Drug therapy of the fetus.

The fetus has become an intended object of drug therapy administered through the mother with the successful prevention of hyaline membrane disease with glucocorticoids. Maternal drug treatment has now been undertaken for a variety of fetal problems, including arrhythmias, congestive heart failure, infections, and inborn errors of adrenal metabolism. Interestingly, this planned maternal drug exposure during pregnancy coincided with increasing concerns during the last two decades about inadvertent transplacental exposure of the fetus to licit and illicit drugs. Efforts to direct drug therapy to the fetus have pointed out important gaps in knowledge of the pharmacology of the maternal-placental-fetal-unit (MPFU), whereas other observations illustrated recognized principles of the pharmacology of the MPFU. Many of these principles fit the basic framework of pharmacokinetics: absorption, distribution, metabolism and excretion. Rapid changes in maternal-placental physiology and fetal development during gestation, however, lead to dramatic variations in these processes throughout pregnancy.