Effect of air pollution on preterm birth among children born in Southern California between 1989 and 1993

We evaluated the effect of air pollution exposure during pregnancy on the occurrence of preterm birth in a cohort of 97,518 neonates born in Southern California. We used measurements of carbon monoxide (CO), nitrogen dioxide, ozone, and particulate matter less than 10 microm (PM10) collected at 17 air-quality-monitoring stations to create average exposure estimates for periods of pregnancy. We calculated crude and adjusted risk ratios (RRs) for premature birth by period-specific ambient pollution levels. We observed a 20% increase in preterm birth per 50-microg increase in ambient PM10 levels averaged over 6 weeks before birth [RRcrude = 1.20; 95% confidence interval (CI) = 1.09-1.33] and a 16% increase when averaging over the first month of pregnancy (RRcrude = 1.16; 95% CI = 1.06-1.26). PM10 effects showed no regional pattern. CO exposure 6 weeks before birth consistently exhibited an effect only for the inland regions (RRcrude = 1.13; 95% CI = 1.08-1.18 per 3 parts per million), and during the first month of pregnancy, the effect was weak for all stations (RRcrude = 1.04; 95% CI = 1.01-1.09 per 3 parts per million). Exposure to increased levels of ambient PM10 and possibly CO during pregnancy may contribute to the occurrence of preterm births in Southern California.     

A cohort study of traffic-related air pollution impacts on birth outcomes

BACKGROUND: Evidence suggests that air pollution exposure adversely affects pregnancy outcomes. Few studies have examined individual-level intraurban exposure contrasts. OBJECTIVES: We evaluated the impacts of air pollution on small for gestational age (SGA) birth weight, low full-term birth weight (LBW), and preterm birth using spatiotemporal exposure metrics. METHODS: With linked administrative data, we identified 70,249 singleton births (1999-2002) with complete covariate data (sex, ethnicity, parity, birth month and year, income, education) and maternal residential history in Vancouver, British Columbia, Canada. We estimated residential exposures by month of pregnancy using nearest and inverse-distance weighting (IDW) of study area monitors [carbon monoxide, nitrogen dioxide, nitric oxide, ozone, sulfur dioxide, and particulate matter < 2.5 (PM2.5) or < 10 (PM10) microm in aerodynamic diameter], temporally adjusted land use regression (LUR) models (NO, NO2, PM2.5, black carbon), and proximity to major roads. Using logistic regression, we estimated the risk of mean (entire pregnancy, first and last month of pregnancy, first and last 3 months) air pollution concentrations on SGA (< 10th percentile), term LBW (< 2,500 g), and preterm birth. RESULTS: Residence within 50 m of highways was associated with a 26% increase in SGA [95% confidence interval (CI), 1.07-1.49] and an 11% (95% CI, 1.01-1.23) increase in LBW. Exposure to all air pollutants except O3 was associated with SGA, with similar odds ratios (ORs) for LUR and monitoring estimates (e.g., LUR: OR = 1.02; 95% CI, 1.00-1.04; IDW: OR = 1.05; 95% CI, 1.03-1.08 per 10-microg/m3 increase in NO). For preterm births, associations were observed with PM2.5 for births < 37 weeks gestation (and for other pollutants at < 30 weeks). No consistent patterns suggested exposure windows of greater relevance. CONCLUSION: Associations between traffic-related air pollution and birth outcomes were observed in a population-based cohort with relatively low ambient air pollution exposure.     

