Anemia is a significant global health problem, particularly among pregnant women, and is defined by the World Health Organization (WHO) as hemoglobin (Hb) levels below 12.0 g/dL in non-pregnant women and below 13.0 g/dL in men. During pregnancy, physiological changes—including a 20–30% increase in blood volume—raise the demand for iron and other nutrients necessary for hemoglobin production. Hemoglobin, the oxygen-carrying protein in red blood cells, is essential for meeting the metabolic needs of both the mother and developing fetus. According to WHO and the Centers for Disease Control and Prevention (CDC), anemia in pregnancy is identified when Hb falls below 11 g/dL, with slight variations by trimester. Iron deficiency remains the leading cause of maternal anemia, contributing to adverse outcomes such as preterm birth, low birth weight, and maternal morbidity. This systematic review examines the determinants of anemia during pregnancy, including nutritional deficiencies, socio-demographic factors, infectious diseases, and access to antenatal care. Understanding these risk factors is critical for designing effective preventive and management strategies, thereby improving maternal and fetal health outcomes.