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Introduction: Fetal diagnostics includes important analyses that provide information about the fetus. Various analyses are performed to determine or exclude genetic abnormalities in the fetus. Chromosome analysis for example is performed on fetal tissues such as amniotic fluid or chorionic villi sample (CVS). One issue with the current CVS chromosome analysis is that few metaphases are obtained that can be analyzed. Amniotic fluid, on the other hand, provides a greater metaphase range for analysis. Routines that differ between the CVS laboratory flow and the amniotic fluid laboratory flow are cell replating and subculturing.

Aim: The aim of the study was to examine whether the number of metaphases in CVS cultures can increase by performing cell replating on normal-grown cultures and to perform subculturing on overgrown cultures to improve the CVS laboratory flow. 

Materials and methods: Twelve samples were used, ten containing cells with normal chromosomes and two containing cells with trisomies. Classical cytogenetics approach was performed including cell culture, cell replating, subculturing, harvesting, preparation on slides and staining so metaphases could be counted. Mitotic index was then calculated.

Results and conclusion: Overall, the results showed that the number of metaphases increased in nine out of twelve samples when cell replating or subculturing was performed. However, no statistically significant difference for mitotic index was observed, due to limited number of samples. Nevertheless, the general trend speaks in favor of cell replating and subculturing. As such, these two processing steps will be implemented to the routine laboratory protocols.