First-trimester euploid miscarriages analysed by array-CGH

It is estimated that 10-15 % of all clinically recognised pregnancies results in a miscarriage, most of which occur during the first trimester. Large-scale chromosomal abnormalities have been found in up to 50 % of first-trimester spontaneous abortions and, for several decades, standard cytogenetic analysis has been used for their identification. Recent studies have proven that array comparative genomic hybridisation (array-CGH) is a useful tool for the detection of genome imbalances in miscarriages, showing a higher resolution, a significantly higher detection rate and overcoming problems of culture failures, maternal contamination and poor chromosome morphology. In this study, we investigated the possibility that submicroscopic chromosomal changes, not detectable by conventional cytogenetic analysis, exist in euploid miscarriages and could be causative for the spontaneous abortion. We analysed with array-CGH technology 40 foetal tissue samples derived by first-trimester miscarriages with a normal karyotype. A whole-genome microarray with a 100-Kb resolution was used for the analysis. Forty-five copy number variants (CNVs), ranging in size between 120 Kb and 4.3 Mb, were identified in 31 samples (24 gains and 21 losses). Ten samples (10/31, 32 %) have more than one CNV. Thirty-one CNVs (68 %) were defined as common CNVs and 14 were classified as unique. Six genes and five microRNAs contained within these CNVs will be discussed. This study shows that array-CGH is useful for detecting submicroscopic CNVs and identifying candidate genes which could account for euploid miscarriages.