Calcium supplementation during pregnancy is important for mothers, involves an increased demand for calcium to support the optimal growth and development of the fetus. Aim: to evaluate the effect of educational guidelines on pregnant women`s perception regarding calcium supplementation. Design: A quasi-experimental design (one group pre - post-test). Setting: antenatal care clinic at maternal and child health center at Helwan city, Egypt . Sample: A purposive sample of 100 pregnant women in second and third trimesters , with reproductiveages. Pregnant women who had medical contraindications to calcium intake were intentionally excluded from the study. Tools: two assessment tools. Tool (I) A Structured Interviewing Questionnaire three parts: Part (1) general characteristics,Part (2) obstetric history .Part (3): knowledge assessment : to assess women`s knowledge regarding calcium supplementation. Tool (II) Attitude Assessment to evaluate women's attitudes regarding calcium supplementation during pregnancy. Results:more than half of the pregnant women achieved a satisfactory level total knowledge during the post-test contrasting with less than 10%.demonstrated a satisfactory level of knowledge during the pretest, regarding attitude of the pregnant women , nineteen individuals held a negative attitude during the pre-test, while more than half displayed a positive attitude following the implementation of educational guidelines during the post-test. Conclusion: educational guidelines had a positive impact on both the knowledge and attitude of the pregnant women regarding calcium supplementation. This observation supports the research hypothesis .Recommendation : Continuous educational classes to pregnant women to increase awareness regarding the importance of calcium during pregnancy, and how to prevent calcium deficiency.