Objective
To use trophoblast cells accumulating in the endocervical canal at the beginning of pregnancy for noninvasive prenatal testing. Design: Prospective, double-blinded test for fetal gender. Setting: Academic medical center. Patient(s): Fifty-six women with singleton pregnancies at gestational age 5-20 weeks. Intervention(s): Isolation of fetal cells from resident maternal cells in endocervical specimens using anti-human leukocyte antigen G coupled to magnetic nanoparticles; cell phenotyping immunofluorescently with a panel of trophoblast subtype-specific proteins; DNA integrity assessment with terminal dUTP nick-end labeling (TUNEL); and polymerase chain reaction (PCR) and fluorescent in situ hybridization (FISH) to detect sex chromosomes in individual cells. Main outcome measure(s): Trophoblast phenotype, TUNEL index, and percentage male cells. Result(s): The women were given a routine Papanicolaou test; fetal genders were verified from medical records. Recovery after immunomagnetic isolation averaged 746±59 cells across gestational age, with 99% expressing chorionic gonadotropin, whereas the depleted cell fraction expressed none. The isolated cells had an extravillous trophoblast phenotype and intact nuclear DNA (>95%). Fetal gender was determined in 20 specimens without error by PCR. The FISH analysis of isolated cells from male specimens validated their fetal origin.