Do early developmental intervention programs improve neurodevelopmental outcomes in preterm infants?
Early intervention programs improve cognitive performance in preterm infants up to 36 months of age, but no effect can be detected by five years of age. A small effect of early intervention on motor performance was found in infancy, but it did not persist until preschool or school age. (Strength of Recommendation: B, based on inconsistent or limited-quality patient-oriented evidence.)
Cognitive and motor aptitude is associated with gestational age. Infants born before 34 weeks of gestation have three times the risk of impairments in multiple developmental domains compared with term infants.1 At four years of age, about one-third of extremely preterm infants (i.e., delivered before 28 weeks of gestation) have evidence of cognitive impairment,1 and 21% of extremely preterm infants show cognitive impairment at six years of age compared with 1% of full-term infants.2 Overall, nearly one-half of extremely preterm infants and more than one-third of very preterm infants (i.e., delivered at 28 to 34 weeks of gestation) have some form of disability.3 Even late preterm infants (i.e., delivered between 34 and 37 weeks of gestation) have a relative risk of 1.13 for disability by three years of age, with persistent increased risk of neurodevelopmental disabilities up to at least seven years of age4 and poorer motor performance than term infants.5
This Cochrane review examined whether early intervention programs improve cognitive or motor outcomes for preterm infants. The study interventions were diverse, including programs of physiotherapy to improve motor skills, parental support and training to improve parent-infant relationships, and neurodevelopmental therapy and infant multisensory stimulation. Levels of infant prematurity and birth weight varied greatly, as did study duration.
Cognitive outcomes were most improved during infancy. Thirteen of the 21 studies reported outcomes at infancy and met criteria for inclusion; only three of the studies reported significant cognitive improvements in the intervention groups. The authors concluded that early intervention programs improve cognitive outcomes in infants, measured by IQ, by nearly one-third of a standard deviation from the mean. By the time the infants reached school age, however, the improvement was only one-fourth of a standard deviation above the mean, failing to meet statistical significance. The largest study, the Infant Health and Development Program, was the only one that followed infants until 18 years of age. It had a follow-up rate of 65% for the 985 participants. No overall differences were noted between the intervention and control groups in cognitive standardized test results by 18 years of age.
The effect of early intervention programs on motor performance was smaller. Ten studies with outcomes at infancy were included in the meta-analysis, of which only one reported a significant difference in motor development between the intervention and control groups. The meta-analysis found a small but significant positive effect of early intervention programs on motor development at infancy. Two of the three studies with follow-up at preschool age reported no significant difference in motor performance between the intervention and control groups, with the third study showing significant motor improvement in the intervention group at 44 months. No significant differences were found in motor performance in the three studies with follow-up at school age. Subgroup analyses revealed that gestational age did not affect the results of early intervention programs on cognitive performance. The effects of gestational age and birth weight were not measured in studies of motor performance.
The heterogeneity of the intensity, focus, settings, and participants in the studies limits the ability to make generalizable conclusions. The results of the meta-analysis were dominated by two large studies, which together contributed nearly one-half of the patients. Finally, there was likely much contamination between the control and intervention groups because infants in the control groups could, and often did, receive services duplicating aspects of the intervention outside of the study. This would have dampened any differences between groups.
The National Perinatal Association recommends that parents of late preterm infants be informed about potential developmental problems related to prematurity.6 Preterm children should be screened regularly for developmental delay,6–8 and parents of preterm infants should be counseled about the options of early intervention programs, their potential positive impact on development, and the limitations of their benefits.