Detection of fetal nucleated red blood cells (NRBCs) is achieved by employing a combination of brightfield and fluorescence images of nuclear and cytoplasmic markers. The brightfield and fluorescence images are all obtained with a single multibandpass dichroic mirror. The objects in the sample are stained with a fluorescent dye that selectively stains nuclei and a dye that selectively stains fetal hemoglobin in the cytoplasm of fetal RBCs. UV excitation provides fluorescent emissions from the stained cell nuclei and visible illumination provides brightfield transmission of light that is absorbed by the stained cytoplasm. The images are processed to determine regions where the fluorescent emissions by cell nuclei in response to the UV excitation and the absorption by fetal hemoglobin of the brightfield illumination overlap or are in close proximity. The brightfield and fluorescence images may be sequentially acquired or derived from a single image where the UV excitation and visible illumination occur simultaneously.