Drug development for use during pregnancy: impact of the placenta

Drug development for obstetrics occurs via an informal process of migration from use in adults, irrespective of the therapeutic target; mother, placenta or fetus. This informal process means that use during pregnancy is off-label, with dosing, pharmacokinetics, pharmacodynamics, safety and efficacy not described in regulatory documents or product labels. This is a special concern owing to the complex physiological, cellular and molecular changes that occur across pregnancy. In addition, special attention must be given to the placenta owing to its role in transport between mother and fetus, and metabolism, as well as vulnerability to toxicity. This article will consider how maternal physiology changes and impacts drug disposition with emphasis on the role of the placenta in drug development.