The Association Of Maternal Urinary Uranium Levels With Birth Outcomes:A Cohort Study

BACKGROUND: Uranium(U)is a heavy metal with both chemical toxicity and radioactivity.In the environment,U can be detected in rocks,soil and groundwater.In recent decades,U has been widely used in nuclear power reactors and nuclear weapons,which has also led to environmental pollution and serious health safety concerns.But there are little data on uranium exposure levels in large sample populations.Recent animal studies have shown that adulthood U exposure can affect the function of various organs,including the intestine,reproductive system,and brain.However,little is known about its association with infants' birth outcomes.Objective: We aimed to investigate the level of U exposure and its relative factors,and the association of maternal urinary Uranium Levels with birth outcomes.Methods: Urine samples of 8500 women were collected before delivery from a birth cohort in Wuhan,China.Urinary U concentrations were measured by inductively coupled plasma mass spectrometry.Independent sample t test and one-way analysis of variance(one-way ANOVA)were used to filter out influential factor of maternal urinary U levels.We used multivariable logistic regressions and linear regression,with adjustment for potential confounders,to evaluate the associations between urinary U concentrations and birth outcomes.Birth outcomes included preterm birth(PTB),preterm premature rupture of membranes(pPROM),low birth weight(LBW),gestational age,birth weight and birth length.Results: The geometric mean of U concentration of the first trimester and the third trimester was 0.03 ?g/g creatinine and 0.07 ?g/g creatinine,respectively.Maternal urinary Cd levels were significantly affected by parity,whether work during pregnancy and drinking water type.In the third trimester,after adjustment for potential confounders,each one unit increase in Log2-unit increase in U concentration(?g/g creatinine),odds ratios(OR)of 1.26(95% CI: 1.16,1.38),1.32(95% CI: 1.17,1.49)and 1.18(95% CI: 1.06,1.30)for PTB,pPROM and LBW was observed.And the oddsratios(OR)[95% confidence interval(CI)]for increasing quartiles of urinary U were 1.28(0.84,1.95)for quartile 2,2.01(1.35,3.00)for quartile 3,and 3.31(2.18,5.02)for quartile 4 for PTB;1.02(0.53,1.94)for quartile 2,2.14(1.21,3.78)for quartile 3,and 3.43(1.90,6.19)for quartile 4 for pPROM;and 1.36(0.86,2.16)for quartile 2,1.93(1.22,3.03)for quartile 3,and 2.79(1.72,4.53)for quartile 4 for LBW.Each Log2-unit increase in U concentration(?g/g creatinine)was negatively associated with 0.44 days(-0.56,-0.32)in gestational age,3.01 g(-8.61,2.59)in birth weight,and 0.01 cm(-0.03,0.01)in birth length.But no significant association of U with LBW was found in the first trimester.Conclusions: To our knowledge,this was the first report demonstrating significant associations between pregnancy maternal urinary U level and adverse birth outcomes.We showed significant associations between prenatal exposure to U and adverse birth outcomes including PTB,pPROM,LBW,and decreased gestational age,birth weight and birth length.And maternal urinary Cd levels were significantly affected by parity,whether work during pregnancy and drinking water type.