Routine amniocentesis is followed by a complex series of steps such as culturing, harvesting, staining, and reading of amniotic fluid for karyotype analysis of the fetal chromosome, which requires several weeks of waiting time. These weeks are an ordeal for both the pregnant woman and her family, especially as the gestational weeks gradually increase and fetal movements become more pronounced, the fear of being told after a few weeks that there is something wrong with the fetus and that labor needs to be induced is heightened, hence the clinical need for a rapid diagnosis. For some anxious, high-risk, and elderly pregnant women, a rapid diagnosis may be considered to know early if the fetus is normal. Some hospitals can use fluorescence in situ hybridization (FISH) to analyze fetal cells in amniotic fluid for the most common chromosomal abnormalities in the fetus, using DNA probes specific for chromosomes 13, 18, 21, X and Y. The results are usually available in 2-3 days and cover basically 95% of the common chromosomal abnormalities. If there are two chromosomal loci, the chromosome number is normal. If there are three chromosomal loci on chromosome 21, the fetus may have Down syndrome (see the left part of the figure below, with three red loci), which, combined with conventional karyotype analysis (see the right part of the figure below), can lead to an early conclusion.