DRUGS DURING PREGNANCY - AN ISSUE OF RISK CLASSIFICATION AND INFORMATION TO PRESCRIBERS

The Swedish system for the classification of fetal risk of drugs was t he first of its kind and was implemented in 1978. Drugs for use in pre gnant women are classified in 4 general categories - A to D. The US Fo od and Drug Administration (FDA) introduced a system in 1979 also usin g the letters A to D, together with an X category. However, the defini tions differ considerably between the FDA system and the Swedish syste m, resulting in a very different allocation of drugs to the respective categories. In the Swedish system, category A includes drugs that hav e been extensively used and/or for which there are reliable clinical d ata indicating no evidence of disturbance of the reproductive process. Category B includes drugs for which data from pregnant women are insu fficient for making any solid estimation of human teratogenic risk, an d classification is therefore based on animal data, with allocation to 3 subgroups. For products in category C, the pharmacological action o f the drug may have undesirable effects on the human fetus or newborn infant. Finally, category D contains drugs for which human data indica te an increased incidence of malformations. The categorisation stateme nt is always followed by a short explanatory text. In contrast to the FDA system, the Swedish system has been well accepted, as judged by an interview study including 934 physicians and pharmacists. We believe that much of the American dissatisfaction may be a consequence of shor tcomings in the category definitions of the FDA system. The FDA system requires an unrealistically high quality of data, e.g. the availabili ty of controlled studies in pregnant women that fail to demonstrate a risk to the fetus are needed for a drug to be assigned to category A. Consequently, the majority of drugs on the US market are allocated to category C, interpreted as 'risk cannot be ruled out'. The distributio n of drugs into the various categories is thus very different between the Swedish and FDA systems. We think that the issue of this debate re flects a fundamental problem related to public health information: how should a large, compounded, changing and difficult to evaluate databa nk be organised before it is made available to professionals and secon darily to lay people?