Although the mortality rate for very preterm infants has improved, little is known about long-term developmental outcomes. A previously published study described developmental outcomes of preterm infants at 30 months of age. Marlow and colleagues followed up with the cohort at six years of age.
The original cohort included 308 British and Irish infants born extremely prematurely (i.e., 25 weeks’ gestation or earlier). All were alive at six years of age, and 241 were eligible for the study. Each child in the preterm group was matched with a full-term classmate; these children made up the control group. Children were clinically evaluated and tested by developmental pediatricians and psychologists who were blind to the neonatal histories of the participants.
The children were classified by severity of disability (i.e., severe, moderate, mild, and none), according to cognitive ability, neuromotor function, vision, and hearing. Twenty-four percent had severe disabilities at 30 months. Severe disability was defined as highly caregiver dependent, nonambulatory cerebral palsy, blindness, severe hearing loss, or an IQ more than three standard deviations below the mean. Moderate disability was defined as some caregiver independence, ambulatory cerebral palsy, correctable hearing loss, impaired vision, or an IQ two to three standard deviations below the mean. Mild disability was defined as neurologic signs with minimal impairment.
Extremely preterm children were 24 percent more likely to have moderate disability and 22 percent more likely to have severe disability at six years of age compared with the control group. Overall, 80 percent of the preterm group had some level of disability. Cognitive impairment was the most common disability (41 percent). Extremely preterm boys were more likely to have a disability than preterm girls. In contrast, only two children in the control group had moderate disability, and none had severe disability. Severe disability at 30 months of age significantly predicted a child’s condition at six years of age—86 percent of children who were severely disabled at 30 months were moderately or severely disabled at six years.
The authors conclude that extremely pre-term children have greater cognitive and neurologic impairment at school age compared with their full-term classmates. Researchers will need to follow the preterm group in this study to evaluate the academic outcomes of those who had normal cognitive scores.