Non-invasive exclusion of fetal aneuploidy in an at-risk couple with a balanced translocation

A pregnant woman who was a carrier for a balanced chromosome translocation [46,XX, t(1;6) (p31;q14)] and who had had six miscarriages, declined invasi ve testing but agreed to non-invasive prenatal diagnosis by analysis of fet al cells in maternal blood. Monoclonal antibody (Mab) against the zeta (z) and gamma (gamma) chains of embryonic and fetal haemoglobin were used to id entify fetal nucleated erythrocytes (FNRBC). There were no FNRBC detected a t 7 weeks, one anti-z-positive FNRBC was detected at 11 weeks, and 12 anti- gamma-positive FNRBC were detected at 20 weeks. Fluorescent in-situ hybridi zation was performed using probes for chromosomes X, Y, 1 and 6 to identify feta I gender and the presence of an unbalanced chromosomal translocation. A tentative prenatal diagnosis was made of a female fetus disomic far chro mosomes 1 and 6. A female infant with a 46,XX karyotype was born at term. T his is the first attempt of exclusion of a chromosome translocation using f etal cells isolated from maternal blood. There is an advantage of using fet al cells isolated from maternal blood for non-invasive prenatal diagnosis i n couples who have a history of multiple miscarriages due to a parental tra nslocation, and who decline invasive testing in a pregnancy that continues to the second trimester.