Disposition of chemicals in the developing embryo and fetus

The uptake of foreign compounds and their distribution in the embryo and fetus at different stages of gestation are reviewed. In particular studies performed by means of autoradiography are discussed. It is shown that a number of compounds may be almost completely blocked by the placental structures early in gestation, although they are foreign compounds. In late gestation often one or a few organs may accumulate a particular compound; this may be due to metabolism, affinity for tissue components, etc. In some cases the site of accumulation of tissue binding of a drug has correlated well with the teratogenic or carcinogenic effects.