Non-invasive prenatal diagnosis by isolation of both trophoblasts and fetal nucleated red blood cells from the peripheral blood of pregnant women

Objective To isolate fetal trophoblasts and nucleated red blood cells from the peripheral blood of pregnant women. Design Trophoblasts were isolated from whole blood of women in the first trimester of pregnancy by a specific monoclonal antibody, 340. Nucleated red blood cells were isolated by separating whole blood on a triple gradient, staining with ferromagnetic particles coated with an antitransferrin monoclonal antibody and separated on a mini magnetic activated cell sorting (MACS) column. Sorted cells were sexed using a nested polymerase chain reaction for a specific sequence on the Y chromosome and the sex was confirmed by karyotyping of chorionic villus samples. Participants Patients between 10 and 14 weeks of pregnancy who were undergoing elective chorionic villus sampling for the detection of fetal aneuploidies. Main outcome measure Fetal sex determined by polymerase chain reaction on fetal cells sorted from maternal blood. Results When both trophoblasts and nucleated red blood cells were sorted, fetal sex was correctly predicted in 12/13 cases (92%), which included correct diagnosis of five of six male pregnancies. More importantly the two techniques were complementary, with only one male pregnancy being diagnosed on both trophoblasts and nucleated red blood cells, two being detected only with trophoblasts and two on nucleated red blood cells alone. No false positives (male signal from a female pregnancy) were diagnosed with either trophoblasts or nucleated red blood cells even with the highly sensitive nested polymerase chain reaction technique, which is very prone to contamination. This study also shows that it is possible to isolate both trophoblasts and nucleated red blood cells from the same sample of maternal blood. Conclusion Fetal cells can be isolated from maternal blood at around 10 weeks of pregnancy.