Objective: To describe the off-label medication use in a cohort of pregnant women. Material and methods: We performed a multicenter prospective longitudinal observational study in the Haute-Vienne department (France) called the NéHaVi cohort (“Né en Haute-Vienne” meaning “born in Haute-Vienne”). Women who had given birth to a viable baby in one of three maternity wards in the Haute-Vienne were included in the study after giving their informed consent. Data on the progress and outcome of pregnancies, childbirth, and drug or toxic exposure during pregnancy were collected. Drugs were classified, according to the labeling of the summary of product characteristics (SmPC) regarding the use in pregnancy, as follows: on-label, off-label at risk, and off-label contra-indicated. Results: During... their pregnancy, the 397 included women gave birth to 400 viable babies (209 boys, 191 girls, 3 sets of twins). All women had used at least 1 health product: 3,533 (92%) drugs, 298 (7.5%) homeopathic products, and 18 (0.5%) herb derivatives. The mean number of different drugs taken was 8.9 ± 5.3 (min 1, max 31). All pregnant women used at least 1 drug either with a license or considered as safe to take during pregnancy. Among the 2,538 (71.6%) on-label drugs, the most frequently used were analgesics (n = 611, 24.1%) (acetaminophen (n = 566)), antianemia preparations (n = 528, 20.8%), drugs for functional gastrointestinal disorder (n = 269, 10.6%), vitamins (n = 192, 7.5%), drugs for acid-related disorders (n = 148, 5.8%), and antibacterials (n = 118, 4.6%). In total, 321 (80.9%, 95% CI: 77.0 – 84.7) pregnant women used at least 1 off-label drug; and more precisely, 285 (71.8%, 95% CI: 67.4 – 76.2) used at least 1 off-label high-risk drug, and 189 (47.6%, 95% CI: 42.7 – 52.5) at least 1 contra-indicated drug. Among the 995 off-label drugs (28.2%), 760 (21.5%) were considered high-risk, including vasoprotectives (n = 156, 20.5%) (treatment of hemorrhoids (n = 147)), antithrombotic agents (n = 91, 11.6%) (heparins (n = 88)), and calcium channel blockers (n = 88, 11.6%). Lastly, 235 (6.7%) off-label drugs used were contraindicated medications (non-steroidal anti-inflammatory drugs during the 3rd trimester (n = 231)). Five babies were born with malformations not related to the drugs used during pregnancy. Conclusion: We showed for the first time the magnitude of off-label prescription during pregnancy in France. Women and health professionals should be made more aware of the potential drug-induced risk during pregnancy. Drug adverse effects during pregnancy should be evaluated through an improved notification in pharmacovigilance and appropriate pharmacoepidemiologic studies in order to change SmPC labelings as early as possible, when necessary.