Neonatal rickets; Brittle bones - premature infants; Weak bones - premature infants; Osteopenia of prematurity

Osteopenia is a decrease in the amount of calcium and phosphorus in the bone. This can cause bones to be weak and brittle, and increases the risk for broken bones.

During the last 3 months of pregnancy, large amounts of calcium and phosphorus are transferred from the mother to the baby so that the baby's bones will grow.

A premature infant may not receive the proper amount of calcium and phosphorus needed to form strong bones. While in the womb, fetal activity increases during the last 3 months of pregnancy. This activity is thought to be important for bone development. Most very premature infants have limited physical activity, which may also contribute to weak bones.

Very premature babies lose much more phosphorus in their urine than do babies that are born full term.

A lack of vitamin D may also lead to osteopenia in infants. Vitamin D helps with the body absorb calcium from the intestines and kidneys. If babies do not receive or make enough vitamin D, calcium and phosphorous will not be properly absorbed. A liver problem called cholestasis may also cause problems with vitamin D levels.

Diuretics or steroids can also cause low calcium levels.

Most premature infants born before 30 weeks have some degree of osteopenia, but will not have any physical symptoms.

Infants with severe osteopenia may have decreased movement or swelling of an arm or leg due to an unknown fracture.

Osteopenia is more difficult to diagnose in premature infants than in adults. The most common tests used to diagnose and monitor osteopenia of prematurity include:

• Blood tests to check levels of calcium, phosphorus, and a protein called alkaline phosphatase
• Ultrasound
• X-rays

Therapies that appear to improve bone strength in infants include:

• Calcium and phosphorus supplements, added to breast milk or IV fluids
• Special premature formulas (when breast milk is not available)
• Vitamin D supplementation for babies with liver problems

Fractures will usually heal well on their own with gentle handling, and increased dietary intakes of calcium, phosphorus, and vitamin D. There may be an increase risk for fractures throughout the first year of life for very premature infants with osteopenia of prematurity.

Studies have suggested that very low-birth weight is a significant risk factor for osteoporosis later in adult life. Whether aggressive efforts to treat or prevent osteopenia of prematurity in the hospital after birth can decrease this risk as an adult is unknown.