Background: In human, as early as 7-8 days post fertilization, a small film of liquid gradually appears between the cells of epiblast layer that is called amniotic fluid. Broadly, the function of amniotic fluid fall into three main category; physical, functional and homeostasis. Since long time ago, this vital fluid has been the basis for the prenatal diagnosis (PND). The cells as a trivial fraction of amniotic fluid have the key role in PND approaches. The main drawback to cell culture-based methods is a phenomenon called chromosomal instability (CIN) in which loss and gain of some or whole chromosomes establishes aneuploidy and polyploidy in cultured cells, respectively. Objective: We investigate chromosomal instability in amniocytes obtained from pregnant women who were candidate for amniocentesis. Material and Method: Obtained amniotic fluid sample by amniocentesis were centrifuged at 400g for 15 min, then the cell pellet was comparatively cultured in supplemented Amniomax and DMEM, and incubated at 37 ͦ C under 5% humidified CO2. The samples were harvested between passage 4-6 when they were arrested and not be able to be passaged any more. Afterwards, the cells were harvested and fixed on slide for investigating possibility of aneuploidy and polyploidy by multi-color FISH probes for chromosomes 13,18,21, X and Y. Result and Conclusion: Our result showed any aneuploidy and polyploidy in cultured amniocytes by FISH, suggesting that chromosomal instability is very rare in cultured amniotic fluid cells. Only one of the samples showed Trisomy 21 which confirmed the results in the patient's case.

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