Fig. 1

Association between prenatal folic acid use and spina bifida risk, by mother’s toenail arsenic concentration

Adjusted for mother’s age (years), place of birth (hospital, clinic, or homes), and secondhand smoke exposure. The cutoff for mother’s toenail arsenic concentrations was defined by the median of study population (0.46 µg/g toenail). Abbreviations: CI, confidence interval; OR, odds ratio