DALLAS — Early recognition of high-risk infants and excellent nutrition are the best treatments for osteopenia of prematurity, Dr. Charles P. McKay said at a conference sponsored by the American Society for Parenteral and Enteral Nutrition.
Premature infants are at risk for osteopenia of prematurity, or neonatal rickets, due to insufficient calcium and phosphorus accrual before birth, said Dr. McKay, director of the bone and mineral program at Alfred I. duPont Hospital for Children, Wilmington, Del.
Left untreated, children can have fractures, rachitic changes, and shorter stature later in life, he said. Infants born prior to 28 weeks' gestation are at highest risk for osteopenia, which is usually diagnosed at age 2–4 months. The skeleton of at-term infants contains, on average, 25 g of calcium and 13 mg of phosphorus. Total bone calcium at 26 weeks' gestation, however, is just 5 g and accrues exponentially until term.
Premature infants, therefore, should receive formula or breast milk fortified with calcium (200–230 mg/kg) per day, phosphorus (110–123 mg/kg per day), and vitamin D (400 mg/day) to encourage normal bone growth. Fortified milk should be started when the infant tolerates 20–30 mL/kg per day of unfortified milk or breast milk. Preterm infant formulas or fortified human milk should be continued until the infant is aged 6 months or the infant's growth rate is within the normal range, said Dr. McKay.
Length and weight should be followed carefully, he noted. Calcium, phosphorus, and alkaline phosphatase should be measured every 1–4 weeks, depending on growth. “Be careful of ratios,” he warned. “The infant can develop hypercalcemia, or if [minerals are] out of balance, they won't be absorbed. If you see hypercalcemia in an infant, the first thing you should suspect is low phosphorus.”
Daily passive range of motion exercises increase bone mineral density Dr. McKay noted, adding that he recommends extension, flexion, and range of motion exercises of upper and lower extremities, taking care to avoid movements that could cause fracture or stress.
Osteopenia of prematurity is usually diagnosed using lab results and radiologic tools. Low phosphate or high alkaline phosphatase is an indication of osteopenia. A radiologic diagnosis involves right forearm and chest x-rays to check for incidental fractures, or lucency of cortical bone, or bone density measurement with dual-energy x-ray absorptiometry or ultrasound.
Follow-up studies show low bone density persists until age 8–12 years; however, incidental fracture rates are no higher than for the rest of the population.