P-304 Does imaging affect embryo health? Comparative analysis of discrete wavelengths of light on the developing embryo
Authors: Dunning K , Campugan C , Lim M , Chow D , Tan T , Li T , Saini A , Orth A , Reineck P , Schartner E , Thompson J , Dholakia K 
Published: June 2023

Abstract

Study question
What is the effect of exposing the embryo to discrete wavelengths of light on preimplantation development and resultant offspring health?

Summary answer
Exposure of embryos to red or yellow wavelengths negatively impacted embryo health, pregnancy rate and resulted in offspring that were heavier at weaning.

What is known already
Previous studies have indicated a potential negative impact of shorter wavelengths of light on embryo health. Red and yellow wavelengths are widely considered benign and utilised clinically in time-lapse equipped incubators within IVF clinics. However previous studies had not uniformly and correctly irradiated embryos to enable a fair comparison between different wavelengths.

Study design, size, duration
A current aim of the field is to use optical imaging to predict embryo developmental potential. Such approaches use varying wavelengths of light. The impact of irradiating the embryo with discrete wavelengths of light is not fully understood. Here, we assess the impact of various wavelengths on the developing embryo and for the first time, ensured that the energy dose applied was consistent between wavelengths, thus mimicking fluorescence and time-lapse imaging (470 – 620 nm).

Participants/materials, setting, methods
Preimplantation mouse embryos were exposed daily to blue (470 nm), green (520 nm), yellow (590 nm) or red (620 nm) wavelengths and compared to embryos that were not exposed. We assessed embryo development, DNA damage, and postnatal outcomes following transfer to pseudopregnant recipients.

Main results and the role of chance
We found exposure to the yellow wavelength significantly impaired embryo development to the blastocyst stage (P &lt; 0.05). While exposure to blue, green and red wavelengths resulted in significantly higher levels of DNA damage when compared to unexposed embryos (P &lt; 0.05). The pregnancy rate was significantly lower when embryos were exposed to the red wavelength (P &lt; 0.05). Interestingly, resultant offspring were significantly heavier when derived from red or yellow light exposed embryos compared to those derived from unexposed embryos (P &lt; 0.01). Towards understanding the effect on offspring weight we assessed intracellular lipid abundance in the embryo. We found lipid abundance to be significantly elevated following exposure to yellow wavelength (1.8-fold, P &lt; 0.0001) but not red. We believe that the role of chance is low as results were collected from multiple independent experimental replicates that were tested using appropriate statistical analyses.

Limitations, reasons for caution
While we demonstrate the distinct impacts of discrete wavelengths of light on the developing mouse embryos including post-natal effects, confirmation of these results in human embryos is required.

Wider implications of the findings
Red and yellow wavelengths are utilised clinically in time-lapse equipped incubators within IVF clinics. Our results demonstrate the potential need to re-evaluate these assumptions. Mapping the stress tolerance embryos show for each wavelength may be advantageous in identifying how damage can be mitigated in clinical manipulation and imaging techniques.

Trial registration number
not applicable