Effect of maternal blood heavy metal level on brain-derived neurotrophic factor and pregnancy outcomes among Myanmar migrants in Samut Sakhon province, Thailand

Abstract

BACKGROUND: Lead, mercury, cadmium, and arsenic are the priority heavy metals of major public health concern in developing countries. Thailand is a newly industrialized country raising high human workloads of migrant workers form neighbored countries, mostly Myanmar. Exposure to these metals can cause cognitive impairment and depressive disorders through an effect on brain-derived neurotrophic factor (BDNF), which is an important biomarker of pregnancy. Pregnancy outcomes including preeclampsia, preterm birth and low birth weight are major burdens for maternal and child health. Although a number of prior studies have examined the effects of heavy metals on pregnancy, there are few studies focused on migrant population. The aim of this study was to examine the association between maternal blood heavy metals concentrations and BDNF levels and pregnancy outcomes among Myanmar migrants in Thailand.

METHODOLOGY: This study was a birth cohort study conducted at the antenatal care clinic of the hospital from July 2018 to April 2019. A total of 119 pregnant Myanmar migrants carrying a single viable fetus of less than 14 weeks of gestation who had stayed within the industrial plant at least 3 months before were recruited in first trimester. The socio-demographic characteristics and health behaviors of the patients were assessed using a self-report questionnaire. Blood samples were collected in first trimester and third trimester. Maternal blood heavy metal (Pb, Hg, Cd, As) concentrations were measured using an inductively coupled plasma mass spectrometer, and plasma BDNF levels were measured using an enzyme-linked immunosorbent assay. Multivariate binary logistic regressions and multiple linear regressions were modeled to evaluate the associations between these factors.

RESULTS: A total of 72 pregnant women were completed the study. Median (interquartile rank: IQR) concentrations were as follows: BDNF: (64.60 [15.60]/18.27 [23.40]) μg/L, Pb: (27.40 [13.80]/19.90 [11.40]) μg/L, Hg: (6.20 [5.60], 2.60 [2.00]) μg/L, Cd: (0.91 [0.85]/1.06 [0.46]) μg/L, and As: (4.00 [1.10]/3.40 [1.40]) μg/L. We categorized the concentrations into high (≥ median) and low (<median) groups for binary logistic regressions. After adjusting for potential confounders, patients with a high blood As in first trimester had a 2.6-fold increased risk (aOR = 2.603, 95% CI: 1.178, 5.751) of low plasma BDNF in early pregnancy. Diastolic BP in third trimester was higher in every unit of increased third trimester blood Pb concentrations (β = 2.766, 95% CI: 0.026, 5.506). However, there were no significant associations between heavy metals and preeclampsia, preterm birth or low birth weight.

CONCLUSIONS: The present findings demonstrate that pregnant women with higher blood As levels were more likely to have lower BDNF levels in early pregnancy. Pregnant women with high blood Pb have more risk of lower blood pressure in late pregnancy. Public health interventions to address Pb and As exposure should be promoted to improve the health of Myanmar migrants