Time-to-event analysis of fine particle air pollution and preterm birth: results from North Carolina, 2001-2005

Exposure to air pollution during pregnancy has been suggested to be a risk factor for preterm birth; however, epidemiologic evidence remains mixed and limited. The authors examined the association between ambient levels of particulate matter <2.5 μm in aerodynamic diameter (PM(2.5)) and the risk of preterm birth in North Carolina during the period 2001-2005. They estimated the risks of cumulative and lagged average exposures to PM(2.5) during pregnancy via a 2-stage discrete-time survival model. The authors also considered exposure metrics derived from 1) ambient concentrations measured by the Air Quality System (AQS) monitoring network and 2) concentrations predicted by statistically fusing AQS data with process-based numerical model output (the Statistically Fused Air and Deposition Surfaces (FSD) database). Using the AQS measurements, an interquartile-range (1.73 μg/m(3)) increase in cumulative PM(2.5) exposure was associated with a 6.8% (95% posterior interval: 0.5, 13.6) increase in the risk of preterm birth. Using the FSD-predicted levels and accounting for prediction error, the authors also found significant adverse associations between trimester 1, trimester 2, and cumulative PM(2.5) exposure and preterm birth. These findings suggest that exposure to ambient PM(2.5) during pregnancy is associated with increased risk of preterm birth, even in a region characterized by relatively good air quality.     

妊娠期PM_(2.5)暴露与新生儿低出生体重的meta分析

目的定量分析和评价妊娠期PM_(2.5)暴露对新生儿低出生体重的影响。方法通过计算机联机检索国内外文献数据库,采用meta分析对妊娠期PM_(2.5)暴露与新生儿低出生体重关系的研究进行整合分析。经异质性检验后选择合适的效应模型进行统计量的计算合并,同时检验结果的稳健性及是否存在发表偏倚。结果最终筛选出16篇文献,meta分析结果显示,整个妊娠期PM_(2.5)暴露浓度每升高10μg/m~3,新生儿发生低出生体重的风险增加9.53%(95%CI:3.92%~14.84%);妊娠早、中、后期PM_(2.5)暴露浓度每升高10μg/m~3,新生儿发生低出生体重的风险分别增加6.77%(95%CI:-4.08%~17.40%),5.83%(95%CI:-2.02%~13.98%),2.96%(95%CI:-3.05%~9.53%)。敏感性分析发现,所获得的研究结果相对稳定可靠,但在分析整个妊娠期PM_(2.5)暴露对新生儿低出生体重的影响时仍存在一定的发表偏倚。结论整个妊娠期PM_(2.5)的暴露可能增加新生儿发生低出生体重的风险。     

Moderate alcohol consumption during pregnancy and the risk of low birth weight and preterm birth. The generation R study

PURPOSE: To examine the associations of alcohol consumption in different periods of pregnancy with the risks of low birth weight and preterm birth. METHODS: This study was based on 7141 subjects participating in a population-based prospective cohort study from early pregnancy. Alcohol consumption was assessed in early, mid, and late pregnancy. Birth outcomes were birth weight in grams, low birth weight (<2500 g), small size for gestational age at birth (< -2 standard deviation scores) and preterm birth (gestational age <37 weeks). RESULTS: Overall, alcohol consumption during pregnancy was not associated with adverse birth outcomes. However, dose-response analyses showed tendencies toward adverse effects of average consumption of 1 or more alcoholic drinks per day in early pregnancy on birth weight (difference -129 g [95% confidence interval (CI): -271, 12]), low birth weight (adjusted odds ratio [aOR] 4.81 [95% CI: 1.10, 21.08]), small size for gestational age at birth (aOR 1.45 [95% CI: 0.33, 6.44]) and preterm birth (aOR 2.51 [95% CI: 0.92, 6.81]). Similar effects were found in late pregnancy. CONCLUSION: Average consumption of one or more but not less than one alcoholic drink per day in early or late pregnancy seems to be associated with adverse birth outcomes in the offspring.     

