Introduction: Pregnancy is a physiological process, woman's normal nutritional requirement increase during pregnancy to meet the needs of the growing fetus and the maternal tissues. Aim: To assess the effect of nutrition on pregnant women's weight. Subjects and Method: Descriptive research design used in four health units which selected by random sample; (450) pregnant woman included in the study. Study Tool: consisted of three parts; part (1): Socioeconomic scale. Part (2): Anthropometric measurements (weight and height). Part (3): Knowledge about nutrition of pregnant women. Results: There was a statistically significant difference between nutritional elements and maternal weight in all visits (four) and 73.3% had poor knowledge. Conclusion: There was poor knowledge among pregnant women regarding nutrition during pregnancy. Also there was a relationship between nutrition and maternal weight gain during visits of follow up. Recommendation: Health education program is needed to increase awareness of pregnant woman about effect of nutrition on maternal weight gain during pregnancy.