The HIMAGE study, conducted in partnership with the principal Public Health Insurance Funds of the Loire region, analysed medicinal prescriptions during pregnancy on the basis of a representative sample of 911 pregnant women resident in this region of France. Altogether 93.5% received at least one prescription, with a mean of 10.9 different drugs per woman. The prescriptions were predominantly for drugs of the following Anatomical Therapeutic Chemical (ATC) classes: "alimentary tract and metabolism" (78%); "genito-urinary system and sex hormones" (62%); "nervous system" (62%); and "blood and blood-forming organs" (57%). Iron supplements, paracetamol, folic acid, magnesium, progesterone, oxaceprol, phloroglucinol, amoxicillin, domperidone and diosmine were the most frequently prescribed drugs. In total, 4.6% of the women were exposed to drugs involving a risk during pregnancy: principally nonsteroidal anti-inflammatory drugs (NSAIDs) prescribed from the sixth month onwards. This study revealed a high frequency of prescription of drugs to pregnant women, largely motivated by non-rational and to some extent culture-specific considerations, and it also highlighted the prescription of drugs known to involve risk during pregnancy. These results provide a basis for advising clinicians on the rational and safe use of drugs during pregnancy.