Indices of body and brain size at birth and at the age of 2 years: relations to cognitive outcome at the age of 16 years in low birth weight infants.

OBJECTIVE

To determine in low birth weight infants the relations of being small for gestational age at birth, microcephalic at birth, low weight for age at 2 years, and microcephalic at 2 years to full scale intelligence quotient (FSIQ) at the age of 16 years.

METHODS

A prospective observational study of 422 of 837 eligible nondisabled low birth weight (<2000 g) adolescents from the newborn brain hemorrhage cohort with weight and head circumference at birth and at the age of 2 years in whom FSIQ was assessed with the Wechsler Abbreviated Scales of Intelligence at the age of 16 years.

RESULTS

In a multiple regression analysis, being small for gestational age (beta = -0.14, p = .02) and microcephalic at 2 years (beta = -0.18, p < .001), but not low weight for age at 2 years or microcephaly at birth, had significant independent effects on 16-year FSIQ. After adjusting for pre-, peri-, and postnatal risk factors for poor cognitive performance, the independent effects of being small for gestational age (beta = -0.13, p = .004) and microcephalic at 2 years (beta = -0.13, p = .01) persisted. In this analysis, birth social risk had the largest significant independent effect on 16-year FSIQ (beta = -0.28, p < .001).

CONCLUSIONS

Being small for gestational age at birth, but not low weight for age at 2 years, and microcephaly at 2 years, but not at birth, were independently related to FSIQ of nondisabled low birth weight adolescents, both with and without control for pre-, peri-, and postnatal risk factors.