Local variations in CO and particulate air pollution and adverse birth outcomes in Los Angeles County, California, USA

We extended our previous analyses of term low birth weight (LBW) and preterm birth to 1994-2000, a period of declining air pollution levels in the South Coast Air Basin. We speculated that the effects we observed previously for carbon monoxide, particulate matter < 10 microm in aerodynamic diameter (PM10), and traffic density were attributable to toxins sorbed to primary exhaust particles. Focusing on CO, PM10, and particulate matter < 2.5 microm in aerodynamic diameter (PM2.5), we examined whether varying residential distances from monitoring stations affected risk estimates, because effect attenuation may result from local pollutant heterogeneity inadequately captured by ambient stations. We geocoded home locations, calculated the distance to the nearest air monitors, estimated exposure levels by pregnancy period, and performed logistic regression analyses for subjects living within 1-4 mi of a station. For women residing within a 1-mi distance, we observed a 27% increase in risk for high (> or = 75th percentile) first-trimester CO exposures and preterm birth and a 36% increase for high third-trimester pregnancy CO exposures and term LBW. For particles, we observed similar size effects during early and late pregnancy for both term LBW and preterm birth. In contrast, smaller or no effects were observed beyond a 1-mi distance of a residence from a station. Associations between CO and PM10 averaged over the whole pregnancy and term LBW were generally smaller than effects for early and late pregnancy. These new results for 1994-2000 generally confirm our previous observations for the period 1989-1993, again linking CO and particle exposures to term LBW and preterm birth. In addition, they confirm our suspicions about having to address local heterogeneity for these pollutants in Los Angeles.     

Fine particulate matter (PM2.5) air pollution and selected causes of postneonatal infant mortality in California

Studies suggest that airborne particulate matter (PM) may be associated with postneonatal infant mortality, particularly with respiratory causes and sudden infant death syndrome (SIDS). To further explore this issue, we examined the relationship between long-term exposure to fine PM air pollution and postneonatal infant mortality in California. We linked monitoring data for PM相似文献   

Traffic-related atmospheric pollutants levels during pregnancy and offspring's term birth weight: a study relying on a land-use regression exposure model

BACKGROUND: Some studies have suggested that particulate matter (PM) levels during pregnancy may be associated with birth weight. Road traffic is a major source of fine PM (PM with aero-dynamic diameter < 2.5 microm; PM(2.5)). OBJECTIVE: We determined to characterize the influence of maternal exposure to atmospheric pollutants due to road traffic and urban activities on offspring term birth weight. METHODS: Women from a birth cohort [the LISA (Influences of Lifestyle Related Factors on the Human Immune System and Development of Allergies in Children) cohort] who delivered a non-premature baby with a birth weight > 2,500 g in Munich metropolitan area were included. We assessed PM(2.5), PM(2.5) absorbance (which depends on the blackness of PM(2.5), a marker of traffic-related air pollution), and nitrogen dioxide levels using a land-use regression model, taking into account the type and length of roads, population density, land coverage around the home address, and temporal variations in pollution during pregnancy. Using Poisson regression, we estimated prevalence ratios (PR) of birth weight < 3,000 g, adjusted for gestational duration, sex, maternal smoking, height, weight, and education. RESULTS: Exposure was defined for 1,016 births. Taking the lowest quartile of exposure during pregnancy as a reference, the PR of birth weight < 3,000 g associated with the highest quartile was 1.7 for PM(2.5) [95% confidence interval (CI), 1.2-2.7], 1.8 for PM(2.5) absorbance (95% CI, 1.1-2.7), and 1.2 for NO(2) (95% CI, 0.7-1.7). The PR associated with an increase of 1 microg/m(3) in PM(2.5) levels was 1.13 (95% CI, 1.00-1.29). CONCLUSION: Increases in PM(2.5) levels and PM(2.5) absorbance were associated with decreases in term birth weight. Traffic-related air pollutants may have adverse effects on birth weight.     

