P-033 Microfluific sperm sorting does not impact the primary sex ratio in IVF-ICSI treatments
Authors: Munuera Puigvert A , García-Faura Cirera A , García José F , Carella C , Pujal Bravo B , Montalvo Pallès V , Marquès López-Teijón B 
Published: July 2024

Abstract

Study question
Does sperm selection through microfluidics alter the primary sex ratio (PSR) when compared to density gradients?

Summary answer
The PSR is not modified when employing a microfluidic sperm sorting when comparing to the conventional density gradient technique for sperm selection.

What is known already
The PSR refers to gender after fertilization, this is often expressed as the male births per female births. Little is known about the sex ratio in natural and assisted reproduction treatments (ART) since it is difficult to establish in ART as it requires preimplantation genetic testing (PGT). Previous studies have been estimating the variation in the PSR based on the fertilization technique used or the day of embryo transfer. Even the influence of sperm selection techniques has not received much attention, using traditional sperm selection methods such as density gradients or swim-up, a PSR of 1.07 has been estimated.

Study design, size, duration
This is a retrospective study that includes 1764 blastocysts stage embryos biopsied from 522 autologous preimplantation genetic testing for aneuploidies cycles (PGT-A) performed between January of 2020 and December of 2022 and analysed through Next Generation Sequencing (NGS). All the embryos were cultured under the same conditions with one-step media in a time-lapse incubator and the PGT-A was performed in day 5 or day 6 of culture to determine the embryo ploidy status.

Participants/materials, setting, methods
Two groups were established based on the sperm selection method before ICSI. The study group using a microfluidic system (MS; ZyMōtICSI® or ZyMōtMulti®) included 256 blastocysts from 98 cycles, and a control group using density gradients (DG), with 1058 blastocysts from 424 cycles were compared. PGT-A determined the embryonic sex and for the PSR estimation, number abnormalities in the sexual chromosomes were excluded (i.e. XXY, X0, XYY). Chi-square test was performed to compare the groups.

Main results and the role of chance
Our data show that there was no statistical significance in the overall ratio of XY:XX embryos biopsied between both groups (p = 0.09). The PSR was 0.89 (47:53) in the study group (MS) and 1.12 (53:47) in the control group (DG). Although not statistically significant, the rate of XX embryos was 6% higher than XY embryos in the MS group. In contrast, in the DG group, the same increase in the rate of XY embryos was observed. If we consider only the euploid embryos which are the potentially born babies, the PSR acquires values of 0.96 for the DG group and 0.92 for the MS group (p = 0.86), showing an increase in euploid female embryos transferred compared to those euploid male embryos. However, it was not statistically significant.

Limitations, reasons for caution
The performance of PGT-A on blastocysts does not provide an entirely accurate representation of the PSR since it is carried out 5/6 days after the moment of fertilization; nevertheless, it is the technique that comes closest. Also, the low number of blastocysts in the study group represents a limitation.

Wider implications of the findings
The sperm selection for ICSI with microfluidic technology does not significantly alter the PSR.

Trial registration number
Not applicable