Aneuploidy screening in coelomic samples using fluorescence in situ hybridisation (FISH)

Coelocentesis is the earliest invasive prenatal diagnostic procedure that has recently been used in ongoing pregnancies to identify single gene defects. Aneuploidy screening has not yet been performed in ongoing pregnancies following coelocentesis, but experimental studies have demonstrated the ability of determining the copy number of chromosomes 13, 18, 21, X and Y in uncultured coelomic samples, by FISH or PCR. The aim of this study was to extend previous studies and investigate the feasibility of analysing uncultured coelomic fluid samples for 11 chromosomes using fluorescence in situ hybridisation (FISH).

Coelocentesis was performed in 12 singleton pregnancies at 6 to 9 weeks of gestation immediately before surgical termination of pregnancy. Fluorescence probes for chromosomes 3,7,9,13,16,17,18,21,22, X and Y were applied on uncultured coelomic-fluid samples and placental tissue. In cases where coelomic cells were not of a sufficient amount, chromosomes X and Y were analysed in a second layer of hybridisation.

Successful analysis by FISH was possible in all cases and the results from the coelomic fluid were concordant with those from the analysis of placental tissue and obtained within a few hours of receiving the samples. Problems associated with limited cell numbers were overcome by the application of a second layer of FISH. This sequential approach has also enabled accurate identification of maternal-cell contamination in male samples.

Analysis of 11 chromosomes using FISH in coelomic fluid samples is feasible and it has the potential to be applied for rapid aneuploidy screening, should coelocentesis be used clinically as an early, invasive prenatal diagnostic tool.