Objectives To assess whether medication beliefs differ between women who use or not use medication for their somatic chronic diseases during pregnancy and whether this association varies across diseases. Design Cross-sectional web-based survey. Setting Multinational study in Europe. Participants Pregnant women or women with children less than 1 year old from European countries and with asthma, allergy, cardiovascular, rheumatic diseases, diabetes, epilepsy and/or inflammatory bowel diseases (IBD). Primary and secondary outcome measure Differences in scores of the Beliefs about Medicines Questionnaire (BMQ). Results In total, 1219 women were included (ranging from 736 for allergy to 49 for IBD). Women using medication for their chronic disease (n=770; 63%) had higher scores on the BMQ subscales necessity (16.6 vs 12.1, p<0.001) and benefits (16.2 vs 15.4, p<0.001), and lower values on the subscales overuse (12.5 vs 13.1; p=0.005) and harm (9.8 vs 10.7, p<0.001) than women not using medication. No significant differences were shown for the concerns subscale (12.5 vs 12.3, p=0.484). Beliefs varied somewhat across diseases but in general more positive beliefs among women using medication were shown. Epilepsy was the disease where less differences were observed between women using and not using medication. Conclusion Women's beliefs were associated with medication use during pregnancy with only small differences across the diseases. Knowing pregnant women's beliefs could help identify women who are reluctant to use medication and could guide counselling to support making well-informed treatment decisions.