Chapter 45 Iron Deficiency Anemia
PATHOPHYSIOLOGY
Iron deficiency anemia is the most common anemia affecting children in North America. The full-term infant born of a well-nourished, nonanemic mother has sufficient iron stores until the birth weight is doubled, generally at 4 to 6 months. Iron deficiency anemia is generally not evident until 9 months of age. After that, iron must be available from the diet to meet the child’s nutritional needs. If dietary iron intake is insufficient, iron deficiency anemia results. Most often, insufficient dietary iron intake results from inappropriately early introduction of solid foods (before age 4 to 6 months), discontinuation of iron-fortified infant formula or breast milk before age 1 year, and excessive consumption of cow’s milk to the exclusion of iron-rich solids in the toddler. Also, the preterm infant, the infant with significant perinatal blood loss, and the infant born to a poorly nourished, iron-deficient mother may have inadequate iron stores. Such an infant would be at a significantly higher risk for iron deficiency anemia before age 6 months. Maternal iron deficiency may cause low birth weight and preterm delivery.
Iron deficiency anemia may also result from chronic blood loss. In the infant, this may be due to chronic intestinal bleeding caused by the heat-labile protein in cow’s milk. In children of all ages, the loss of as little as 1 to 7 ml of blood daily through the gastrointestinal tract may lead to iron deficiency anemia. Other causes of iron deficiency anemia include nutritional deficiencies such as folate (vitamin B12) deficiency, sickle cell anemia, thalassemia major, infections, and chronic inflammation. In teenaged girls, iron deficiency anemia may also be due to excessive menstrual flow.
INCIDENCE
1. Of infants 12 to 36 months of age, 3% have iron deficiency anemia.
2. Of infants 12 to 36 months of age, 9% are iron deficient.
3. Incidence of iron deficiency and iron deficiency anemia among adolescent girls is 11% to 17%.
4. The age range of peak incidence for iron deficiency anemia is 12 to 18 months.
5. Prevalence rates of iron deficiency are higher among children living at or below the poverty level and among African-American and Mexican-American children.
6. Of infants fed only non–iron-fortified formula or cow’s milk, 20% to 40% are at higher risk for iron deficiency by age 9 to 12 months.
7. Of breast-fed infants, 15% to 25% are at higher risk for iron deficiency by age 9 to 12 months.
8. The leading cause of anemia in infants and children in the United States is iron deficiency. There was a significant increase in iron deficiency anemia in the United States in the 1990s.
9. Iron deficiency is the most common nutritional deficiency in the world. It is estimated that 20% to 25% of infants worlwide are affected by iron deficiency anemia.
COMPLICATIONS
1. Growth and development: developmental delays (birth to 5 years of age), decreased attention span, decreased social interactions, decreased performance on developmental tests
2. Muskuloskeletal: poor muscular development (long-term)
3. Gastrointestinal: contribution to lead poisoning (decreased iron enables gastrointestinal tract to absorb heavy metals more easily)
4. Nervous system: increased incidence of cerebral vascular accident in infants and children
