Clinical pharmacology deals with the pharmacokinetics and pharmacodynamics of various drugs acting in the human system. In pregnancy and lactation, marked physiological variations affect the drug response with a special concern on fetal teratogenesis. Thus, the drugs must be used cautiously in pregnancy, lactation, and in women with childbearing potential. A considerable challenge is faced due to the paucity of available data, as pregnant and lactating women are excluded from most drug trials. The medications must be prescribed keeping in mind the risk vs benefit of the drug administration to the women. Also, the drugs should not be withheld due to their teratogenic effect, during life-threatening emergencies or serious illness to the mother. Hence, the art of drug prescribing in the perinatal period needs careful clinical discretion and a complete understanding of perinatal pharmacology. This chapter gives a bird’s eye view of drug use in pregnancy and lactation.