Impact of parental gonosomal mosaicism detected in peripheral blood on preimplantation embryos

Abstract

This study evaluated the chromosomal condition of embryos generated by patients with an altered karyotype due to gonosomal mosaicism and the clinical outcome after preimplantation genetic diagnosis (PGD) for aneuploidy. Thirty-six patients aged 34.6 ± 3.6 years performed 54 treatment cycles and had 295 embryos diagnosed by fluorescence in-situ hybridization (FISH). Thirty-seven per cent of the embryos were chromosomally normal and generated 19 clinical pregnancies after replacement in 39 cycles. Only one pregnancy miscarried, yielding a take-home baby rate of 33.3%. Autosomal monosomy and trisomy contributed 36.1% of total abnormalities and gonosomal aneuploidy 5.9%, similar to the results detected in patients who undergo PGD for increased maternal age. Reanalysis was performed on 114 non-transferrable embryos: 41 were found to be mosaics, which were grouped in three different types, chaotic mosaics (56%), aneuploid mosaics (29%) and diploid/haploid/polyploid mosaics (15%). The incidence of aneuploid mosaics was higher than expected compared with PGD patients of the same age and resembled the condition observed in patients of advanced maternal age. These findings suggest that constitutional carriers of sex chromosome mosaicism are predisposed to autosomal mosaicism of embryos, possibly due to errors of cell division. There is an indication that this tendency is higher in female than male carriers.