Abstract Background Unhealthy prenatal lifestyle behaviours are associated with adverse pregnancy outcomes, but little is known about what motivates women to comply with preconceptional lifestyle recommendations or consciously plan their pregnancy. Therefore, the objective of this study is to explore the associations between preconceptional lifestyle behaviours, health beliefs and pregnancy planning among Dutch pregnant women. Methods In this cross-sectional study based on the data of the APROPOS-II study, 1,077 low-risk pregnant women were eligible for inclusion. Preconception lifestyle behaviours and actively preparing for pregnancy were assessed in relation to planned pregnancies (based on the London Measure of Unplanned Pregnancies) and health beliefs (14 statements). The following preconceptional lifestyle behaviours were assessed through a self-administered questionnaire in the first trimester of pregnancy: fruit intake, vegetable intake, caffeine intake, (second-hand)smoking, alcohol intake, folic ...