LONGTERM FOLLOW-UP OF PREMATURE INFANTS

Major Morbidity

The prevalence of neonatal and infant hearing loss (HL) is estimated to be 1.5-6 per 1000 live births. The percentage of this HL due to prematurity has increased dramatically over the past 30 years. In the 1960s, infectious diseases, principally Hemophilus influenzae meningitis, mumps and congenital rubella, were far and away the most common causes of HL, with prematurity accounting for less than 2% of cases.

HL Definitions
Normal - can detect sound between 0-15 dB in the 500-4000 Hz range
Mild HL - detection of sound only at 15-30 dB
Moderate HL - detection of sound only at 31-60 dB
Severe HL - detection of sound only at 61-90 dB
Profound HL - detection of sound only at >90 dB
HL of 30 dB or more will interfere with development of speech and language

By the 1990s, however, with the widespread use of MMR and HIB vaccines, as well as the increased survival of ELBW infants, prematurity accounted for almost 20% of cases. It is now the second most common cause of HL in children, after hereditary HL.

There are many possible reasons for HL in premature babies. Among the most often cited are hypoxia, hyperbilirubinemia, exposure to ototoxic medications and prolonged mechanical ventilation. Another possible mechanism is repeated and prolonged exposure to noise in the NICU, although there is no solid data to support this. Finally, many studies have suggested a role for synergism between the above factors, especially in VLBW infants.

In 2000, the Joint Committee on Infant Hearing published guidelines for the early detection of HL through federally mandated Universal Newborn Screening programs. Physiologic measures approved for such screening included ABRs and OAEs. The goal is to identify all infants with HL before 3 months of age and to institute treatment by 6 months of age.

Babies who fail the original newborn screen should be retested within 4 weeks. A second failure requires referral to a specialized center for confirmation of HL, diagnostic workup and institution of treatment. Additionally, any patient with certain criteria associated with delayed-onset of HL should have regular assessment of hearing every 6 months for 3 years.

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