Prenatal diagnosis: techniques used to help in ruling out maternal cell contamination

The combined findings from a number of different analytical techniques increases confidence that the cells analysed in amniotic fluid cell cultures are fetal in origin. Three hundred and twenty four fluids were processed using in situ processing of cultured amniotic fluid cells, allowing for analysis of mitoses from multiple colonies derived from multiple culture dishes. Screening of the same samples for fluorescent Y-chromatin was of help in indicating the genotypic sex of the primary cells. This was found to be accurate in 96% of the fluids checked. In cases where an XX complement is found, Q-polymorphism comparisons can be made between mitoses from the amniotic fluid cells and maternal lymphocytes. Of 29 such studies, 19 showed pronounced differences in their polymorphism constitution.