The strengths of our study include the population-based prospective study design, relatively large sample size for evaluating associations between As and IGF1 and IGFBP3, available information on important covariates that could act as confounders (e.g. nutritional and socioeconomic status, recent infection status), individual As exposure assessment based on urinary As concentrations during early pregnancy and at 9 years of age. The gene discussed is IGFBP3; the disease is infection.