O-148 Cumulative embryotoxic effect of IVF plastic devices used sequentially in routine clinical practice could slow the embryo development and delay blastulation
Authors: Delaroche L , Besnard L , Acacio M , Mestres E , Costa-Borges N 
Published: June 2023

Abstract

Study question
Is there an embryotoxic cumulative effect resulting from IVF plastic consumables (PC) when used sequentially under clinical routine practice?

Summary answer
Reduced blastulation rates and slow development were detected in some associations of PC evaluated by the Mouse Embryo Assay (MEA) suggesting possible cumulative embryotoxicity.

What is known already
Recommendations from European (ESHRE) and American (ASRM) societies regarding the use of IVF PC suggest that they should undergo appropriate quality control tests to detect the possible presence of embryotoxins. The main test used by manufacturers to exclude any embryotoxicity is the MEA. This assay is currently performed individually on each PC so that a certificate of conformity is delivered for each product/lot. However, several PC are used during a single IVF cycle, potentially creating an embryotoxic cumulative effect. To our knowledge, the cumulative toxicity of several PC used sequentially on gametes and embryos has not been studied so far.

Study design, size, duration
The objective of this prospective study was to determine if there is cumulative embryotoxicity when several PC are used together under clinical routine conditions. Ten associations, each containing 13 to 31 PC, were designed, and assessed for embryotoxicity using a MEA methodology. The tested combinations replicated the different steps used in an IVF cycle, including sperm collection and selection, oocyte pick-up, fertilization, embryo culture, embryo transfer, vitrification and thawing and sperm freezing.

Participants/materials, setting, methods
A defined volume of culture media was used to extract the toxicity of several PC used in every association in triplicate. The MEA tests were performed on each medium extraction with 21 one-cell stage fresh mouse embryos. Blastocyst formation rates after 96 and 120h of culture (Day 5/6), blastocyst good quality rates and hatched blastocyst rates were compared between the tested and control groups. The total cell number per blastocyst was also evaluated.

Main results and the role of chance
No toxicity was detected in the first two associations comprised of 22 and 23 PC, which mimicked the collection (either in sperm cups or in spermicide-free condoms) and processing of sperm samples.
However, the third association comprised of 32 plastic devices replicating the sperm collection in sperm cups, processing, and freezing in high security straws, showed toxicity as the mean blastulation rate at day 5 was reduced to 20.6% compared to 95.6% in the control group (p &lt; 0.05). Surprisingly, the mean blastulation rates observed at day 6 was 55.6% versus 100.0% in the control group (p &lt; 0.05). The blastocysts obtained at day 6 showed a mean number of cells (n = 112.5) significantly reduced in comparison with the control group (n = 167.9) (p &lt; 0.05), suggesting a sublethal presence of toxins which slowed embryo development down and delayed blastulation.
More experiments involving toxicity assessment in other associations of PC are currently undergoing and will be presented at the conference.

Limitations, reasons for caution
Sensitivity could vary depending on the methodologies used for toxicity extraction and MEA. The main cause, if any, of the detected toxicity will need to be pinpointed by analyzing each element of the affected associations individually.

Wider implications of the findings
Also, professionals should rationalize and minimize the number of plastic consumables used during the IVF procedures to reduce the potential accumulation of toxicity in the embryo culture system.

Trial registration number
Not applicable