Embryo culture to the blastocyst stage does not select for gender

Abstract

Reports of increased developmental rates in male embryos have resulted in concerns that day 5 blastocyst transfer may lead to gender selection. We compared blastocyst development and prevalence of euploidy in XX vs. XY embryos. Retrospective analysis. We identified all women who underwent in vitro fertilization (IVF) with their first preimplantation genetic diagnosis (PGD) cycle for recurrent miscarriage, recurrent IVF failure, advanced maternal age, or other indications between January 1 and December 31, 2006. Fluorescence in situ hybridization was utilized to analyze 9 or 12 chromosomes. Embryos with abnormal sex chromosomes were excluded. P values were adjusted to account for lack of independence among embryos from the same woman. A total of 481 embryos from 99 cycles in 99 patients with complete results for the 9-chromosome panel were analyzed. 235 (49%) were XX and 246 (51%) were XY. The prevalence of euploidy was similar between the XX and XY embryos (30% vs. 32%, P=0.73). XX and XY embryos were equally likely to develop to the blastocyst stage by day 5 (59% vs. 60%, P=0.84), and those that became blastocysts had similar proportions of euploidy (41% vs. 37%, P=0.43). Results were similar in a subset of embryos in which all 12 chromosomes were analyzed. Abnormal numbers of individual autosomes were no more likely to occur in XX than XY embryos. XX and XY embryos are equally likely to develop to the blastocyst stage by day 5. Moreover, XX and XY blastocysts are equally likely to be euploid. There is no predilection for aneuploidy of any single autosome to occur with greater frequency in XX vs. XY embryos. Our data suggest that day 5 blastocyst culture does not result in gender selection and that euploidy and aneuploidy are not gender dependent.