Effects Of PM_2.5 Exposure In Pregnant Women On Neonatal Birth Weight And The Mediating Role Of Plasma Lead In Taiyuan

Objective:The purpose of the study was to understand the PM_2.5exposure characteristics of pregnant women during pregnancy,the plasma lead level of pregnant women and the birth weight status of newborns in Taiyuan City.Analyze the influence of PM_2.5exposure level during pregnancy on newborn birth weight,and by measuring the plasma lead concentration of pregnant women during pregnancy,to explore whether PM_2.5exposure during pregnancy can affect the related mechanism of neonatal birth weight by affecting the plasma lead concentration during pregnancy,that is,the mediating role of plasma lead in PM_2.5exposure during pregnancy and neonatal birth weight.In order to protect the health of pregnant women and newborns,it is necessary to further clarify the possible mechanism of PM_2.5exposure in early life on the birth weight of newborns and provide the basis for reasonable health care education during pregnancy.Methods:From August 2018 to January 2020,a total of 363 pregnant women who handled the Maternity Care Manual in a hospital outpatient department in Taiyuan City,Shanxi Province were selected to conduct a questionnaire survey by the method of convenient sampling.The survey included the basic demographic characteristics of pregnant women,the history of pregnancy,lifestyle and so on.Blood samples were collected when the subjects entered the cohort,and the plasma lead content in pregnancy was determined by inductively coupled plasma mass spectrometry（ICP-MS）.We collected and recorded the birth information of newborn according to hospital electronic medical record,including newborn sex,gestational age,birth weight,etc.The 24h average concentration of PM_2.5at each monitoring point in Taiyuan during the survey was recorded through the real-time release platform of national urban air quality,the average exposure to PM_2.5in the first or second trimester of pregnancy was estimated based on the data of the pregnant women’s gestational week and the monitoring site where each pregnant woman lived.The data of lead concentration in PM_2.5were obtained from the corresponding detection data of Taiyuan Center for Disease Control and Prevention.Epi Data 3.1 was used to establish the database,and parallel double entry was performed,and the statistical analysis was performed by SPSS 24.0.t/F test,Mann-Whitney U test or Krusal-Wallis H test were used to compare the differences between groups,Spearman rank correlation analysis and multiple linear regression analysis were used to analyze the relationship between PM_2.5exposure concentration during pregnancy,PM_2.5lead concentration,plasma lead concentration and neonatal birth weight.On the basis of correlation analysis,the structural equation model is constructed by using Mplus 8.0.Results:1.Characteristics of PM_2.5exposure during pregnancyThe PM_2.5exposure level of 363 pregnant women was 48.22μg/m³（33.17μg/m³～72.93μg/m³）.Krusal-Wallis H test results showed that the overall distribution of PM_2.5exposure of pregnant women entering the cohort in different seasons was different（H=273.367,P<0.001）,the PM_2.5exposure concentration of pregnant women entering the cohort in winter was higher than that in autumn and summer,the PM_2.5exposure concentration of pregnant women entering the cohort in spring was higher than that of pregnant women entering the cohort in autumn and summer,and PM_2.5exposure concentration of pregnant women who entered the cohort in summer was higher than that of pregnant women who entered the cohort in autumn,and the differences were statistically significant（P<0.05）.2.Characteristics of plasma lead levels in pregnant womenThe plasma lead concentration of 362 pregnant women was 4.15μg/l(1.90μg/l～6.44μg/l.According to Mann-Whitney U test,the distribution of plasma lead concentration among pregnant women with different pregnancies was statistically significant（P<0.05）.As tested by Krusal-Wallis H,the distribution of plasma lead concentration of pregnant women entering the cohort in different seasons was different（H=14.723,P=0.002）,Plasma lead concentration of pregnant women who entered the cohort in winter was lower than that in autumn,and the difference was statistically significant（P=0.001）.Spearman rank correlation analysis showed that there was a positive correlation between PM_2.5exposure