Abstract
The presence of contaminating maternal cells in amniotic fluid is an important, though infrequent, cause of error in karyotyping the fetus. A method of detecting contaminating maternal cells in amniocentesis specimens by determining the HLA phenotype of the cells of amniotic fluid and the mother is described. Tissue typing of 15 amniocentesis specimens was performed, and in 14 cases the fetal origin of the cells was established. In one case, the results of tissue typing suggested maternal cell contamination, though this had not been suspected from chromosome studies of the amniotic fluid cell cultures. Other possible uses for tissue typing of amniotic fluid specimens for prenatal diagnosis are also described.