Prenatal polymetallic exposure and small for gestational age: A case-control study in Taiyuan, China

Background: Studies focused on independent effects of metals on small for gestational age, failing to account for potential interdependence among metals.

Methods: In this case-control study, we selected 187 pregnant women and 187 matched controls from the First Hospital of Shanxi Medical University. Determination of 12 elements in the venous blood of pregnant women before delivery by ICP-MS. Logistic regression, weighted quantile sum regression (WQSR) and Bayesian kernel machine regression (BKMR) were used to estimate the overall effect and identify important mixture components that drive the associations with SGA.

Results: An increased risk of SGA was associated with As (OR= 1.06,95%CI: 1.01,1.12), Cd (OR= 1.24,95%CI: 1.04,1.47) and Pb (OR= 1.05,95%CI: 1.02,1.08), while Zn (OR= 0.58,95%CI: 0.45,0.76) and Mn (OR= 0.97,95%CI: 0.94,0.99) were protective factors for SGA. In the WQSR positive model, the mixture of heavy metals has a positive combined effect on SGA (OR= 1.74,95%CI: 1.15, 2.62), with Sb and Cd having the highest weights. The BKMR models confirmed that the metal mixture was associated with decreased risk of SGA when the concentration of 12 metals was between the 30th percentile and the 65th percentile, and Zn and Cd had the greatest independent effect. Zn and SGA may not be linearly correlated, higher Zn level may reduce the effect of Cd on the risk of SGA.

Conclusions: Our study suggested that exposure to multiple metals was associated with risk of SGA, and the observed association with multiple metals was dominated by Zn, Cd. Sb exposure during pregnancy may also increase the risk of SGA.