Final answer:
The most common cause of iron deficiency in infants is increased demand during rapid growth, along with poor iron stores at birth, dietary insufficiency, and malabsorption issues.
Step-by-step explanation:
The most common cause of iron deficiency in infants is increased demand during rapid growth in infancy and inadequate iron stores at birth, which are more likely in the case of premature or twin pregnancies. Insufficient intake due to a diet low in iron, particularly when a baby transitions from breast milk or formula to solid foods, can also contribute to deficiency. Moreover, poor absorption can occur in malabsorptive syndromes. Since iron is crucial for cognitive and motor development in early childhood, addressing iron deficiency is essential for infant health.