孕前及孕期细颗粒物PM2.5对早产效应的因素分析

目的 分析细颗粒物PM2.5暴露与早产的相关性.方法 以河源市全市范围内2014年12月1日至2015年11月30日分娩的单胎活产儿和2013年12月1日至2015年11月30日河源市的细颗粒物PM2.5逐日浓度为研究对象.考虑到孕期的空气污染暴露是一个慢性的、累积的过程,并且每个产妇的孕程不同,首先以新生儿出生时的孕周为起点向后计算,将暴露时间分为4个阶段:孕前3个月,孕早期(1~13周末)、孕中期(14~27周末)和分娩前4周,分别计算PM2.5早产效应的组间差异.以某日为起点向后求和12个月的逐日暴露量作为该日分娩孕妇过去1年的PM2.5暴露总量,建立该日过去1年PM2.5累积暴露量在当日及滞后1~10d内早产例数的回归模型,并计算相对危险度.结果 河源市单胎活产儿的早产发生率为4.25%.逐日PM2.5浓度波动区间为7~108μg/m3,均值37.88μg·(m3)-1·d-1.研究对象孕前3个月、孕早期、孕中期的PM2.5合计暴露水平区间为12470~14960μg/m3,平均值为13700μg/m3.孕前3个月、孕早期、孕中期的PM2.5暴露水平在早产组与足月组间的差异无统计学意义(t值分别为2.199、2.343、0.947,均P>0.05),早产组与足月组间的PM2.5暴露水平在孕晚期的差异有统计学意义(t=4.818,P<0.05).以PM2.5累积暴露量下四分位数及其早产例数为参照(即RR=1),暴露于PM2.5累积量中位数,在滞后的10日内有意义的效应表现在滞后的第8、9、10日,RR值分别为1.49(1.01~2.21)、1.63(1.01~2.63)、1.06(1.01~1.11);暴露于PM2.5累积量中位数在滞后的10日内有意义的效应表现在滞后的第8、9、10日,RR值分别为2.05(1.02~4.15)、2.41(1.02~5.70)、1.11(1.03~1.21),累积暴露量的变化幅度与其对早产的效应呈正比,累积暴露量升高越大,在滞后期内对早产的影响也越大.结论 河源市孕期PM2.5暴露与早产有关,PM2.5暴露对早产存在非线性的滞后影响.     

Smoking during pregnancy and preterm birth according to obstetric history: French national perinatal surveys

The relation between smoking and preterm delivery is not totally known. Our aim was to determine whether smoking during pregnancy was associated with preterm birth among women at different risk according to their obstetric history. The study was based on data from the 1998 French national perinatal survey. Of the 13073 singleton live births, 4.7% were preterm; 15% of the pregnant women were moderate (one to nine cigarettes per day) and 10% heavy smokers (at least 10 cigarettes per day). Smoking heavily was related to preterm birth (crude odds ratio [OR] = 1.35, 95% confidence interval [95% CI]: [1.04, 1.74]). Multivariable logistic regression showed a relation between smoking and preterm birth among multiparae without previous adverse pregnancy outcomes; the associated adjusted ORs (AORs) were 1.25 [95% CI 0.83, 1.87] among moderate smokers and 1.46 [95% CI 0.98, 2.20] among heavy smokers. The corresponding AORs were 0.69 [95% CI 0.46, 1.05]) and 0.96 [95% CI 0.59, 1.56] for primiparae and 1.11 [95% CI 0.63, 1.93] and 0.50 [95% CI 0.25, 0.98] for multiparae with previous adverse pregnancy outcomes. Our study showed a relation between heavy smoking during pregnancy and preterm birth mostly for women with low obstetric risk.     

Physically strenuous work during pregnancy and risk of preterm birth

The aim of the study was to examine the risk of preterm birth following physically strenuous work during pregnancy. We included 343 pregnant women referred to an occupational medical clinic. Data on preterm birth and covariates were retrieved from the Danish Birth Registry. Risk estimates were computed by logistic regression using a population sample of gainfully employed women as reference (n = 345,915). The risk of preterm birth was increased in women lifting heavy loads during pregnancy (OR 1.40, 95% CI [0.88, 2.23]) but not in women with physically strenuous work (OR 0.98, 95% CI [0.66, 1.46]). The mean gestational age in the heavy-lifting group compared to the reference group was 2.4 days shorter (95% CI [0.36, 4.41]). The study challenges earlier reassuring findings as heavy-lifting pregnant women had a reduced gestational age, indicating a possibility of increased risk of preterm birth.     

