Exposure to Fine Particulate Matter during Pregnancy and Risk of Preterm Birth among Women in New Jersey,Ohio, and Pennsylvania, 2000–2005

Background: Particulate matter ≤ 2.5 μm in aerodynamic diameter (PM_2.5) has been variably associated with preterm birth (PTB).Objective: We classified PTB into four categories (20–27, 28–31, 32–34, and 35–36 weeks completed gestation) and estimated risk differences (RDs) for each category in association with a 1-μg/m³ increase in PM_2.5 exposure during each week of gestation.Methods: We assembled a cohort of singleton pregnancies that completed ≥ 20 weeks of gestation during 2000–2005 using live birth certificate data from three states (Pennsylvania, Ohio, and New Jersey) (n = 1,940,213; 8% PTB). We estimated mean PM_2.5 exposures for each week of gestation from monitor-corrected Community Multi-Scale Air Quality modeling data. RDs were estimated using modified Poisson linear regression and adjusted for maternal race/ethnicity, marital status, education, age, and ozone.Results: RD estimates varied by exposure window and outcome period. Average PM_2.5 exposure during the fourth week of gestation was positively associated with all PTB outcomes, although magnitude varied by PTB category [e.g., for a 1-μg/m³ increase, RD = 11.8 (95% CI: –6, 29.2); RD = 46 (95% CI: 23.2, 68.9); RD = 61.1 (95% CI: 22.6, 99.7); and RD = 28.5 (95% CI: –39, 95.7) for preterm births during 20–27, 28–31, 32–34, and 35–36 weeks, respectively]. Exposures during the week of birth and the 2 weeks before birth also were positively associated with all PTB categories.Conclusions: Exposures beginning around the time of implantation and near birth appeared to be more strongly associated with PTB than exposures during other time periods. Because particulate matter exposure is ubiquitous, evidence of effects of PM_2.5 exposure on PTB, even if small in magnitude, is cause for concern.Citation: Rappazzo KM, Daniels JL, Messer LC, Poole C, Lobdell DT. 2014. Exposure to fine particulate matter during pregnancy and risk of preterm birth among women in New Jersey, Ohio, and Pennsylvania, 2000–2005. Environ Health Perspect 122:992–997; http://dx.doi.org/10.1289/ehp.1307456     

Exposure to Elemental Carbon,Organic Carbon,Nitrate, and Sulfate Fractions of Fine Particulate Matter and Risk of Preterm Birth in New Jersey,Ohio, and Pennsylvania (2000–2005)

Background

Particulate matter ≤ 2.5 μm in aerodynamic diameter (PM_2.5) has been consistently associated with preterm birth (PTB) to varying degrees, but roles of PM_2.5 species have been less studied.

Objective

We estimated risk differences (RD) of PTB (reported per 10⁶ pregnancies) associated with change in ambient concentrations of elemental carbon (EC), organic carbon (OC), nitrates (NO₃), and sulfates (SO₄).

Methods

From live birth certificates from three states, we constructed a cohort of singleton pregnancies at or beyond 20 weeks of gestation from 2000 through 2005 (n = 1,771,225; 8% PTB). We estimated mean species exposures for each week of gestation from monitor-corrected Community Multi-Scale Air Quality modeling data. RDs and 95% confidence intervals (CIs) for four PTB categories were estimated for each exposure using linear regression, adjusted for maternal race/ethnicity, marital status, education, age, smoking, maximum temperature, ozone, and season of conception. We also adjusted for other species in multi-species models.

Results

RDs varied by exposure window and outcome period. EC was positively associated with PTB after 27 and before 35 weeks of gestation. For example, for a 0.25-μg/m³ increase in EC exposure during gestational week 9, RD = 96 (95% CI: –20, 213) and RD = 145 (95% CI: –50, 341) for PTB during weeks 28–31 and 32–34, respectively. Associations with OCs were null or negative. RDs for NO₃ were elevated with exposure in early weeks of gestation, and null in later weeks. RDs for SO₄ exposure were positively associated with PTB, though magnitude varied across gestational weeks. We observed effect measure modification for associations between EC and PTB by race/ethnicity and smoking status.

Conclusion

EC and SO₄ may contribute to associations between PM_2.5 and PTB. Associations varied according to the timing of exposure and the timing of PTB.

