Prescribing during pregnancy and lactation with reference to the Swedish classification system. A population-based...

To assess the current prescribing pattern for 15,756 primiparae before, during, and after their pregnancies with reference to fetal and neonatal risk.

A prescription database study with linkage to The Danish Medical Birth Registry from 1991 to 1996. The drug subsidy system in Danish retail pharmacies, made it possible to identify prescriptions by individual use. All 34,334 prescriptions were set against the Swedish classification of risk of drug use in pregnancy and lactation.

During pregnancy, safe (group A), potentially harmful (group B3, C, and D), and non-classifiable drugs accounted for 40.9%, 26.6% and 28.7% respectively. The proportion of women who redeemed drugs was 29.2%, 8.6%, 18.7% and 0.9% from drug groups A, B, C and D respectively. The proportion of prescriptions from high risk groups declined during the course of pregnancy. Postpartum, safe drugs (group I and II), drugs with possible harmful neonatal effects (group III), and non-classifiable drugs accounted for 43.5%, 4.8%, and 35.8% of the prescriptions, respectively.

According to the Swedish classification system, we found that during pregnancy and lactation a high proportion of Danish women were exposed to one or more drugs in high risk groups; furthermore, knowledge regarding their safety for the fetus and neonate was limited for a large proportion of the prescriptions. Current evidence about long-term effects of prenatal exposure stresses the need for long-term follow-up of health and development among exposed children.