Ambient air pollution and low birth weight in Connecticut and Massachusetts

BACKGROUND: Several studies have examined whether air pollution affects birth weight; however results vary and many studies were focused on Southern California or were conducted outside of the United States. OBJECTIVES: We investigated maternal exposure to particulate matter with aerodynamic diameter < 10, < 2.5 microm (PM(10), PM(2.5)), sulfur dioxide, nitrogen dioxide, and carbon monoxide and birth weight for 358,504 births in Massachusetts and Connecticut from 1999 to 2002. METHODS: Analysis included logistic models for low birth weight (< 2,500 g) and linear models with birth weight as a continuous variable. Exposure was assigned as the average county-level concentration over gestation and each trimester based on mother's residence. We adjusted for gestational length, prenatal care, type of delivery, child's sex, birth order, weather, year, and mother's race, education, marital status, age, and tobacco use. RESULTS: An interquartile increase in gestational exposure to NO(2), CO, PM(10), and PM(2.5) lowered birth weight by 8.9 g [95% confidence interval (CI), 7.0-10.8], 16.2 g (95% CI, 12.6-19.7), 8.2 g (95% CI, 5.3-11.1), and 14.7 g (95% CI, 12.3-17.1), respectively. Lower birth weight was associated with exposure in the third trimester for PM(10), the first and third trimesters for CO, the first trimester for NO(2) and SO(2), and the second and third trimesters for PM(2.5). Effect estimates for PM(2.5) were higher for infants of black mothers than those of white mothers. CONCLUSIONS: Results indicate that exposure to air pollution, even at low levels, may increase risk of low birth weight, particularly for some segments of the population.     

Adverse birth outcomes in a malarious area

To determine factors associated with fetal growth, preterm delivery and stillbirth in an area of high malaria transmission in Southern Malawi, a cross-sectional study of pregnant women attending and delivering at two study hospitals was undertaken. A total of 243 (17.3%) babies were preterm and 54 (3.7%) stillborn. Intra-uterine growth retardation (IUGR) occurred in 285 (20.3%), of whom 109 (38.2%) were low birthweight and 26 (9.1%) preterm. Factors associated with IUGR were maternal short stature [adjusted odds ratio (AOR) 1.6, 95% confidence interval (CI) 1.0-2.5]; primigravidae (AOR 1.9, 95% CI 1.4-2.7); placental or peripheral malaria at delivery (AOR 1.4, 95% CI 1.0-1.9) and maternal anaemia at recruitment (Hb<8 g/dl) (AOR 1.9, 95% CI 1.3-2.7). Increasing parasite density in the placenta was associated with both IUGR (P=0.008) and prematurity (P=0.02). Factors associated with disproportionate fetal growth were maternal malnutrition [mid-upper arm circumference (MUAC)<23 cm, AOR 1.9, 95% CI 1.0-3.7] and primigravidae (AOR 1.8, 95% CI 1.0-3.1). Preterm delivery and stillbirth were associated with <5 antenatal care visits (AOR 2.2, 95% CI 1.3-3.7 and AOR 3.1, 95% CI 1.4-7.0 respectively) and stillbirth with a positive Venereal Disease Research Laboratory (VDRL) test (AOR 4.7, 95% CI 1.5-14.8). Interventions to reduce poor pregnancy outcomes must reduce the burden of malaria in pregnancy, improve antenatal care and maternal malnutrition.     

A time-series analysis of air pollution and preterm birth in Pennsylvania, 1997-2001

