What a pregnant woman sees, thinks about, or experiences , such as witnessing a frightening event or seeing a birthmark , can directly mark or deform her unborn child, imprinting these impressions on its body.
Maternal impression theory was widely believed in medieval and early modern medicine but has been completely disproven. Birth defects result from genetic factors, infections (like rubella), nutritional deficiencies, or teratogenic exposures , not from maternal experiences or visual impressions. Modern developmental biology and genetics demonstrate there is no mechanism by which visual or emotional experiences could alter fetal development in this way. The theory persisted because coincidence and confirmation bias created false correlations.