Outcomes in Young Adulthood for Very-Low-Birth-Weight Infants

Abstract

Although very-low-birth-weight (VLBW) infants, those weighing less than 1500 g, gained significantly better outcomes when neonatal intensive care became available in the 1960s, studies of later mental development have given mixed results. This longitudinal study enrolled 242 VLBW infants born in the years 1977-1979 who survived and 233 control infants of normal birth weight from the same population. The mean gestational age of the VLBW group at birth was 29.7 weeks. Intelligence testing was performed at age 20 with the Vocabulary and Block Design subtests of the Short Form of the Wechsler Adult Intelligence Scale-Revised. These tests measure verbal comprehension and perceptual-organizational skills, respectively. Academic skills were evaluated using the Letter-Word Identification and Applied Problems subtests of the Woodcock-Johnson Psycho-Educational Battery-Revised. The VLBW and normal-weight groups were sociodemographically similar, but the former group had significantly more chronic conditions than did control group. The major differences were in neurosensory impairment and subnormal height. Fewer subjects in the VLBW group had graduated from high school or obtained a general equivalency diploma by age 20. Although 40% of the VLBW group had repeated a grade, the figure for control subjects was 27%. Fewer VLBW subjects were enrolled in post-secondary studies. These differences remained significant when analysis was limited to those of normal IQ who had no neurosensory impairment. Mean IQ scores were significantly lower in the VLBW group (87 vs. 92, P <.001), and these subjects more often had an IQ less than 70. Control subjects had used alcohol and marijuana more than VLBW subjects, and they more often had had contact with the police. Fewer VLBW subjects had had intercourse, been pregnant, or delivered a live-born infant. Neurodevelopmental expressions of very low birth weight and underachievement at school persist at least into young adulthood. In this study, however, these problems were not associated with increased risk-taking behavior or criminal activity.