Preterm delivery can lead to serious infant health outcomes, including death and lifelong disability. Small increases in preterm delivery risk in relation to spatial gradients of air pollution have been reported, but previous studies may have controlled inadequately for individual factors. Using a time-series analysis, which eliminates potential confounding by individual risk factors that do not change over short periods of time, we investigated the effect of ambient outdoor particulate matter with diameter < or = 10 microm (PM10) and sulfur dioxide on risk for preterm delivery. Daily counts of preterm births were obtained from birth records in four Pennsylvania counties from 1997 through 2001. We observed increased risk for preterm delivery with exposure to average PM10 and SO2 in the 6 weeks before birth [respectively, relative risk (RR) = 1.07; 95% confidence interval (CI), 0.98-1.18 per 50 microg/m3 increase; RR = 1.15; 95% CI, 1.00-1. 32 per 15 ppb increase], adjusting for long-term preterm delivery trends, co-pollutants, and offsetting by the number of gestations at risk. We also examined lags up to 7 days before the birth and found an acute effect of exposure to PM10 2 days and 5 days before birth (respectively, RR = 1.10; 95% CI, 1.00-1.21; RR = 1.07; 95% CI, 0.98-1.18) and SO2 3 days before birth (RR = 1.07; 95% CI, 0.99-1.15), adjusting for covariates, including temperature, dew point temperature, and day of the week. The results from this time-series analysis, which provides evidence of an increase in preterm birth risk with exposure to PM10 and SO2, are consistent with prior investigations of spatial contrasts.     

深圳市新生儿早产影响因素的病例对照研究

目的 探讨深圳市新生儿早产相关危险因素,为预防早产提供参考依据。 方法 在深圳市某妇幼保健院选取2015年1月1日－12月31日分娩的产妇和新生儿为研究对象,以妊娠满28周不足37周的200例新生儿母亲为病例组,妊娠满37周~42周的200例新生儿母亲为对照组。收集2014年1月1日－2015年12月31日SO₂、NO₂、PM₁₀、PM_2.5、CO和O₃逐日浓度。运用logistic回归模型分析早产影响因素。 结果 2014－2015年深圳市空气质量良好。病例组和对照组孕早期SO₂暴露浓度分别为(10.00±5.10)μg/m³、(8.66±5.03)μg/m³,NO₂暴露浓度分别为(38.23±15.98)μg/m³、(35.33±15.01)μg/m³,差异均有统计学意义(P＜0.05);病例组和对照组孕晚期PM₁₀暴露浓度分别为(54.26±28.00)μg/m³、(51.39±27.92)μg/m³,PM_2.5暴露浓度分别为(32.96±19.20)μg/m³、(30.11±18.36)μg/m³,差异均有统计学意义(P＜0.05)。病例组和对照组产妇年龄分别为(29.2±5.4)岁、(27.6±6.0)岁,家族早产史所占比例分别为38.5%、26.5%,大专及以上文化程度所占比例分别为62.5%、73.5%,差异均有统计学意义(P＜0.05)。进一步进行早产影响因素的多因素logistic回归分析发现:产妇年龄(OR=1.009, 95%CI:1.002~1.018)、有家族早产史(OR=1.308,95%CI:1.019~1.714)、孕晚期PM_2.5(OR=1.387,95%CI:1.112~1.579)、孕晚期PM₁₀(OR=1.267,95%CI:1.108~1.531)、孕早期SO₂(OR=1.118,95%CI:1.009~1.329)、孕早期NO₂(OR=1.106,95%CI:1.009~1.273)对早产有影响。 结论 深圳市空气SO₂、NO₂、PM₁₀、PM_2.5污染、产妇年龄和家族早产史与早产有关。     

