[Drugs and pregnancy].

The evidence of the transplacental transfer of most of the drugs administered to the mother has changed the old concept of the invulnerability of the fetus due to the placental barrier protection. The commonly used drugs act on the fetus by means of two different mechanisms: directly after the placental transfer, and indirectly influencing the utero-placental circulation and maternal homeostasis. Fetal effects can be several and they depend on the type of the drug, dosage, route of administration, gestational age in relation to the fetal ontogenesis, and on the amount of drug which reaches the fetus.