Compared with term-born children, moderately preterm and late-preterm infants are at increased risk of hearing loss and visual impairment, particularly when brain damage occurs in the perinatal period, researchers say

Infants born between 32+0 and 36+6 gestational weeks "form the majority of all prematurely born infants, and morbidity in this group represents a burden on individuals, families, and the healthcare system," Dr. Mikko Hirvonen of Central Finland Hospital in Jyvaskyla told Reuters Health.

"This group of prematurely born infants has been generally considered low-risk, and there are currently no guidelines for follow-up programs for (them)," he said by email. "Few reports have focused on sensory impairments in (these) children."

To investigate, Dr. Hirvonen and colleagues used the Finland national register to study more than one million live-born infants between 1991 and 2008. They defined moderately preterm (MP) as 32+0 to 33+6 gestational weeks and late preterm (LP) as 34+0 to 36+6 weeks.

Sensory impairment and gestational age

As reported online July 17 in Pediatrics, sensory impairments decreased as gestational age at birth increased. Compared with infants born at term, the incidence of hearing loss was seven-fold greater in very preterm (VP) infants, over twofold greater in the MP group, and 1.5-fold greater in the LP group.

With regard to visual impairment, VP (OR 1.94), MP (OR 1.42), and LP (OR 1.31) births predicted an increased risk, as did maternal age of 40 or above (OR, 1.29).

ORs for factors associated with increased risks of both hearing loss and visual disturbance or blindness were: maternal smoking during pregnancy (1.48), being born small for gestational age (1.23), an Apgar score less than 4 at 1 minute of age (1.27), admission to a neonatal unit (1.21), mechanical ventilation (1.75), intracranial hemorrhage (2.13), and convulsions during the neonatal period (2.88).

"It is important to recognize in clinical practice the long-term risks to which LP and MP infants are subject," Dr. Hirvonen said. "The risk of adverse neurodevelopmental outcome should be included in counseling against smoking in pregnant women."

"During the neonatal period, potential morbidities should be detected and timely managed, including metabolic and respiratory problems, as well as feeding difficulties and jaundice," he added.

"There should be guidelines for discharge routines from the birth hospital for MP and LP infants," he said. "The challenge is to recognize, out of a large number of MP and LP infants, those at risk of further long-term neurodevelopmental disabilities and offer this group of children adequate follow-up and potential early interventions."

Dr. Tara Randis, assistant professor of pediatrics and microbiology at Hassenfeld Children's Hospital at NYU Langone in New York City, told Reuters Health by email, "This study and others identify several risk factors for sensorineural impairment, the vast majority of which are unavoidable and related to the medical complications of preterm birth (intracranial hemorrhage, seizures, infection etc.) and the need for prolonged intensive care."

Like Dr. Hirvonen, she noted that smoking "is a potentially modifiable behavior and the risk of harm to the fetus should be discussed with women who are pregnant or are planning on becoming pregnant."

"Clinicians caring for late preterm infants should maintain a low threshold for early referral for evaluation, diagnosis, and treatment of hearing loss and visual impairment," Dr. Randis concluded.