Disparities in exposure to air pollution during pregnancy

Previous research shows poorer birth outcomes for racial and ethnic minorities and for persons with low socioeconomic status (SES). We evaluated whether mothers in groups at higher risk for poor birth outcomes live in areas of higher air pollution and whether higher exposure to air pollution contributes to poor birth outcomes. An index representing long-term exposure to criteria air pollutants was matched with birth certificate data at the county level for the United States in 1998-1999. We used linear regression to estimate associations between the air pollution index and maternal race and educational attainment, a marker for SES of the mother, controlling for age, parity, marital status, and region of the country. Then we used logistic regression models both to estimate likelihood of living in counties with the highest levels of air pollution for different racial groups and by educational attainment, adjusting for other maternal risk factors, and to estimate the effect of living in counties with higher levels of air pollution on preterm delivery and births small for gestational age (SGA). Hispanic, African-American, and Asian/Pacific Islander mothers experienced higher mean levels of air pollution and were more than twice as likely to live in the most polluted counties compared with white mothers after controlling for maternal risk factors, region, and educational status [Hispanic mothers: adjusted odds ratio (AOR) = 4.66; 95% confidence interval (95% CI), 1.92-11.32; African-American mothers: AOR = 2.58; 95% CI, 1.00-6.62; Asian/Pacific Islander mothers: AOR = 2.82; 95% CI, 1.07-7.39]. Educational attainment was not associated with living in counties with highest levels of the air pollution index (AOR = 0.95; 95% CI, 0.40-2.26) after adjusting for maternal risk factors, region of the country, and race/ethnicity. There was a small increase in the odds of preterm delivery (AOR = 1.05; 95% CI, 0.99-1.12) but not SGA (AOR = 0.96; 95% CI, 0.86-1.07) in a county with high air pollution. Additional risk of residing in areas with poor air quality may exacerbate health problems of infants and children already at increased risk for poor health.     

Traffic-related air pollution, preterm birth and term birth weight in the PIAMA birth cohort study

Background

Maternal exposure to air pollution has been associated with adverse pregnancy outcomes. Few studies took into account the spatial and temporal variation of air pollution levels.

Objectives

To evaluate the impact of maternal exposure to traffic-related air pollution during pregnancy on preterm birth and term birth weight using a spatio-temporal exposure model.

Methods

We estimated maternal residential exposure to nitrogen dioxide (NO₂), particulate matter (PM_2.5) and soot during pregnancy (entire pregnancy, 1st trimester, and last month) for 3853 singleton births within the Dutch PIAMA prospective birth cohort study by means of temporally adjusted land-use regression models. Associations between air pollution concentrations and preterm birth and term birth weight were analyzed by means of logistic and linear regression models with and without adjustment for maternal physical, lifestyle, and socio-demographic characteristics.

Results

We found positive, statistically non-significant associations between exposure to soot during entire pregnancy and during the last month of pregnancy and preterm birth [adj. OR (95% CI) per interquartile range increase in exposure 1.08 (0.88–1.34) and 1.09 (0.93–1.27), respectively]. There was no indication of an adverse effect of air pollution exposure on term birth weight.

Conclusions

In this study, maternal exposure to traffic-related air pollution during pregnancy was not associated with term birth weight. There was a tendency towards an increased risk of preterm birth with increasing air pollution exposure, but statistical power was low.     

Effects of calcium supplementation during pregnancy on maternal, fetal and birth outcomes

Gestational hypertensive disorders are the second leading cause of maternal death worldwide. Epidemiological and clinical studies have shown that an inverse relationship exists between calcium intake and development of hypertension in pregnancy. The purpose of this review was to evaluate preventive effect of calcium supplementation during pregnancy on gestational hypertensive disorders and related maternal and neonatal morbidity and mortality. A literature search was carried out on PubMed, WHOLIS, PAHO and Cochrane Library. Only randomised trials were included in the review. Data were extracted into a standardised Excel sheet. Primary outcomes were pre-eclampsia, preterm birth and birthweight. Other neonatal outcomes such as neonatal mortality, small-for-gestational age and low birthweight were also evaluated. A total of 15 randomised controlled trials were included in this review. Pooled analysis showed that calcium supplementation during pregnancy reduced risk of pre-eclampsia by 52% [relative risk (RR) 0.48; 95% confidence interval (CI) 0.34, 0.67] and that of severe pre-eclampsia by 25% (RR 0.75 [95% CI 0.57, 0.98]). There was no effect on incidence of eclampsia (RR 0.73 [95% CI 0.41, 1.27]). There was a significant reduction for risk of maternal mortality/severe morbidity (RR 0.80 [95% CI 0.65, 0.97]). Calcium supplementation during pregnancy was also associated with a significant reduction in risk of pre-term birth (RR 0.76 [95% CI 0.60, 0.97]). There was an extra gain of 85 g in the intervention group compared with control (mean difference 85 g [95% CI 37, 133]). There was no effect of calcium supplementation on perinatal mortality (RR 0.90 [95% CI 0.74, 1.09]). There was a statistically non-significant increased risk of urolithiasis in the intervention group compared with control (RR 1.52 [95% CI 0.06, 40.67]). In conclusion, calcium supplementation during pregnancy is associated with a reduction in risk of gestational hypertensive disorders and pre-term birth and an increase in birthweight. There is no increased risk of kidney stones.     

