Associations between maternal blood metal concentrations during the first trimester and spontaneous preterm birth: a nested case-control study

Abstract

Abstract Background Few studies have utilized whole blood samples to investigate the association between metal mixture exposure during early pregnancy and spontaneous preterm birth (SPB). We conduct this nested case–control study to investigate both the independent and joint effect of each metal, and identify critical metals in the metal mixture. Results A total of 120 pregnant women with SPB and 120 pregnant women with full-term delivery were selected from the prospective birth cohort. We measured 14 metal concentrations in maternal blood collected during 10–13 weeks gestation. Conditional logistic regression showed that high concentrations of vanadium (V), magnesium, and copper were positively associated with SPB (Adjusted OR = 5.76 (95% CI 2.46–13.53), 3.64 (95% CI 1.64–8.09), 2.88 (95% CI 1.29–6.41), respectively). Moderate manganese (Mn) concentration (50th–75th percentile) group had the lowest estimated OR (Adjusted OR = 0.32 (95% CI 0.13–0.76)). The high level of strontium (Sr) was negatively associated with SPB (Adjusted OR = 0.39 (95% CI 0.17–0.91)). The BKMR model showed a significant positive joint effect of metal mixture exposure on SPB, while V was the most important metal. The non-linear effects of V and lead (Pb) on SPB, and the interaction effects between V–Pb, Sr–Mn were also revealed. Conclusions Maternal blood metal mixtures in the first trimester were found to be positively associated with SPB, with V exhibiting the strongest independent association. Mn had a potential U-shaped association with SPB. Elimination of metal contamination in the environment has a positive impact on maternal and child health.