Low-Birth-Weight Babies at Risk for Subtle Troubles as Teens

NEW YORK, Oct. 2 -- Low-birth-weight infants with no apparent disability can have subtle motor and cognitive deficits that can be discerned at age 16, said investigators here.

The teens were more likely to have these deficits than teens who weighed more than 2,000 grams at birth, according to results of a follow-up study of nearly 500 infants reported in the Oct. 3 issue of the Archives of Pediatrics and Adolescent Medicine.

Scores on the Wechsler Abbreviated Scales of Intelligence test were generally within the normal range but exhibited an overall downward shift, so that on average they were lower for 474 adolescents who weighed less than 2,000 grams at birth, found Agnes H. Whitaker, M.D., of Columbia University and the New York State Psychiatric Institute, and colleagues.

Two factors -- male gender and days of ventilation -- were independent predictors of motor problems, they added.

Likewise social disadvantage and fetal growth ratio predicted lower IQ scores. Neonatal ultrasound evidence of white matter damage predicted both total motor problems and lower full scale IQ score.

The study sample represented a cohort of low-birth-weight babies who were born in or admitted to one of three New Jersey hospitals from Sept. 1, 1984, to June 30, 1987.

The teens were assessed in their homes using the Riley Motor Problems inventory, in which higher scores indicate more motor problems, and the Wechsler IQ test.

Compared with those who had no evidence of abnormalities on neonatal ultrasound screening, those non-disabled adolescents with evidence of germinal matrix and/or intraventricular hemorrhage had higher scores on the Riley oral motor problems scale.

When neonatal ultrasound revealed parenchymal lesions and/or ventricular enlargement, total Riley scores were 3.7 points higher, oral scores were 0.8 points higher, fine motor scores were 0.9 points higher and gross motor scales were 2.0 points higher. Evidence of these lesions also lowered the full scale Wechsler scale by 1.6 points and the Wechsler Performance IQ scores by 2.2 points.

And for every additional week of mechanical ventilation, total and oral motor problem scores were higher by 0.33 and 0.14 points, respectively.

The authors wrote that their "finding that, independent of social risk, specific prenatal, perinatal and neonatal biological risk factors are associated with cognitive and motor outcomes as late as adolescence runs counter to the view that, absent severe disability, early biological risk factors are of little importance in later life."

They cautioned, however, that the study may have failed to adequately assess the impact of early medical complications as contributors to motor and cognitive problems in adolescence.

Nonetheless, they concluded that prevention of white matter injury and reduced need for mechanical ventilation "may be key to improving motor outcomes, whereas the prevention of intrauterine growth retardation (or perhaps impaired head growth) and white matter injury may be key to improving cognitive outcomes."