Drugs during pregnancy: an issue of risk classification and information to prescribers.

The Swedish system for the classification of fetal risk of drugs was the first of its kind and was implemented in 1978. Drugs for use in pregnant women are classified in 4 general categories--A to D. The US Food and Drug Administration (FDA) introduced a system in 1979 also using the letters A to D, together with an X category.

Drug use during pregnancy and breast-feeding. A classification system for drug information.

Since 1978 the Swedish catalogue of registered pharmaceutical specialties (FASS) has carried a special section entitled "Pregnancy and breast-feeding" in each product presentation, intended to form an aid for the prescription of drugs to women during childbearing and lactation. After a brief review of transplacental transport and milk secretion, reproduction-toxicology studies in animals, and methods for clinical evaluation of drugs for use during pregnancy, the classification system is presented. On the basis of available data with regard to effects on early and late stages of pregnancy and labour, all the pharmaceutical specialties concerned are assigned to one of the following pregnancy categories: A, B 1, B 2, B 3, C or D.