Investigating drug use in pregnancy. Methodological problems and perspectives.

In this study the use of prescribed drugs before, during and after pregnancy is described. The study is based on data obtained from pharmacy records of 1,948 women who delivered a live-born infant. Different measures to evaluate drug exposure are used. During the nine months of pregnancy 86% of the women used on average 4.2 prescriptions. During the course of pregnancy the use of gastro-intestinal and blood-forming drugs increased, whereas the use of cardiovascular, antiphlogistic and central nervous system drugs decreased. Anti-emetics were predominantly used in the first trimester, and antacids in the last trimester, whereas laxatives were especially used after delivery. The percentage of women who used a treatment for vaginal infections increased from 2 to 7 during pregnancy. Most of the women (73%) received one or more iron prescriptions during the course of pregnancy, however, the prescribed daily dose was low (prescribed daily dose/defined daily dose = 0.6). At least 1% of the women filled a new prescription for anticonceptives in the first trimester of pregnancy. Most likely, our data reflect the general prescribing pattern for Dutch pregnant women who delivered a live-born baby. Therefore, they form a good and detailed base for further studies, for instance, on the exposure to drugs with known or suspected risks or on the use of drugs in patients with chronic concomitant diseases. Such studies may lead to recommendations that may improve prescribing behaviour.