Effect Of Exposure To Trihalomethanes In Drinking Water During The First Trimester On Pregnancy Outcomes And The Factors Influencing Internal Exposure

Objective: Toxicological studies suggest that prenatal exposure to disinfection by-products trihalomethanes(THMs)in drinking water are associated with adverse pregnancy outcomes.However,results from epidemiological studies are inconsistent.We conducted this prospective cohort study to investigate the associations between exposure to THMs during the first trimester and pregnancy outcomes,and identify predictors of blood THMs levels.Methods: We conducted this cohort study in Xiaonan Maternal and Child Care Hospital in Hubei,China.A total of 957 pregnant women who presented to the hospital for prenatal care during their first trimester of pregnancy(<14 weeks)were recruited for the study from March 2015 to May 2016.Headspace solid-phase micro-extraction gas chromatography(SPME-GC)was used to determine the concentrations of four THMs in the blood,namely chloroform(TCM),bromodichloromethane(BDCM),dibromochloromethane(DBCM),and bromoform(TBM).After delivery,the related indicators of birth outcome were measured.We used multivariable linear regression models to analyse the associations between exposure to THMs during the first trimester and pregnancy outcomes and identify the factors influencing blood THMs levels at first trimester.Results: 1.The detection rate of the four kinds of THMs(TCM,BDCM,DBCM,and TBM)in the blood of 957 first-trimester pregnant women were 89.7%,75.2%,40.6%,and 39.4%,with the geometric mean of 8.8ng/L,0.8ng/L,0.7ng/L,and 2.7ng/L,respectively.All correlation coefficients(rs)were statistically significant among the blood THMs,except for BDCM and TBM.2.Multivariable linear regression analysis showed that elevated blood Br-THMs(sum of BDCM,DBCM and TBM)during the first trimester was associated with reduced birth weight(β=-97.04,95%CI:-183.17,-10.91,P=0.03).We also found that elevated blood TTHMs(sum of Br-THMs and TCM)was suggestively associated with reduced gestational age(P=0.07).3.The concentration of blood TCM was positively associated with drinking water intake(P<0.01).The concentration of blood BDCM was positively associated with drinking water intake,alcohol drinking and the number of parturition(P<0.01;P<0.01;P=0.03),whereas negatively associated with the time of passive smoking(P<0.01).The concentrations of blood Br-THMs was positively associated with drinking water intake(P<0.001),whereas negatively associated with autumn and winter sampling(P=0.03).The concentrations of blood TTHMs was positively associated with drinking water intake(P<0.001)and the number of parturition(P=0.03),whereas negatively associated with the time of passive smoking(P=0.05).Conclusions: We found that elevated maternal blood Br-THMs level during the first trimester were associated with decreased birth weight,suggesting that there are potential health risks of exposure to THMs during early pregnancy.Our results indicate that water intake,the time of passive smoking,alcohol drinking,sampling season and the number of parturition may affect maternal THMs exposure level during early pregnancy.The identification of these influencing factors is of great importance in reducing THMs exposure during pregnancy and preventing adverse pregnancy outcomes further.More attention should be paid to these factors in the subsequent epidemiological studies about THMs population exposure and health risk assessment.