| The IHDP was a three-year, multisite, randomized trial of an intervention for low birth weight, preterm infants from diverse ethnic backgrounds. The intervention included pediatric monitoring, referral, follow-ups, home visits, attendance of the infant at a child development center and support group meetings for the parents. Several reports have been written, but two are presented here for illustrative purposes. From the study data, it was found that lower child neonatal health status is a strong predictor of lower cognitive abilities tested at 12, 24 and 36 months (Liaw & Brooks-Gunn, 1993). Neonatal status remained a strong predictor even after the effects of maternal environment and the treatment were taken into account. It was found, though, that the intervention was effective at 36 months in regard to gains in receptive language and visual-motor and spatial skills (Brooks-Gunn, Liaw, & Klebanov, 1992). In fact, cognitive development scores were 7.2 points higher for the intervention group as compared to the control (McCormick, McCarton, Tonascia, & Brooks-Gunn, 1993). Moreover, the effects were most positive for the most at-risk families (i.e., children whose parents had a high school education or less and who were of ethnic minority status; Brooks-Gunn, Gross, Kraemer, Spiker, & Shapiro, 1992). A later study, examining the same sample of children at eight years of age, supported the earlier findings by showing that a subsample that was heavier at birth (though still low birthweight) had higher scores on several cognitive tests (i.e., reading, math, overall IQ) than a lower, low birthweight cohort (McCarton et al., 1997). However, it should be noted that the cognitive test scores of the low birthweight cohort were still within a normal range, based on a nationally representative sample. Other studies have found similar results (e.g., Holmes, Reigh, & Rieff, 1988). A reanalysis of IHDP was conducted by investigators independent from the IHDP research consortium (Baumeister & Bacharach, 1996). The researchers found that birthweight, either directly or interacting with the intervention, was a significant predictor of cognitive outcomes. However, only seven percent of the variance of cognitive outcomes was accounted for by the intervention model. Other factors such as maternal intelligence and the home environment were considered to be important mediating factors for the entire sample. The results from the reanalysis also suggest that cognitive deficits in early childhood (i.e., at three years of age) may regress toward the mean as the child ages, even within two years of the program’s completion (i.e., when the child is five years old). This finding suggests that cognitive deficits may disappear without the need for an intervention. |
