A study of drug utilization in pregnancy in the light of known risks: is there room for improvement?

The prescription records of 1948 Dutch women who delivered a live-born infant during an 18 month period in 1987 and 1988 were set against the Australian classification of drugs with respect to the known or suspected risks in pregnancy. During pregnancy the use of drugs with proven or anticipated foetal toxicity proves to decrease, indicating that the medical profession is relatively well aware of these potential side effects. In the case of antibiotics the fall in the use of potentially toxic drugs is due to a shift to relatively less toxic drugs whereas the decreased use of analgesics and some antirheumatic drugs is not accompanied by replacement by others. Prescriptions for hormonal contraceptives were sometimes actually filled in the first trimester of pregnancy, and the figures suggest that exposure to these products in early pregnancy may not be negligible. The present study shows that in spite of the generally favourable trends, 167.8 out of 1000 women received during the course of pregnancy one or more prescriptions from the higher risk categories (D, C or B3) in the Australian system. By combining such utilization studies with data from registries of birth defects one will be able to develop the fund of knowledge and to ensure that the classification of drugs with respect to their risks in pregnancy is as accurate as it can reasonably be.