Association of Maternal Blood Mercury Concentration during the First Trimester of Pregnancy with Birth Outcomes: A Nested Case- Control Study

Abstract

Abstract Background Research has shown that mercury exposure in early pregnancy, as one of the toxic metals, may be related to birth outcomes. Fujian Province, as one of the largest seafood-consuming provinces in China, is at risk of mercury exposure.However, literature on mercury exposure and pregnancy outcomes in Chinese pregnant women is limited. Therefore, the aim of our study was to investigate a possible association between maternal mercury (Hg) exposure and spontaneous preterm birth (SPB) and birth weight. Methods This study was a nested case-control study based on the birth cohort project of Fujian Maternal and Child Health Hospital. The maternal blood mercury concentration of 10-16 weeks of gestation were measured. Paired logistic regression analysis was used to analyze the relationship between blood mercury concentrations and SPB, including the unadjusted model and the model. Estimation of the effect of mercury on birth weight was by smooth spline regression with adjustment for potential confounders. Tests for trend were assessed by modelling the quartiles of mercury concentration as continuous variables using integer values. In addition, the dose-response relationship between mercury concentration and birth outcomes was estimated using restricted cubic spline (RCS) regression. Results A total of 240 participants were enrolled in this study, including 120 control group and 120 SPB group. Except for gestational age, other characteristics were not significantly different in 4 quartile groups (P>0.05). Adjusted smoothed plots suggest a linear relationship between blood mercury concentration and SPB (OR=1.12, 95% CI=0.97-1.28, P=0.124). Higher blood mercury concentration was associated with a higher risk of SPB (Q3 vs Q1: crude OR=2.50, 95% CI=1.16-5.41; adjusted OR=2.54, 95% CI=1.12-5.74). There was no significant association between blood mercury concentration during the first trimester and birth weight (adjusted coefficient:14.51, 95% CI=-5.36-34.38). Conclusions We found that maternal blood mercury concentration was positively associated with SPB in a dose-dependent manner. Further research is needed to investigate the association between the main source of mercury exposure and SPB. and mechanism studies were warranted to explore the underlying pathways.