Last update:
25-Nov-2018

OBJECTIVE To determine the incidence of X chromosome mosaicism in infertile women to be enrolled in an in vitro fertilization cycle (IVF).

METHOD The study sample consisted of 254 women (average age: 41.1 years) who were planning to undergo an IVF. Karyotyping was performed on their peripheral blood lymphocytes by conventional cytogenetics techniques. For each woman, 25 G-banded metaphases were studied, while in the case of suspected mosaicism, the analysis was extended to 100 metaphases. Mosaicism of <3% was not reported.

RESULTS Of the study women, 78.3% had a normal karyotype (46,XX), while 21.7% had various chromosomal abnormalities. Three women (1.2%) carried autosomal chromosome abnormalities and 52 (20.5%) had sex chromosome X aneuploidies in a mosaic form. Specifically, 34 (65.5%) showed low level mosaicism (3–6%), while in 18 women (34.5%) X chromosome mosaicism of >6% was detected. The incidence of mosaicism was statistically significantly higher in the women aged >35 years, compared to the younger women, a finding consistent with loss of chromosome X with ageing. The number of aneuploid cell lines was observed to be increased in the older women. Women aged >45 years more frequently had 3 or 4 cell lines, compared with the younger women (<35 years) who had a mosaic of two cell lines (45,X/46,XX).

CONCLUSIONS The most commonly observed chromosomal abnormality in infertile women is X chromosome mosaicism. X chromosome aneuploidies and the presence of two or more abnormal cell lines appear to be related to an increase in age. In couples referred for assisted reproduction, it is therefore important to take into account the cytogenetic findings in order to select the most appropriate protocol.

Key words: Chromosomal abnormalities, Mosaicism, Sex chromosomes.