| Background:Lead is an important material with neurotoxicity,which may cause permanent harm on children’s intelligence and behavior.Blood lead exposure may have an impact on embryo’s early development of nervous system through transferring across the placenta.Thus,more and more evidences showed that the effects of prenatal lead exposure on children’s early development were heavier than those of postnatal exposure.US CDC had defined a threshold value of 100μg/L as a safe dose for children’s blood lead exposure.However,more and more researches found that there is no safe dose for lead exposure.Human may suffered from lead exposure at any dose.Especially with the decrease of environmental and blood lead exposure,there is a growing concern of researches on toxicology of low-level lead exposure.In the past researches on the toxicology of prenatal low-level lead exposure,a concentration value of 100μg/L was used to dichotomize high-level lead exposure and low-level lead exposure.However,recent domestic surveillances on blood lead exposure during the pregnancy showed that the blood lead concentration in most of pregnant women was less than 100μg/L.The previous studies have not properly reflected the characteristics of low-level lead exposure and its toxicology at this stage. Thus,it is important to have knowledge of current pregnant lead exposure and explore its adverse effects on health,e.g.,toxicology of reproduction and development.Objectives:1.To have knowledge of blood lead exposure during the pregnancy and the source of environmental lead pollution2.To explore the association between blood lead exposure during the pregnancy and pregnant women’s health and fetus’s developmentMethods:This is a prospective cohort study.Pregnant women from some places in Zhejiang Province were recruited as our research participants with content form.They were followed up until their offspring reached 12 months.During the period,blood lead concentration was tested in the early and late pregnancy and was used as a standard to separate low-level lead exposure from high-level lead exposure.The effects of blood lead exposure on pregnant women’s health,fetus’s development and children’s early intelligence and behavior development were compared between high-level lead exposure group and low-level lead exposure group.The research outcomes included the blood pressure and hemoglobin during the pregnancy,which indicated the effects of blood lead exposure on pregnant women; abdominal perimeter and birth outcome,which indicated the effects of blood lead exposure on fetus’s development;and Mental Development Index and Psychomotor Development Index at six-month and twelve-month,which indicated the effects of blood lead exposure during the pregnancy on children’s early development. Statistical methods included paired-samples t’test,Two-Independent-Samples Tests, ANOVA,Chi-square test,General liner models,Binary logistic regression model, one-way repeated measures ANOVA,Mixed effects model.Results:Total 272 pregnant women were recruited as our participants.Among them,211 respondents examined their blood lead concentration during the early and late pregnancy.High-level lead exposure and low-level lead exposure was defined according to the median of blood lead concentration in both two times.There were 87 participants in the low-level lead exposure group and 80 participants in the high-level lead exposure group.1.Blood lead exposure during the pregnancy.The distribution of the blood lead concentrations during the pregnancy was non-normal distribution but the log-transformation of lead concentrations followed normal distribution.The geometric mean of pregnant women in the early and late pregnancy,and their spouse were 31.4μg/L、39.1μg/L and 54.4μg/L,respectively.The blood lead concentration of pregnant women in the late pregnancy was higher than that in the early pregnancy,and the difference was statistically significant.There is a positive correlation between blood lead concentrations of pregnant women and their spouses(r=0.455,p＜0.01). 2.Multivariate analysis on influencing factors of blood lead concentration in the pregnancy showed that female’s educational level,heavy mental contact history before pregnancy and the frequency of eating vegetable were potential influencing factors:Respondents received more education had lower blood lead concentration in the late pregnancy than those less educated;respondents who had a history of contacting heavy mental before pregnancy and who ate vegetable daily had higher blood lead level in the early and late pregnancy than those who did not contact heavy mental and those did not eat vegetable daily.The examination results on the environmental lead showed that local vegetable with mild lead pollution,which might be the potential source of lead exposure among pregnant women.3.There was a liner trend between blood pressure and pregnant week.In the Mixed effects model,the significant difference of blood pressure in the pregnancy between high-level blood exposure and low-level blood lead exposure was not observed.However,there was a trend that high-level blood lead concentration group had a higher systolic and diastole pressure than that of low-level blood lead concentration by the bivariate and multivariate analysis.4.The trend but no statistical significance was found that hemoglobin in the high-level blood lead group was higher than that of low-level blood lead group in the two examinations.5.In the mixed effects models analysis for the repeated measures data of abdominal perimeter,the abdominal perimeter in the high-level blood lead concentration group was 1.42 cm less than that of low-level blood lead group and the difference was statistically significant(p＜0.05).6.The comparison on birth outcomes between high-level blood lead exposure group and low-level blood lead exposure group showed that offspring from high lead exposure group had lower birth weight,shorter body length and smaller head circumference than that from low lead exposure group,but the differences were not statistically significant(p＞0.05).7.The offspring of high-level blood lead group had a higher blood lead concentration than that of low-level blood lead group at six-month and the difference was statistically significant(p<0.05),which indicated that pregnant blood lead exposure may impact children’s early blood lead level.The children’s blood lead level at twelve-month was also higher in the high-level lead exposure group than that in the low-level lead exposure group,and the difference was significant.8.The analysis of the effects of prenatal blood lead exposure on children’s intelligence and behavior development at six- and twelve-month showed that offspring from high lead exposure group had lower Mental Development Index and Psychomotor Development Index score at six- and twelve-month,but the differences were not statistically significant(p＞0.05).Conclusion:1.The blood lead exposure level was rather low in the present study.Environmental lead exposure,especially from food such as vegetable and others might be the major source of lead exposure in the pregnancy2.The present study did not find the significant relationship between blood lead exposure in the pregnancy and some outcomes including pregnant women’s blood pressure,hemoglobin,birth outcomes and children’s early development. However,the trend of adverse effects was observed.The blood lead exposure in the pregnancy might hinder the children’s development in the late pregnancy3.The prenatal blood lead level may influence fetus’ early blood lead concentration. The offspring of high-level blood lead group had higher blood lead concentration than that of low-level blood lead group at six- and twelve-month. |
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