Objective To determine risk factors associated with borderline intelligence during intra-uterine life, delivery and the neonatal periods.

Methods In a case-control study, 200 year one schoolchildren aged 6 years were recruited. A standard IQ test was used for psychometric testing. Cases had a borderline intelligence (75–84 scores) and normal controls had an IQ of 85 or above scores. Cases and controls were matched for gender.

Results Regression analysis showed that mother's illiteracy (Adjusted OR 2.7, 95% CI 1.6 to 4.2, p=0.001), familial history of mental retardation (AOR 2.1, 95% CI 1.4 to 3.5, p=0.002) and maternal drug consumption during pregnancy (AOR 1.7, 95% CI 1.1 to 2.5, p=0.003) were the main adjusted risk factors associated with borderline intelligence in childhood. No significant association was found between adverse birth outcomes including low birth weight and prematurity and borderline intelligence in children.

Conclusions IQ of schoolchildren is affected by both prenatal and postnatal factors as well as social determinants such as parental education. Controlling these factors has important implications for preventive strategies in psychological, maternal and child health programs worldwide.