Among babies born extremely preterm, risks of moderate or worse neurodevelopmental impairment decreased with each week of gestational age, researchers found.
A meta-analysis showed babies born at 22 to 25 weeks had "a substantial likelihood of developing moderate to severe impairment" at ages 4 to 8 years, according to Gregory Moore, MD, of The Ottawa Hospital General Campus in Canada, and colleagues.
But these risks in moderate to severe impairment declined significantly by 6.5% for each additional week of gestation (95% CI 2%-11%), they wrote online in JAMA Pediatrics.
The authors cautioned that wide confidence intervals at lower gestations and high heterogeneity at higher gestations limit the results. Nonetheless, "knowledge of these data ... should facilitate discussion during the shared decision-making process about care plans for these infants, particularly in centers without their own data," they stated.
Although medical interventions have driven down rates of infant mortality among those born preterm, there is a high prevalence of intellectual disability among those preterm infants.
"For many parents, the chance of their extremely preterm infant surviving with long-term neurodevelopmental impairment is a deciding factor, possibly more important than survival," Moore's group wrote, adding that prior research has not gathered data on rates of neurodevelopmental impairment outcomes in childhood.
The authors conducted a meta-analysis of nine studies to determine the rate of moderate to severe and severe neurodevelopmental impairment in surviving extremely preterm infants at ages 4 to 8, as well as any differences in rates of these impairments based on gestational age.
Severe neurodevelopmental impairment was defined as an IQ score more than three standard deviations below the mean, nonambulant cerebral palsy, no useful vision, or no useful hearing despite amplification. Moderate impairment was defined as an IQ of two to three standard deviations below the mean, ambulant cerebral palsy, little useful vision, or hearing restored with amplification.
Gestational age was classified as completed weeks of gestation, and was used as the basis for association with impairment instead of birth weight "because gestational ages are more applicable for antenatal consultations, avoid the inclusion of more mature but growth-restricted infants, and are the preferred method of reporting outcomes."
Of the nine studies, five had a term-control group. Between all studies, there was no statistically significant difference between the moderate to severe rates of impairment in children born at 22 weeks, 23 weeks, and 25 weeks, but there was a statistically significant difference at 24 weeks (P=0.03).
Moderate to severe impairment risk decreased significantly for each additional gestational week. This association was not significant for severe impairment.
In an accompanying editorial by Mandy Brown Belfort, MD, of Boston Children's Hospital in Massachusetts, Belfort noted that only a small portion of infants as preterm as those included in the data pool survive, regardless of technological support, and that outcomes in the event of survival can also be impacted by other factors, such as poverty or the quality of preschool programs.
She also cautioned that, based on definitions in the study, cognitively normal preemies who were completely deaf were considered severely impaired, adding that context in interpreting the study outcomes were very important for other healthcare professionals.
The study was limited by absent data on survival rates, lack of term-control groups in nearly half of the included studies, and the inclusion of one study with a follow-up rate of less than 70%.
There was also limited generalizability in some study populations, the effect of impairment on quality of life, and limitations in the works used in the meta-analysis.
Belfort added that "placed in the appropriate context, these data will be helpful for neonatologists and particularly for families faced with difficult decisions regarding appropriate care for preterm infants born at the edge of viability."
Primary source: JAMA Pediatrics
Source reference: Moore GP, et al "Neurodevelopmental outcomes at 4 to 8 years of children born at 22 to 25 weeks' gestational age: a meta-analysis" JAMA Pediatr 2013; DOI: 10.1001/jamapediatrics.2013.2395.
Additional source: JAMA Pediatrics
Source reference:Belfort MB "Infants who survive birth at the edge of viability: How are they doing at school age?" JAMA Pediatr 2013; DOI: 10.1001/jamapediatrics.2013.2758.