Placental structure, function and drug transfer

In the late 1950s and early 1960s, the devastating series of thalidomide-induced birth defects raised awareness of the imperfect state of the placenta as a barrier to drug transfer. Subsequent research has sought to elucidate the precise nature and mechanisms of transplacental drug passage. There has also been increasing interest in the deliberate use of maternally administered drugs designed to cross the placenta and provide therapeutic effects on the fetus. This article reviews the structure and key functions of the placenta. It also summarizes our current understanding of placental drug transfer, particularly of drugs used for anaesthesia and analgesia in pregnancy.