| Objective:Fetal period is a critical and sensitive period for growth and development,and the high-risk factors can lead to abnormal growth and development.Birth weight is an important indicator of fetal growth and development.Low birth weight is closely associated with infant mortality and even the health status in adulthood.Simultaneously,the fetal period also has a strong plasticity and compensatory,the earlier we find adverse factors and to carry out early intervention,the more we can reduce the rate of low birth weight.At present,most of the studies on the influencing factors of low birth weight are aimed at preterm birth.However,the influencing factors of low birth weight are mostly related to preterm birth,and it is not certain whether these factors have an impact on low birth weight when preterm birth is not caused.In addition,the domestic and foreign research on the influence factors of low birth weight are majority focused on a specific type of factors,and there are few studies on the comprehensive effect of various factors,among which the main factors are still unclear.In addition,an increasing number of research have found that heavy metals exposure during pregnancy has adverse effects on birth weight,but most studies on metals have assessed metal exposures individually in contaminated areas.it does not involve the interaction between the joint effects of low-level heavy metal exposure and low birth weight.This study comprehensively analyzed the key influencing factors of low birth weight of fullterm newborns by collecting the data of full-term newborns and pregnant women in a people’s hospital of Jiangxi Province.At the same time,to explore the effect of prenatal exposure to low-dose heavy metals on low birth weight,so as to provide epidemiological evidence for the prevention and control of adverse factors during pregnancy,especially for the mixed exposure to heavy metals.Methods:Taking all 1898 mothers and infants born in a People’s Hospital of a city in Jiangxi province from April 2018 to February 2019 as the research objects,the birth weight,length,head circumference,chest circumference and abdominal circumference of all the newborns were measured.The general demographic characteristics of parents of newborns,regnant women’s health care,life habits,surroundings and nutrition during pregnancy which may affect the neurological development of newborns were obtained by one-by-one questionnaire survey.A total of 1,898 maternal and infant pairs born in a people’s hospital of Jiangxi province from April 2018 to February 2019 who met the inclusion and exclusion criteria was recruited.The birth weight,body length,head circumference,chest circumference and abdominal circumference of all newborns were measured.The general demographic characteristics of parents of newborns,regnant women’s health care,life habits,surroundings and nutrition during pregnancy which may affect the birthweight of newborns were obtained by one-by-one questionnaire survey.At the same time,clinical data such as admission blood pressure,random blood sugar,abdominal circumference,uterine height and blood routine were collected,The blood lead(Pb),cadmium(Cd),arsenic(As)and mercury(Hg)concentrations were measured using an inductively coupled plasma mass spectrometry(ICP-MS)and an atomic fluorescence spectrometry(AFS).Univariate analysis and multiple regression analysis were used to study the influencing factors of full-term low birth weight.Principal components analysis was used to extract the principal components of all factors in order to explore the key influencing factors of low birth weight in full-term newborns.Conditional Logistic regression model was used to analyze and calculate the risk odds ratio(odds ratio,OR)of low dose heavy metals to low birth weight after adjusting for confounding factor,and multivariate regression analysis and stratified analysis were used to explore the interaction of heavy metals.Results:1.Overall condition: among the 1898 newborns,the average birth weight was 3.21 ±0.35(1.90 to 3.95)kg,of which 74 were low birth weight,accounting for 3.9%,and 1824 with normal birth weight,accounting for 96.1%.The gestational age was 39.30 ±1.00(37~41)weeks.Male newborns accounted for 55.4%,and females accounted for 44.6%.2.Analysis of influencing factors of low birth weight: multivariate regression analysis showed that maternal age,pre-pregnancy body mass index(BMI),education level,father’s occupation(management and cadre),gestational weeks and born in spring all decreased the risk of low birth weight.Maternal stay up late during pregnancy,high blood pressure at admission,neonatal cord around neck and maternal blood cadmium and arsenic levels increased the risk of low birth weight(P<0.05).3.Principal component analysis: the significant influencing factors of low birth weight univariate analysis were extracted by principal component analysis,and five main factors were obtained.They are prenatal heavy metal exposure,pregnant women staying up late,parents’ cultural and work,abnormal delivery and maternal hypertension.Taking the above factors as independent variables and low birth weight as dependent variables,multivariate regression analysis showed that prenatal heavy metals exposure was the key risk factor for low birth weight(OR= 1.12,95% CI: 1.06 to 1.19),while parental education and occupation was the protective factor for low birth weight(OR=0.88,95% CI: 0.81 to 0.97).4.Analysis of the association between heavy metal exposure and low birth weight: the geometric mean of four heavy metals in this study population were Pb 16.73(16.29,17.18)mg/L、Cd 1.23(1.19,1.28)mg/L、As 6.71(6.40,7.02)mg/L、Hg 0.96(0.91,1.02)mg/L,respectively.It was close to the blood heavy metal levels of Pb(34.9 ug/L),Cd(0.49 ug/L),As(2.33 ug/L)and Hg(1.41 ug/L)in general population published by the Chinese Center for Disease Control and Prevention.lead exposure was negatively correlated with neonatal body length,chest circumference,head circumference and abdominal circumference,cadmium exposure was negatively correlated with birth weight,body length and head circumference,while arsenic exposure was negatively correlated with birth weight,length,chest circumference and head circumference(P<0.05).Further analysis showed that prenatal exposure to lowdose cadmium increased the risk of low birth weight of full-term newborns to 2.44-fold(95% CI: 1.13-5.27),and was more sensitive to male newborns(P<0.05),while prenatal exposure to low-dose arsenic increased the risk of low birth weight of fullterm newborns to 2.75-fold(95% CI: 1.31-5.78),and was more sensitive to female newborns(P<0.01).5.The interaction between low-dose heavy metal exposure and low birth weight: using conditional Logistic regression model analysis,it was found that there was a synergistic effect of prenatal lead and cadmium exposure on low birth weight(OR=1.01,95% CI: 1.00 to 1.01),and there was an antagonistic effect of prenatal arsenic and mercury exposure on low birth weight(OR=0.94,95% CI: 0.88 to 0.99).After further ternary stratification analysis of blood cadmium and blood mercury concentrations,it was found that blood cadmium in the highest quartile(≥ 1.59 μg/L)could increase the risk of low birth weight caused by blood lead,making the association between blood lead and low birth weight from no statistical significance(P>0.05,OR=1.29,95% CI: 0.92 to 1.80)to statistically significant(P<0.05,OR=1.96,95% CI: 1.02 to 3.75).The highest quartile of blood mercury(≥ 1.65 μg/L)can inhibit the risk of low birth weight caused by blood arsenic,making the association between blood arsenic and low birth weight from statistically significant(P<0.05,OR=1.60,95% CI: 1.13 to 2.27)to insignificant(P>0.05,OR=1.43,95% CI: 0.88 2.32).Conclusions:1.Many factors during pregnancy will affect the low birth weight of newborns.Among them,heavy metal exposure is a key risk factor for low birth weight,and parents’ education and occupation plays an important role in protecting the occurrence of low birth weight.2.Prenatal exposure to cadmium and arsenic in pregnant women may potentially increase the risk of low birth weight and show gender dimorphism.3.Among the risk of low birth weight caused by combined exposure to heavy metal,lead and cadmium exposure showed synergistic effect,while arsenic and mercury exposure showed antagonistic effect. |
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