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

Abstract

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 one-month 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 μg/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 μg/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 μg/L compared to ≤ 1 μg/L arsenic. Participants with lower BMI exposed to drinking water manganese in the 2nd quartile (181-573 μg/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 μg/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.

Keywords: CVD; Cardiovascular disease; Diastolic; Environmental contaminants; Metal exposures; Pregnancy; Systolic; Trimester.

Fig. 1.

Study population for analysis.

Fig. 2.

Predicted mean systolic and diastolic blood pressures over gestational age at five selected concentrations of drinking water arsenic for pregnant women in Bangledesh who have body mass index <23 kg/m² (A1 and A2) or body mass index ≥23 kg/m² (B1 and B2). The five drinking water arsenic concentrations were selected to represent a wide-range of exposures encountered in this population. Estimates are for women located in Sirajdikhan Upazila, secondary school or higher education, 22 years of age, average drinking water manganese intake (5.67 μg/L), and income of 4000–5000+ Taka per month (n = 1169). The models for diastolic blood pressure (A2 and B2) included a quadratic function of gestational age.

Fig. 3.

Predicted mean systolic and diastolic blood pressures over gestational age at quartiles of drinking water manganese for pregnant women in Bangledesh who have body mass index (BMI) < 23 kg/m² (A1 and A2) or body mass index ≥23 kg/m² (B1 and B2). Estimates are for women located in Sirajdikhan Upazila, secondary school or higher education, 22 years of age, average drinking water arsenic intake of 1.03 μg/L, and income of 4000–5000+ Taka per month. Quartiles of drinking water manganese at BMI <23 kg/m2: Q1 = 0.5–180 μg/L, Q2 = 181–573 μg/L, Q3 = 574–960 μg/L, Q4 = 961–5300 μg/L; Quartiles of drinking water manganese at BMI ≥23 kg/m²: Q1 = 0.5–175 μg/L, Q2 = 176–630 μg/L, Q3 = 631–985 μg/L, Q4 = 986–4720 μg/L.