LOW-BIRTH-WEIGHT AND THE RISK FOR MENTAL-RETARDATION LATER IN CHILDHOOD

Data from the population-based Metropolitan Atlanta Developmental Disa bilities Study were used in a case-control study to assess the associa tion between low birthweight and mental retardation (intelligence quot ient less than or equal to 70) among 10-year-old children who were bor n in 1975 or 1976. Children with mental retardation were identified fr om existing records at multiple sources and control children were sele cted from public school rosters. Data on birthweight and other covaria tes (sex, birth order, maternal age, maternal race, maternal education and gestational age) came from birth certificates. We used multiple l ogistic regression modelling to obtain adjusted odds ratios for mental retardation, with normal birthweight children (those weighing greater than or equal to 2500 g) as the referent group. For low birthweight c hildren as a whole, the odds ratio for mental retardation was 2.8 (95% CI 1.9-4.2). The risk was higher for very low birthweight (<1500 g) c hildren than for moderately low birthweight (1500-2499 g) children, an d higher for severe mental retardation (intelligence quotient <50) tha n for mild mental retardation (intelligence quotient 50-70). Adding ge stational age to the models revealed that normal birthweight children who were born preterm also were at increased risk of having mental ret ardation at age 10 years.