A Study Of The Associations Between Maternal PM_2.5 And PM₁₀ Exposure During Pregnancy And Term Low Birth Weight

1 BackgroundCurrently,ambient particulate matter(PM)pollution is a severe global issue.Inhalable particulate matter(PM10)and fine particulate matter(PM2.5)pollution has posed great threat to the health of the global population.Chinese government has adopted related measures and the PM2.5 and PM10 levels have decreased in recent years,but they are still much higher than those in developed countries.Thus,the current situation in China is not optimistic.In recent years,given the gradually serious situation of global ambient PM pollution have aroused wide concern,numerous studies exploring the associations between maternal PM2.5 and PM10 exposure during pregnancy and low birth weight(LBW)have been conducted.LBW is one of the common adverse birth outcomes,which can make severe impact on normal development in childhood and adolescent and health status in adulthood,and can also bring heavy economic burden.Therefore,the prevalence of LBW is a serious public health problem.Most of the previous studies found that maternal PM2.5 or PM10 exposure during pregnancy is one of the possible risk factors for LBW.However,these studies usually focused on the impact of maternal PM2.5 or PM10 exposure during the first,the second,and the third trimester on birth weight,thus they reported relatively broad range of time periods as susceptible exposure windows.Besides,the susceptible exposure windows identified in different studies are inconsistent.In addition,the air pollutant monitoring systems for PM2.5 have come into service only in the past few years,thus there are few studies exploring the impact of maternal PM2.5 exposure on birth weight in China.In this study,we aimed to analyze the associations between maternal PM2.5 and PM10 exposure during pregnancy and term low birth weight(TLBW),which can provide scientific evidence for relevant departments to formulate targeted measures of prevention and control.2 Objective1.The study aimed to quantitatively analyze the impact of maternal PM2 5 and PM10 exposure during pregnancy on TLBW.2.The study aimed to explore possible gestational weeks as susceptible exposure windows of pregnant women who were exposed to PM2.5 or PM 10.3 MethodsWe used a 1:4 matched retrospective nested case-control study design,and the study population was puerperae with their infants who delivered at the Jinan Maternity and Child Care Hospital from 2014 to 2017 and the Affiliated Qianfoshan Hospital of Shandong University from 2014 to 2016.Cases were infants with TLBW,which was defined as birth weight<2,500 g at 37-42 completed weeks of gestation and controls were term infants with birth weight>2,500 g but<5,000 g.All of the puerperae who delivered infants with TLBW were searched out in hospital information system of the two hospitals and for each case,four controls were randomly selected and matched by maternal age.Then,their information was typed in pre-designed questionnaires by professional investigators.There are thirteen monitoring stations in urban Jinan and daily concentrations for PM2.5,PM10,NO2,and SO2 are measured continuously,and these data from 2013 to 2017 are obtained on the Shandong Provincial City Air Quality Data Publishing Website.We calculated daily estimated air pollutant concentrations by an inverse distance weighting(IDW)and a time-weighted approach,which can subsequently be used to calculate maternal weekly mean exposure concentrations corresponding to every gestational week.We used distributed lag models(DLM)to explore the associations between maternal PM2.5 and PM10 mean exposure in each gestational week and TLBW.We first built single-pollutant models,and the P25 of PM2.5 and PM10 during the study period were set as the reference concentration while the P75 of them as the targeted concentration,which could present the risk of a pregnant woman delivering an infant with TLBW when her exposure concentrations increased in an IQR.To adjust for the influence of maternal NO2 or SO2 exposure,we then built two-pollutant models to adjust for NO2 and SO2,respectively.Then,the cumulative effects were computed to gain a knowledge that how serious it would be if one pregnant woman has suffered from a constant exposure to a specific air pollutant throughout the gestational weeks of interest,and finally we conducted several sensitivity analyses.4 Results(1)A summary of air pollutants:During 2013 and 2017,the daily mean PM2.5 and PM10 concentration in urban Jinan was(85.9±55.3)?pg/m3 and(161.6±83.1)pg/m3,respectively.The daily mean PM2.5 concentrations were positively correlated with PM10,NO2 and SO2,and the spearman correlation coefficients were 0.90,0.64 and 0.62,respectively.The daily mean PM10 concentrations were positively correlated with NO2 and SO2,and the spearman correlation coefficients were 0.66 and 0.65,respectively.