Arsenic Methylation and Body Composition among Pregnant Women in Rural Northern Bangladesh: The Pregnancy, Arsenic, and Immune Response (PAIR) Study

BACKGROUND AND AIM: Arsenic methylation—the conversion of inorganic arsenic (iAs) to less toxic monomethyl (MMA) and dimethyl (DMA) species—could modify the developmental and reproductive toxicity of this metalloid. However, variability in arsenic methylation among pregnant women remains poorly understood. Arsenic methylation efficiency—the percentage of urinary arsenic methylated to DMA (DMA%)—is positively associated with body mass index (BMI) in pregnant women, but BMI is an ambiguous measure of body composition. We estimated arsenic methylation by body fat percentage as well as BMI in pregnant women in Bangladesh. METHODS: We collected spot urine samples from pregnant women (n=784) in gestational weeks 11-17 and measured weight, height, and subscapular and triceps skinfolds. Urinary arsenic was speciated by HPLC-ICPMS. Arsenic metabolism was assessed by…