DALLAS — The best treatment for osteopenia of prematurity is prevention by early recognition of high-risk infants and making sure they get the best possible nutrition, 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 accrual of calcium and phosphorus prior to birth, said Dr. McKay, director of the bone and mineral program at Alfred I. duPont Hospital for Children, Wilmington, Del.
If left untreated, this disease can result in fractures, rachitic changes, and shorter stature later in life, he said.
Dr. McKay noted that infants born prior to 28 weeks' gestation are at highest risk for osteopenia, which is usually diagnosed at age 2–4 months. He explained that 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 then accrues exponentially until term.
Premature infants, therefore, should be given 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) for normal bone growth to occur. Fortified milk should be started when the infant is tolerating 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, as well as measuring calcium, phosphorus, and alkaline phosphatase 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.”
Recent studies indicate that daily passive range of motion exercises increase bone mineral density in preterm infants, Dr. McKay noted, adding that he recommends extension, flexion, and range of motion exercises of both upper and lower extremities, taking care to avoid movements that could cause fracture or stress to the infant.
Diagnosis of osteopenia of prematurity is usually made using both 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-ray to check for incidental fractures, or lucency of cortical bone, and/or bone density measurement with dual-energy x-ray absorptiometry or ultrasound. Additionally, Dr. McKay recommended monthly x-rays to look for incremental bone changes.
Findings from follow-up studies show that low bone density persists until at least age 8–12 years; however, the rate of incidental fractures is no higher than for the rest of population, Dr. McKay noted.