Multiparameter analysis of previously frozen (A, C, E, and G) and nonfrozen (B, D, F, and H) low-density cells labeled with combinations of MoAbs. Maternal PB (A through D) and nongravida PB (E through H) were used to target two candidate populations of fetal cells: nucleated erythroid cells (NEC; CD71⁺ glycophorin A⁺ CD45^lo-int CD34⁻ PI⁻; A, B, E, and F ) and fetal CD34⁺ progenitor cells (CD34⁺ CD71⁻ glycophorin A⁻ CD45^int PI⁻; C, D, G, and H).