Auditory maturation and congenital hearing loss in NICU infants

The number of preterm births has increased over the past decades as a result of increasing maternal age and in vitro fertilization (1). At the same time the survival of preterm infants has increased due to advances in perinatal and neonatal care. For example, antenatal corticosteroids for women with threatened preterm delivery, high-frequency oscillatory ventilation and inhaled nitric oxide have now become standard therapy (1). Unfortunately, these improvements sometimes come at a price. Neonatal intensive care unit (NICU) survivors have an increased risk of neurodevelopmental impairment, such as cerebral palsy, cognitive delay, blindness and deafness (2). Infants admitted to the NICU have an increased risk of congenital (present at birth) and acquired hearing loss compared to infants admitted to the well-baby nursery (3). Multiple risk factors have been associated with congenital hearing loss (Table 1) (4). Many of these risk factors occur in daily NICU care. The increased knowledge of the etiology of congenital hearing loss has put the emphasis not only on treating, but also on preventing congenital hearing loss. For example, bilirubin serum levels are kept within a very strict range in NICU infants. While prevention may not always be possible, the increased awareness has resulted in earlier diagnosis and careful counseling. Between 2002 and 2006 the universal newborn hearing screening (UNHS) program was introduced in the Netherlands. This has resulted in earlier identification and referral of infants with congenital hearing loss. Several studies have shown that early and adequate intervention of infants with congenital hearing loss minimizes future problems with speech and language development (5-6). Treatment before the age of six months results in better speech and language development at school age