Non-invasive molecular analysis of fetal DNA is the diagnostic goal of prenatal medicine. Circulating fetal DNA can be detected in maternal plasma. Recently, it has been detected in the urine of pregnant women. We hypothesize that fetal DNA is present also in maternal saliva and that advances in stabilization and isolation of nucleic acids from saliva enable non-invasive and repeated sampling for prenatal diagnostics. The hypothesis is testable using saliva samples of pregnant women with confirmed male fetuses. Y-specific sequences should be detectable in salivary DNA. Caution must be given to the prevention of contamination. If proved in large studies, the presence of fetal DNA fragments in maternal saliva would enable a wide range of applications in prenatal medicine.