[Multicenter study of the use of drugs during pregnancy in Spain (III). Drugs used during the first pregnancy trimester. DUP workshop of Spain].

The Spanish Study on Drug Use in Pregnancy, promoted by the Spanish Society of Clinical Pharmacology, included overall 1,371 women. In this paper we describe the use of medicines during the first trimester of pregnancy. 85% of the drugs taken had been prescribed by the obstetrician. Pregnant women who had used any medicine during this period (n = 753) attended their physician for the first time at a mean of 9.7 weeks (sd = 5.4), while the first visit of non-users (n = 618) took place at 12.5 weeks (sd = 7.0) (p less than 0.001). The percentage of medicines taken as self-medication was only 5% of total. These three findings suggest that drug use during pregnancy is mainly decided by the obstetrician. 11% of pregnant women received at least one medicinal product containing retinol and 5% received iodide, both as vitamin supplementation; these two substances do not have a demonstrated efficacy and their safety for the embryo is very doubtful. Of all women, 15% received pharmacological treatment for nausea and/or vomiting, a proportion which does not seem to be justified according to the existing data on the prevalence of hyperemesis during the first trimester of pregnancy. This study also showed the persistence of an incorrect treatment of threatened abortion.