A Study On Correlation Of Small For Gestational Age And Ambient Air Pollution In Different Standards

ObjectiveSmall for gestational age（SGA）indicates that the birth weight is lower than the10th percentile of the normal average weight of the same gestational age.More and more epidemiological research results suggest that maternal exposure to a certain concentration of ambient air pollutants will have adverse effects on the fetus,and adverse pregnancy outcomes mainly include low birth weight,premature birth,and small for gestational age.There are few researches about the effects of air pollutants exposure on SGA at home and abroad.The reasons are as follows:The conclusions are also inconsistent.The number of samples was small.There are few air pollution variables studied.The study is not sufficient.And the definitions are inconsistent between the 10th and 90th of each gestational week.The difference in cut value of several hundred grams affects the diagnosis of SGA.Therefore,in order to explore scientifically the influence of air pollutants on SGA in Guangdong Province and determine the sensitive exposure time window,we hope to achieve the follow goals:1.Draw the birth weight percentile of gestational age in singleton live births in Guangdong Province and make reference value standard（referred to as Guangdong Province standard）,which is compared with the standard of China Newborn Collaboration Network（referred to as China standard）;2.Through the sampling method,we can determine the relationship of the maternal outdoor air pollutants exposure on SGA under two different standards.We can provide a basis for better assessment of the relationship between air pollution and adverse health effects,and give intervention and management of SGA.Methods1.Using the medical certificate management information system of birth in Guangdong province from Jan 1st,2014 to Dec 31th,2016,we used the GAMLSS method to draw the birthweight percentiles by sex and gestational age and establish a reference standard for birthweight percentiles by gestational age.2.Using the data of birth certificate system of Guangzhou,Shantou,Yangjiang and Shaoguan during 2014²016,we used the methods of Linear Chi-Square tests to compare the differences in the prevalence of SGA between male and female infants,maternal age group,maternal nationality and delivery mode,and found out the general factors which affect SGA in four cities.3.Using atmospheric pollution data from the web site:http://www.pm25.in and the data about the address of the pregnant woman and the date of birth of the newborn,we can calculate the average exposure level of each pregnant woman during pregnancy.A case-control study was used to classify newborns according to Guangdong Province standard and China standard.Birthweight below the 10th centiles according to the birthweight percentile reference standard were SGA group and the rest were control group.Logistic regression to analysis the effects of average pollutant concentrations(PM_2.5,PM₁₀,CO,NO₂,SO₂,and O₃)in the first trimester,the second trimester and the third trimester of pregnant women on SGA in the four cities.Single pollutant adjust model control factors:newborn gender,mother’s age,mother’s ethnicity,and delivery methods.Multi-pollutant adjustment model control factors:newborn gender,mother’s age,mother’s ethnicity,mode of delivery,and other air pollutants.The relationship between exposure and SGA risk in pregnant women was evaluated with OR and 95%CI confidence interval.4.The meta-analysis method was used to combine the total effect OR and 95%CI of the exposure of air pollutants in the first trimester,second trimester and third trimester of the four cities,therefore we can assess comprehensively the risk of exposure to air pollutions in pregnant women and SGA in Guangdong Province.Results1.From 2014 to 2016,there were 5,156,173 singleton live births at gestational ages 25-42 weeks,with an average birth weight（3174.68±217.675）g.Of these,4.5%（248,228）infants were premature.Overall,the total incidence rate of SGA in Guangdong Province on the basis of the Guangdong Province standard is 9.96%.And the total incidence rate of SGA in Guangdong Province on the basis of the China standard was 12.74%.2.The multi-pollutant adjustment model based on Guangdong Province standard showed that the exposure of PM_2.5.5 in the first trimester of pregnant women in Guangzhou,Shantou,Yangjiang,Shaoguan had adverse effects on SGA（Guangzhou:OR=1.229,95%CI=1.105-1.336;Shantou:OR=1.198,95%CI=1.014-1.379;Yangjiang:OR=1.214,95%CI=1.073-1.373;Shaoguan:OR=1.336,95%CI=1.089-1.640）.The above mentioned OR values of the multi-pollutant adjustment model based on the China standardweredecreased（Guangzhou:OR=1.199,95%CI=1.089-1.321;Shantou:OR=1.157,95%CI=1.017-1.317;Yangjiang:OR=1.178,95%CI=1.053-1.319;Shaoguan:OR=1.246,95%CI=1.031-1.506）.Exposure of air pollutants in the second and third trimester in four cities did not have such significant effect on SGA.The multi-pollutant adjustment model based on Guangdong Province standard showed that the exposure of NO₂ in the second trimester of pregnant women in Guangzhou,Shantou,Yangjiang,Shaoguan had adverse effects on SGA（Guangzhou:OR=1.208,95%CI=1.065-1.370;Shantou:OR=1.129,95%CI=1.020-1.251;Yangjiang:OR=1.169,95%CI=1.043-1.312;Shaoguan:OR=1.169,95%CI=1.011-1.351）.The multi-pollutant adjustment model based on China standard showed that the exposure of NO₂ in the second trimester of pregnant women in Guangzhou,Shantou,Yangjiang had adverse effects on SGA and the OR values based on the China standard were decreased,respectively.（Guangzhou:OR=1.153,95%CI=1.029-1.293;Shantou:OR=1.121,95%CI=1.021-1.232;Yangjiang:OR=1.137,95%CI=1.025-1.263）.3.The combined effect of meta-analysis of single pollutant adjustment models consistently showed that exposure to air pollutants PM_2.5,PM₁₀,CO,NO₂,and SO₂during the first trimester was a risk factor for SGA.The combined effect of Multi-pollutant adjustment model（Guangdong Province standard and China standard）in the first trimester,pregnant women exposure to air pollutions-PM_2.5 were the risk factors of SGA（Guangdong Province standard:combined effect OR=1.069,95%CI=1.045-1.094;China standard:combined effect OR=1.073,95%CI=1.051-1.096）.The combined effect of Multi-pollutant adjustment model showed that the exposure concentration of NO₂ in the second trimester of pregnancy had an adverse effect on SGA（Guangdong Province standard:combined effect OR=1.067,95%CI=1.036-1.100;China standard:combined effect OR=1.063,95%CI=1.034-1.093）.The combined effect of single pollutant adjustment model and Multi-pollutant adjustment model exposure of air pollutants in the third trimester,there were no statistical differences.ConclusionThe birthweight percentile standard for singleton live birth by gestational age in Guangdong is different from that of the China Newborn Collaborative Network.The effect of air pollution on SGA is affected by the SGA standard.The two standards are consistent that the exposure of air pollutant-PM_2.5 in the first trimester is a risk factor for SGA,and the concentration of air pollutant in the second trimester is correlated with SGA.The early pregnancy is a sensitive period for the effect of air pollution on SGA.The research about SGA and air pollution should uniform the standard of SGA so that we can exclude the bias.