Osteopenia of prematurity (OOP) is a term used to describe a reduction in bone mineral content (BMC) of the preterm infant. Its incidence has been steadily increasing with the survival of more premature neonates as a result of advances in neonatal care. The prevalence of metabolic bone disease is inversely associated with birth weight and gestational age. Up to a third of infants weighing less than one kilogram at birth are osteopenic, more so if they are breastfed.
To develop normally, the skeleton of the fetus requires active materno-fetal transfer of protein, Calcium (Ca) and phosphorus (P). Bone mineralization which occurs predominantly during the third trimester will be inadequate if the fetal increased demands in Ca and P are not met. During pregnancy augmented maternal intestinal absorption and increased skeletal mobilization increase maternal Ca supply to the fetus.
Factors that impede normal bone mineralization include inadequate postnatal intake of vitamin D, calcium (Ca) and phosphorus (P), extended periods of total parenteral nutrition, and also as a side effect of diuretics and corticosteroids prescribed to these infants. Poor bone mineralization is associated with common neonatal conditions. These include sepsis, bronchopulmonary dysplasia, cerebral pathology, acidosis, necrotizing enterocolitis and cholestasis.
Depending on the severity of the demineralization, osteopenia can remain clinically silent or, if severe, can cause bone changes in the form of rarefaction, fraying, cupping, subperiosteal new bone formation or even fractures.