concentration during pregnancy and lead concentration in PM_2.5during the same period（r=0.785,P<0.05）.For the pregnant women included in the seasonal stratified analysis,it was found that the plasma lead concentration of the pregnant women who entered the cohort in spring and autumn was positively correlated with the PM_2.5exposure concentration during pregnancy（r=0.283,0.302,P<0.05）,and also positively correlated with the PM_2.5lead concentration（r=0.332,0.279,P<0.05）;The plasma lead concentration of pregnant women entering the cohort in winter was negatively correlated with the PM_2.5exposed concentration during pregnancy（r=-0.217,P<0.05）,and was negatively correlated with the concentration of lead in PM_2.5（r=-0.285,P<0.05）.That is,there is a significant seasonality between the plasma lead concentration of pregnant women and the PM_2.5exposed concentration during pregnancy.3.Characteristics of neonatal birth weightAmong the 363 newborns,the mean birth weight was 3309.34 g.According to ANOVA,the overall difference of neonatal birth weight among pregnant women with different pregnancy weight gain was statistically significant（F=9.856,P<0.001）.The birth weight of neonates whose mothers gained too much weight during pregnancy was higher than that of those whose mothers gained too little weight during pregnancy and those whose mothers gained too much weight during pregnancy,and the difference was statistically significant（P<0.001）.Among 240 pregnant women with normal BMI before pregnancy,there was statistical difference in neonatal birth weight among the three groups of underweight,appropriate weight gain and excessive weight gain during pregnancy（P<0.05）,The newborn birth weight of pregnant women with excessive weight gain during pregnancy was higher than that of pregnant women with appropriate weight gain and insufficient weight gain during pregnancy（P<0.05）.Appropriate weight gain during pregnancy compared with excessive weight gain was a protective factor for macrosomia（RR=0.391,95%CI:0.171～0.891）.4.Analysis of the mediating role of plasma lead concentration in pregnancy between PM_2.5exposure concentration and neonatal birth weightSpearman rank correlation analysis showed that there was no significant correlation between PM_2.5exposed concentration during pregnancy and neonatal birth weight of 363pregnant women（r=-0.073,P=0.166）.According to the gender stratification of newborns,PM_2.5exposure concentration during pregnancy was negatively correlated with newborn birth weight（r=-0.164,P<0.05）.Spearman rank correlation analysis showed that there was no correlation between maternal PM_2.5exposure concentration and maternal plasma lead concentration during pregnancy（r=-0.056,P=0.457）,When the pregnant women were included into the cohort,it was found that when the inclusion season was autumn,the plasma lead concentration during pregnancy of the mothers of newborn girls was positively correlated with the PM_2.5concentration during pregnancy（r=0.326,P<0.05）.Multiple linear regression analysis showed that PM_2.5concentration during pregnancy was a risk factor for plasma lead concentration in mothers whose newborns were female infants and included in the autumn season（β=0.008,P<0.05）.A structural equation model with PM_2.5exposure concentration during pregnancy as the independent variable,maternal plasma lead concentration as the mediating variable,and newborn girl birth weight as the dependent variable was constructed.The model fit well:χ²2=11.577,df=3,χ²2/df=0.009,RMSEA=0.000,CFI=1.000,TLI=1.000,SRMR=0.000.Bootstrap test results showed that there was a direct effect between PM_2.5exposure during pregnancy and birth weight of newborn girls（P<0.05）,and no mediating effect between PM_2.5exposure during pregnancy and birth weight of newborn girls was found（P>0.05）.Conclusion:1.The PM_2.5exposure concentration and plasma lead concentration of pregnant women in Taiyuan during pregnancy showed obvious seasonality.2.The influence of PM_2.5exposure concentration during pregnancy on neonatal birth weight of pregnant women in Taiyuan has gender characteristics,and there is a direct effect on the birth weight of female infants.The higher the PM_2.5exposure level during pregnancy,the lower the birth weight of female infants.In this study,however,we didn’t find the mediating effect of maternal plasma lead concentration on PM_2.5exposure concentration and birth weight of newborn girls.