Chromosome polymorphisms in karyotypes from amniotic fluid cell cultures.

Frequencies of 12 fluorescent chromosome polymorphisms were scored from Q-banded karyotypes derived from 108 midtrimester diagnostic amniotic fluid cell cultures. The most frequent variants were the bright fluorescent short arm of chromosome 13 (P = 0.458) and the bright fluorescent marker close to the centromere on chromosome 3 (P = 0.426).The polymorphism pattern was found to be different between the maternal (blood culture) and fetal (amniotic fluid cell culture) karyotypes in each of the 25 paired cases studied. This technique is valuable in prenatal diagnosis to exclude possible maternal cell contamination and outgrowth in cases where the amniotic fluid cell cultures reveal a female karyotype.