A high incidence of maternal cell contamination of amniotic fluid cell cultures

Maternal cell contamination (MCC) of amniotic fluid cell cultures was detected as an admixture of male and female cells in 15 out of 3,000 cases. Allowing for undetected cases (in which the fetal karyotype is female), the true incidence of MCC may be as high as 1%. Cultures affected by MCC were, in general, established from fluid samples without obvious blood contamination. No common obstetrical or amniocentesis procedural factors could be recognized among those cases affected by MCC. The proportion of maternal cells was highly variable and in some instances maternal cells were present in multiple cultures. In this series, MCC has not led to any cytogenetic misdiagnoses. MCC may pose its greatest danger for prenatal biochemical diagnoses where the properties of an entire cell population are determined.