A Case-Control Study Of Prenatal Cadmium Exposure And Low Birth Weight In Hubei Area

Objectives: Cadmium(Cd), a highly toxic heavy metal, is ubiquitous in the environment. Early studies have investigated the effect of prenatal Cd exposure on birth outcomes, such as low birth weight(LBW), while the results of these studies are inconsistent. This study was designed to evaluate the association between prenatal exposure to Cd and the risk of LBW, and investigate the level of Cd exposure and its relative factors, and finally provide a theoretical basis and intervention strategies for prevention of prenatal Cd exposure and adverse pregnancy outcome.Methods: Based on 1:3 case-control study methods, a total 728 mother-infant pairs(182 LBW cases and 546 matched controls) were selected from the participants enrolled in the prospective birth cohort, in Wuhan and Macheng city, during November 2012 to April 2014. Concentrations of Cd in maternal urine collected at before delivery were measured by inductively coupled plasma mass spectrometry(ICP-MS) and adjusted by creatinine. Conditional logistic regression was used to calculate odds ratios(OR) and 95% confidence intervals(CIs); one-way analysis of variance(one-way ANOVA) and multiple stepwise regression analysis were used to filter out influential factor of maternal urinary Cd levels.Results: Mothers with LBW infants had significantly higher urinary Cd levels(0.55μg/g Cr) compared to the control mothers(0.42 μg/g Cr)(p < 0.05). A significant association was observed between higher maternal urinary Cd levels and risk of LBW [adjusted odds ratio(OR) = 1.91 for the highest tertile, 95% confidence interval(CI): 1.02, 3.60]. The association was more pronounced among female infants(adjusted OR = 2.59 for the highest tertile, 95% CI: 1.22, 5.50) than male infants(adjusted OR = 1.13 for the highest tertile, 95% CI = 0.50, 2.56)(p heterogeneity = 0.81). Maternal urinary Cd levels were not significantly effected by maternal age(β = 0.137, 95% CI: 0.057, 0.216), household yearly income(β =-0.155, 95% CI:-0.291,-0.025) and calcium supplements during pregnancy(β =-0.136, 95% CI:-0.271, 0.000).Conclusion: Prenatal exposure to Cd at current level encountered in Hubei province may potentially increase the risk of delivering LBW infants, particularly for female infants. Increasing maternal age, lower household income and calcium deficiency during pregnancy are important influential factor for an increasing concentration of maternal urinary Cd levels.