Genetic diagnosis and therapy is well established in the antenatal period. The advancement of uterine and in vitro fertilization allow access to the early blastocyst. Simultaneously, laboratory techniques are being miniaturized to be sufficiently sensitive and specific for diagnosis with only a few cells. Thus genetic diagnosis and therapy may be extended from the antenatal patient to the antegravid patient. This article discusses the techniques of uterine lavage and in vitro fertilization as well as the diagnostic possibilities that this early embryonic period offers.