Background Inflammatory bowel diseases (IBD) require complex therapeutic decisions and life choices concerning pregnancy, but little is known about patient's knowledge of IBD and its treatment before and during pregnancy. Aim To develop a novel tool (Crohn's and Colitis Pregnancy Knowledge Score 'CCPKnow') to assess knowledge of pregnancy-related issues in IBD. The validated tool was then applied to determine knowledge in patients. Method Discriminate ability of 'CCPKnow' was validated in four groups with different levels of IBD knowledge. Reliability and readability were tested by Cronbach-α and Flesch-Kencaid. Construct validity was subsequently assessed against general IBD knowledge (CCKnow) in 145 women with IBD. Associations between patient factors and knowledge were studied. Results Median CCPKnow scores differed significantly between the validation groups (P < 0.001). CCPKnow displayed excellent internal consistency, reliability (Cronbach-α 0.94), readability (reading age 9 years) and close correlation with CCKnow (Spearman's ρ 0.64; P < 0.001). Of 145 patients, 44.8% had poor, 27.6% adequate, 17.3% good and only 10.3% very good knowledge. Better knowledge was associated with Caucasian ethnicity, higher income, having a partner, having children, Crohn's and Colitis Association membership, longer disease duration and Crohn's disease. Conclusions Crohn's and Colitis Pregnancy Knowledge Score, a novel knowledge assessment tool of pregnancy and IBD, demonstrated excellent test characteristics. We found that nearly half of the women with IBD had poor knowledge, identifying a pressing need for better education.