Association between gaseous ambient air pollutants and adverse pregnancy outcomes in Vancouver, Canada

The association between ambient air pollution and adverse health effects, such as emergency room visits, hospitalizations, and mortality from respiratory and cardiovascular diseases, has been studied extensively in many countries, including Canada. Recently, studies conducted in China, the Czech Republic, and the United States have related ambient air pollution to adverse pregnancy outcomes. In this study, we examined association between preterm birth, low birth weight, and intrauterine growth retardation (IUGR) among singleton live births and ambient concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone in Vancouver, Canada, for 1985-1998. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for such effects. Low birth weight was associated with exposure to SO2 during the first month of pregnancy (OR = 1.11, 95% CI, 1.01-1.22, for a 5.0 ppb increase). Preterm birth was associated with exposure to SO2 (OR = 1.09, 95% CI, 1.01-1.19, for a 5.0 ppb increase) and to CO (OR = 1.08, 95% CI, 1.01-1.15, for a 1.0 ppm increase) during the last month of pregnancy. IUGR was associated with exposure to SO2 (OR = 1.07, 95% CI, 1.01-1.13, for a 5.0 ppb increase), to NO2 (OR = 1.05, 95% CI, 1.01-1.10, for a 10.0 ppb increase), and to CO (OR = 1.06, 95% CI, 1.01-1.10, for a 1.0 ppm increase) during the first month of pregnancy. In conclusion, relatively low concentrations of gaseous air pollutants are associated with adverse effects on birth outcomes in populations experiencing diverse air pollution profiles.     

Association between Local Traffic-Generated Air Pollution and Preeclampsia and Preterm Delivery in the South Coast Air Basin of California

Background

Preeclampsia is a major complication of pregnancy that can lead to substantial maternal and perinatal morbidity, mortality, and preterm birth. Increasing evidence suggests that air pollution adversely affects pregnancy outcomes. Yet few studies have examined how local traffic-generated emissions affect preeclampsia in addition to preterm birth.

Objectives

We examined effects of residential exposure to local traffic-generated air pollution on preeclampsia and preterm delivery (PTD).

Methods

We identified 81,186 singleton birth records from four hospitals (1997–2006) in Los Angeles and Orange Counties, California (USA). We used a line-source dispersion model (CALINE4) to estimate individual exposure to local traffic-generated nitrogen oxides (NO_x) and particulate matter < 2.5 μm in aerodynamic diameter (PM_2.5) across the entire pregnancy. We used logistic regression to estimate effects of air pollution exposures on preeclampsia, PTD (gestational age < 37 weeks), moderate PTD (MPTD; gestational age < 35 weeks), and very PTD (VPTD; gestational age < 30 weeks).

Results

We observed elevated risks for preeclampsia and preterm birth from maternal exposure to local traffic-generated NO_x and PM_2.5. The risk of preeclampsia increased 33% [odds ratio (OR) = 1.33; 95% confidence interval (CI), 1.18–1.49] and 42% (OR = 1.42; 95% CI, 1.26–1.59) for the highest NO_x and PM_2.5 exposure quartiles, respectively. The risk of VPTD increased 128% (OR = 2.28; 95% CI, 2.15–2.42) and 81% (OR = 1.81; 95% CI, 1.71–1.92) for women in the highest NO_x and PM_2.5 exposure quartiles, respectively.

Conclusion

Exposure to local traffic-generated air pollution during pregnancy increases the risk of preeclampsia and preterm birth in Southern California women. These results provide further evidence that air pollution is associated with adverse reproductive outcomes.