Do male embryos grow faster than female embryos?

Abstract

Preimplantation genetic testing for aneuploidy (PGT-A) gives us insight into the chromosomal makeup of an embryo. It has been suggested that male embryos grow faster than female embryos and as a result embryologists are more likely to select a male embryo for transfer. The objective of this study is to assess whether an embryo’s sex and/or chromosomal normalcy may be related to their rate of development. A retrospective study of PGT-A results obtained between 2016 and 2018. Information was derived from PGT-A results of 151 patients (691 embryos; 21 uncounted due to being beyond parameters or missing information). We determined the ratios of day-5 XY to XX, labeling this as group A, day-6 XY to XX as group B, day-5 euploid (N) to aneuploid (AN) as group C, and day-6 N to AN as group D. These ratios were then tested to determine whether embryo growth exhibited any significant patterns. RESULTS: : A chi-square test for independence was performed on the ratios of four groups: A, B, C, and D. The former three groups’ ratios yielded no significant differences, with group B and C possessing ratios very close to an even split 50/50, which is consistent with the average prediction of embryo development. However, the latter group yielded a significant difference with 92:128 euploid to aneuploid ratio (p = 0.015).Tabled 1group Atotal Day 5 XY242Expected Value225total Day 5 XX208Expected Value225Chi-Squre TestP-Value:0.11Group BTotal Day 6 XY108Expected Value110Total Day 6 XX112Expected Value110Chi-Squre Testp-Value:0.79 Open table in a new tab Our results do not support the notion that male embryos grow faster than female embryos. The was a significant difference in the rate of aneuploidy seen when comparing day 6 blastocysts to those that reached the blastocyst stage on day 5.