Background: Maternal calcium absorption increases significantly during the second and third trimesters. This increase in calcium absorption is directly related to maternal calcium intake if found defect in calcium level during pregnancy that causes many problem for mother and fetal. This study Aimed to: assess the knowledge, practice and attitude of pregnant women for effect, of calcium during pregnancy. According to (W.H.O, 2014) the prevalence of hypocalcaemia 50% from women that exposure to osteoporosis. Every four women found one man exposure to osteoporosis. Subjects and Methods: A descriptive design study conducted at both in outpatient clinic for pregnant women, in obstetrics and gynecology department at Benha university hospital. The study included 300 pregnant women by systematic random sample. Tools: (I) An interviewing questionnaire sheet was selected constructed by researcher, tool (II) Modified liker scale to assess women attitude Result: highly statistical significant relation between their knowledge and their personal characteristics. No statistical significant relation between their total practice score and their personal characteristics. No statistical significant relation between his attitude and their occupational status, educational level and social level. Conclusion: low level of knowledge about the important of calcium for fetus, Poor practice toward calcium intake, the calcium supplementation Recommendations: Health educational, Programs regarding nutritional, in the future calcium supplements should be give free.