Figure 1.

Flow diagram describing study design and exclusion criteria. Footnotes: ^a95% of children in the Oklahoma Birth Defects Registry linked with a birth certificate. All birth records without a linked congenital anomaly record were classified as non-congenital anomalies. ^bExclusion criteria listed in order of exclusion. ^cWe conducted sensitivity analysis including zipcode level geocodes. ^d29 children have more than one included congenital anomaly.