RESUMO
BACKGROUND: Extremely low birth weight (ELBW) has been associated with poor cognitive development in children. We performed this research to establish the association between ELBW and the influence of biological and socioeconomic factors in the intelligence quotient (IQ) score in school-age children. METHODS: This study comprised 184 children with mean and standard deviation of 6.9 +/- 0.8 years of age. The children were divided into four groups based on their birth weight as follows: group A (n = 25), < or =1000 g; group B (n = 52), 1001-1500 g; group C (n = 66), 1501-2500 g; and group D (n = 41), > or =2501 g. The Stanford-Binet after the Terman-Merril Intelligence Scale was used to determine IQ scores. RESULTS: Mean and standard deviation (SD) of IQ values were 95.3 +/- 11.3 for group A, 103.1 +/- 14.4 for group B, 105.1 +/- 12.3 for group C, and 106.8 +/- 11.7 for group D (p = 0.003). Frequencies of children with scores below normal distribution were the following: 28% in group A; 10% in group B; 15% in group C, and 5% in group D (chi(2) = 0.04). Bronchopulmonary dysplasia and parental education were associated with lower IQ scores (p <0.05). CONCLUSIONS: IQ scores of children born with ELBW were significantly lower when compared to children born with a higher birth weight. Additional studies are important to determine whether these neurodevelopmental delays persist into adulthood, and whether there are additional factors associated with catch-up and recovery.