(2)General information of subjects:We included a total of 509 cases and 2036 controls in the Jinan Maternity and Child Care Hospital and the Affiliated Qianfoshan Hospital of Shandong University and median(lower quartile,upper quartile)maternal age were 29(26?32)years.Median(lower quartile,upper quartile)birth weight,gestational week,and height of puerperae of cases were all less than controls[2350(2240?2450)g vs.3400(3150?3650)g,38(37?38)weeks vs.39(38-40)weeks,160(159?164)cm vs.162(160?165)cm],and the differences between the two groups were all statistical significant(P<0.05).Compared to controls,cases were more likely to be female infants,non-spontaneous labor,primiparous,diagnosed with hypertensive disorders in pregnancy,oligohydramnios,abnormal umbilical cord,but were less likely to be anemia.(3)Effect of maternal PM2.5 and PM10 exposure on TLBW:In single-pollutant model,the 26th to 32th gestational weeks were identified as susceptible exposure windows of pregnant women who were exposed to PM2.5 and the effect peaked at the 29th gestational week.Compared to their counterparts in scenarios with a PM2.5 level of 49.8 ?g/m3,the odds ratio(OR)of pregnant women in scenarios with that of 104.0?g/m3 to deliver an infant with TLBW was 1.120(95%CI:1.048?1.197).The 25th to 33th gestational weeks were identified as susceptible exposure windows of pregnant women who were exposed to PM10 and the effect peaked at the 28th gestational week.Compared to their counterparts in scenarios with a PM10 level of 105.0 ?g/m3,the OR of a pregnant women in scenarios with that of 196.1 ?g/m3 to deliver an infant with TLBW was 1.140(95%CI:1.048-1.239).In two-pollutant model adjusted for NO2,the 27th to 32th gestational weeks were identified as susceptible exposure windows of pregnant women who were exposed to PM2.5 and the effect peaked at the 29th gestational week(OR=1.123,95%CI:1.043?1.210).In two-pollutant model adjusted for SO2,the 26th to 33th gestational weeks were identified as susceptible exposure windows of pregnant women who were exposed to PM2.5 and the effect peaked at the 29th gestational week(OR=1.142,95%CI:1.060?1.231).In two-pollutant model adjusted for NO2,the 25th to 31th gestational weeks were identified as susceptible exposure windows of pregnant women who were exposed to PM1O and the effect peaked at the 28th gestational week(OR=1.157,95%CI:1.049?1.277).In two-pollutant model adjusted for SO2,the 25th to 32th gestational weeks were identified as susceptible exposure windows of pregnant women who were exposed to PM10 and the effect peaked at the 28th gestational week(OR=1.154,95%CI:1.052?1.267).(4)Cumulative effects:Combined results of single-and two-pollutant models,the 26th to 33th and the 25th to 32th gestational weeks were identified as susceptible exposure windows of pregnant women who were exposed to PM2.5 and PM1O.In the context of single-pollutant and two-pollutant models adjusted for NO2 or SO2,compared to their counterparts who are constantly exposed to PM2.5 at a level of 49.8?g/m3 throughout the 26th to 33th gestational weeks,the risk of delivering an infant with TLBW of pregnant women who are constantly exposed to a level of 104.0 ?g/m3 throughout these gestational weeks were 2.146(95%CI:1.434-3.210),2.194(95%CI:1.359?3.542),2.477(95%CI:1.541?3.981),respectively.In the above contexts,compared to their counterparts who are constantly exposed to PM10 at a level of 105.0?g/m3 throughout the 25th to 32th gestational weeks,the risk of delivering an infant with TLBW of pregnant women who are constantly exposed to a level of 196.1 ?g/m3 throughout these gestational weeks were 2.398(95%CI:1.425?4.035),2.573(95%CI:1.356?4.879),2.598(95%CI:1.431?4.719),respectively.5 Conclusions(1)The 26th to 33th and the 25th to 32th gestational weeks were identified as susceptible exposure windows of pregnant women who were exposed to PM2.5 and PM10,and the effect usually peaked at the 28th and 29th gestational weeks.(2)The associations between maternal PM2.5 or PM10 and TLBW observed in different models might be caused by particulates with less aerodynamic diameter,thus our results should be interpreted with caution.