more accurate information on embryo quality, has not been reported for embryos derived by the short exposure technique.

Study design, size, duration
A retrospective study (2013-2019) 536 IVF cycles were included: 110 short exposure and 426 conventional IVF (long exposure). All embryos were cultured in the EmbryoScope. Short and long exposure cycles were compared for the average embryo scores of general and adapted laboratory in-house models. Groups were analyzed according to 2, 3 and 5 days of culture and maternal age. Moreover, differences of KID (Known implanted data) embryos morphokinetics were compared for cell division timings.

Participants/materials, setting, methods
IVF patients with mechanical factor, normal sperm counts. In conventional IVF, the oocytes were inseminated 6-7 hours post retrieval and mechanically denuded after 18-20 hours of incubation. In short exposure, the oocytes were inseminated and denuded 2-3 hours post retrieval and immediately placed in the EmbryoScope, for accurate annotation. In both methods oocytes were washed, incubated in EmbryoScope and cultured till the day of transfer. Women were divided by age groups: &lt;35, 35-40 and &gt;40.

Main results and the role of chance
No statistical difference was found in embryo cleavage rates and number of transferred embryos per cycle between long and short exposure in all three maternal age groups. The clinical pregnancy rate was slightly higher in the short exposure compared to the long exposure group but did not reach statistical significance (37.5% vs 32.5, p = NS). In women younger than 35y, elective single embryo transfer resulted in a statistically significant higher clinical pregnancy rate in the short exposure group compared to the long (p = 0.037). No significant differences were found in the average embryo morphokinetic score according to the general model and the adapted in-house model between the two groups. Moreover, no difference was found in embryo morphokinetics between short and long exposure in 272 KID negative and 116 KID positive embryos.

Limitations, reasons for caution
Since the study was retrospective and the short exposure group was smaller than the conventional IVF group, additional studies are needed to support our results.

Wider implications of the findings
Short exposure is more convenient and easier to perform. It is as good as long exposure in terms of clinical pregnancy rates and may be beneficial in patients younger than 35 years old.

Trial registration number
0015-20-CMC