Embryo quality, ploidy, and transfer outcomes in male versus female blastocysts

The goal is to determine if variations exist between male and female blastocysts in preimplantation measurements of quality and ploidy and in vitro fertilization elective single-embryo transfer (eSET) outcomes.

A retrospective chart review was conducted from a private fertility center's database of blastocysts undergoing preimplantation genetic testing for aneuploidy, along with details of eSET from this screened cohort. Main outcomes included preimplantation embryo quality and sex-specific eSET outcomes.

A total of 3708 embryos from 578 women were evaluated, with 45.9% male and 54.1% female. The majority were High grade. No difference existed between embryo sex and overall morphological grade, inner cell mass or trophectoderm grade, or blastocyst transformation day. Female blastocysts had a higher aneuploidy rate than male blastocysts (P < 0.001). Five hundred thirty-nine eSETs from 392 women were evaluated, with High grade embryos more likely to have implantation (P < 0.001), clinical pregnancy (P < 0.001), and ongoing pregnancy (P = 0.018) than Mid or Low grade embryos. Day 5 blastocysts were more likely to have implantation (P = 0.018), clinical pregnancy (P = 0.005), and ongoing pregnancy (P = 0.018) than day 6 blastocysts. Male and female embryos had similar transfer outcomes, although female day 5 blastocysts were more likely to result in clinical pregnancy (P = 0.012), but not ongoing pregnancy, than female day 6 blastocysts. Male eSET outcomes did not differ by blastocyst transformation day.

Male and female embryos have comparable grade and quality; however, female embryos were more likely to be aneuploid. Ongoing pregnancy rates did not differ by embryo sex. Day 5 embryos had more favorable transfer outcomes than day 6 embryos.