Aneuploidy 16 in human embryos increases significantly with maternal age

Abstract

Objective: To determine aneuploidy for chromosome 16 by recycling nuclei of cells already analyzed for chromosomes X, Y, 18, 13, and 21 using multiple fluorescence in situ hybridization in preimplantation human embryos in a time frame compatible with clinical IVF and to asssess the incidence of chromosome 16 aneuploidy in embryos related to maternal age.

Design: Prospective experimental study.

Setting: In vitro fertilization program in a tertiary center.

Patients: One hundred four consenting patients undergoing IVF.

Main outcome measures: Chromosome 16 ploidy was analyzed in a total of 195 embryos. In 89 embryos, a standard multiple-probe fluorescence in situ hybridization was used for chromosomes X, Y, 18 and 16 (series 1). The remaining 106 embryos (series 2) were reanalyzed with a new procedure for chromosome 16, which involves rehybridization with a digoxigenin-labeled alpha satellite probe after the standard analysis for chromosomes X, Y, 18, 13, and 21 was completed. The embryos were assigned to one of three groups according to the women's age; group 1: </= 34 years (n = 34), group 2: 35 to 39 years (n = 47); group 3: >/= 40 years (n = 23).

Results: Successful analysis, including biopsy, fixation, and fluorescence in situ hybridization was achieved in 86% of the blastomeres within approximately 10 hours. A significant relationship was found between the rate of aneuploidy for chromosome 16 and increasing maternal age: group 1: 0%, group 2: 6.3%, and group 3: 11.7%. Monosomy for chromosome 16 was found in 72.7% of the 11 embryos carrying chromosome 16 anomalies, with the remaining three embryos having two trisomies and one tetrasomy. This new protocol was applied clinically to five patients undergoing preimplantation aneuploidy assessment. Aneuploidy for chromosome 16 was found in five embryos from three of those patients.

Conclusions: This study demonstrates that preimplantation genetic diagnosis of the major human aneuploidies is achievable within a time frame compatible with IVF. In addition, this study confirms, for embryos, the existing data from spontaneous abortions suggesting that chromosome 16 aneuploidy increases with maternal age. The high prevalence of embryonic monosomy, which is rarely found in spontaneous abortions, suggests that monosomy 16 could be a factor associated with failure of implantation, as well as pointing to a different mechanism involved in the generation of chromosome 16 aneuploidy.