A prospective study of arsenic and manganese exposures and maternal blood pressure during gestation

Background: Pregnancy is a sensitive time for maternal cardiovascular functioning and exposures to arsenic or manganese may adversely affect blood pressure (BP).Objectives: This study examined the associations between arsenic and manganese exposures and maternal BP measured during pregnancy. Effect modification by pre-pregnancy body mass index (BMI) was evaluated.Methods: Pregnant women (N = 1522) were recruited for a prospective cohort study in Bangladesh (2008-2011). Exposure to arsenic and manganese was measured in drinking water at <16 weeks gestation and toenails at onemonth postpartum. Systolic and diastolic BP were measured monthly. Linear mixed models estimated mean BP and differences in mean BP over gestation for arsenic or manganese exposures and adjusted for covariates. Results: Arsenic levels had an increasing dose-response association with maternal BP after 25 weeks gestation. Effect modification was observed for BMI. Participants with lower BMI (<23 kg/m2) exposed to 50 mu g/L arsenic had 2.83 mmHg (95% CI:1.74-3.92) greater mean systolic and 1.96 mmHg (95% CI: 1.02-2.91 mmHg) diastolic BP compared to those exposed to < 1 mu g/L arsenic at 40 weeks gestation. Participants with higher BMI (>= 23 kg/ m2) showed a greater mean systolic BP of 5.72 mmHg (95% CI: 3.18-8.27 mmHg) and diastolic BP change of 6.09 mmHg (95% CI: 4.02-8.16 mmHg) at 40 weeks gestation when exposed to 50 mu g/L compared to < 1 mu g/L arsenic. Participants with lower BMI exposed to drinking water manganese in the 2nd quartile (181-573 mu g/L) had 1.04 mmHg higher mean diastolic BP (95% CI: 0.01-2.07 mmHg) at 40 weeks gestation compared to those in the 1st quartile (0.5-180 mu g/L).Conclusion: Arsenic exposures during pregnancy were consistently associated with increased average maternal systolic and diastolic BP. The effect of manganese on BP was less consistent.