Background Medication use during pregnancy is ex-tremely common and has increased over the past decades.1–3 Unfortunately, no Belgian data are available on the number and type of products used. The aim of the PREVIM-study (Pregnancy related use of vitamins and medication) is therefore to provide a detailed overview of the prevalence of different types of health products’ use among Belgian pregnant women.

Methods All pregnant women, ≥18 years, attending the obstetrics department of the University Hospitals Leuven and understanding Dutch, French or English were asked to complete an online web-survey once between No-vember 2016 and February 2017 (cross-sectional study). The questionnaire consisted of sociodemographic and pregnancy-related questions, questions about the use of health products and questions about medication beliefs and information desire. Support from a study collabo-rator was available. The questionnaire could be finished at home if necessary. The questionnaire was linked with a database consisting of more than 100 000 pictures of available health products in Belgium. A draft Dutch ver-sion was pilot tested in ten pregnant women and the final version was translated into English and French. Approv-al of the Ethics Committee was obtained; participants signed informed consent prior to the study.

Results In total, 379 pregnant women (40,4%0–13 w, 26,4%14–27 w, 33,2%28–40 w), mean age 32 years (range 18–48), participated in the study. Most women were pro-fessionally active (88.9%), of which one-fifth was working in health care. In 14.5% of cases, the pregnancy was the result of a fertility treatment. Almost all women (98,2%) had used a health product in the preceding week; 86.0% had used folic acid or a pregnancy-specific multivitamin; 52% had used a prescription or OTC medication reg-istered in Belgium. In 53.8% of those, it concerned one medicine; 3.56% had used four or more medicines. 64.1% of pregnant women indicated to have used alcohol in the three months preceding the pregnancy; 12.4% were at that time smokers and 2.6% used drugs. Only 34.8% of women mentioned to have changed life style before pregnancy. 91.6% of smokers stopped smoking at the time they realised they were pregnant or later during pregnancy, while 89,6% of alcohol drinkers did so. 6.1% of women had still smoked cigarettes in the week preced-ing the survey; 5.5% had used alcohol and 0.53% were substance-users.

Conclusion Preliminary data from this cross-section-al study show that almost all Belgian pregnant women used one or more health products in the week preceding the survey. Only one third of women adapted life style in the months before pregnancy; most women who quitted smoking or drinking alcohol did it too late.