Citation

Rappazzo KM, Daniels JL, Messer LC, Poole C, Lobdell DT. 2015. Exposure to elemental carbon, organic carbon, nitrate, and sulfate fractions of fine particulate matter and risk of preterm birth in New Jersey, Ohio, and Pennsylvania (2000–2005). Environ Health Perspect 123:1059–1065; http://dx.doi.org/10.1289/ehp.1408953     

Maternal Obesity and Risk of Preterm Birth and Low Birthweight in Hawaii PRAMS, 2000–2011

Objective Maternal obesity is a risk factor for preterm birth, a leading cause of infant morbidity and mortality. Native Hawaiian and other Pacific Islanders (NHOPI) have high rates of poor birth outcomes. Despite the high rates of obesity in NHOPI in Hawaii, the association with preterm birth has not been examined in this population. Methods We performed a retrospective cohort study of 20,061 women using data collected by Hawaii’s Pregnancy Risk Assessment Monitoring System (PRAMS) from 2000 to 2011. We investigated the contribution of maternal age, pre-pregnancy BMI, gestational diabetes, hypertension, race, socioeconomic status, and smoking to our primary outcomes of preterm birth and low birthweight using multivariable logistic regression, stratified by NHOPI versus non-NHOPI race. Results Pre-pregnancy obesity was more common in NHOPI than non-NHOPI women (23.9 and 10.5%, respectively; p?<?0.01). Overall, the risk for preterm birth increased with maternal obesity (BMI?≥?30.0; aOR?=?1.24, 95% CI 1.06–1.45, p?<?0.01), compared with normal weight women. Among NHOPI women, the prevalence of preterm birth was elevated compared with non-NHOPI women although the prevalence of low birth weight was lower. After adjusting for confounders, risk for preterm birth and low birth weight were elevated in NHOPI women compared with White women. Maternal obesity did not significantly affect the risk of prematurity within the NHOPI group. Conclusions for Practice Our study demonstrates an association between maternal pre-pregnancy obesity and preterm deliveries in Hawaii. NHOPI have high rates of pre-pregnancy obesity as well as increased risk of both preterm delivery and low birthweight when compared to White women. Further data are needed to assess interactions between race, maternal health, and neonatal morbidity, and to identify ways to improve birth outcomes for minority populations in the state of Hawaii.     

Ambient Temperature and the Risk of Preterm Birth in Guangzhou,China (2001–2011)

Background:

Although effects of weather changes on human health have been widely reported, there is limited information regarding effects on pregnant women in developing countries.

Objective:

We investigated the association between maternal exposure to ambient temperature and the risk of preterm birth (< 37 weeks of gestation) in Guangzhou, China.

Methods:

We used a Cox proportional hazards model to estimate associations between preterm birth and average temperature during each week of gestation, with weekly temperature modeled as a time-varying exposure during four time windows: 1 week (the last week of the pregnancy), 4 weeks (the last 4 weeks of the pregnancy), late pregnancy (gestational week 20 onward), and the entire pregnancy. Information on singleton vaginal birth between 2001 and 2011 was collected. Daily meteorological data during the same period were obtained from the Guangzhou Meteorological Bureau.

Results:

A total of 838,146 singleton vaginal births were included, among which 47,209 (5.6%) were preterm births. High mean temperatures during the 4 weeks, late pregnancy, and the entire pregnancy time windows were associated with an increased risk of preterm birth. Compared with the median temperature (24.4°C), weekly exposures during the last 4 weeks of the pregnancy to extreme cold (7.6°C, the 1st percentile) and extreme heat (31.9°C, the 99th percentile) were associated with 17.9% (95% CI: 10.2, 26.2%) and 10.0% (95% CI: 2.9, 17.6%) increased risks of preterm birth, respectively. The association between extreme heat and preterm birth was stronger for preterm births during weeks 20–31 and 32–34 than those during weeks 35–36.

Conclusions:

These findings might have important implications in preventing preterm birth in Guangzhou as well as other areas with similar weather conditions.

Citation:

He JR, Liu Y, Xia XY, Ma WJ, Lin HL, Kan HD, Lu JH, Feng Q, Mo WJ, Wang P, Xia HM, Qiu X, Muglia LJ. 2016. Ambient temperature and the risk of preterm birth in Guangzhou, China (2001–2011). Environ Health Perspect 124:1100–1106; http://dx.doi.org/10.1289/ehp.1509778     

Prospective Study of Ambient Particulate Matter Exposure and Risk of Pulmonary Embolism in the Nurses’ Health Study Cohort

Background

Pulmonary embolism (PE) is the most serious manifestation of venous thromboembolism and a leading cause of sudden death. Several studies have suggested associations of venous thromboembolism with short-term particulate matter (PM) exposure; evidence on long-term PM and traffic exposure is mixed.

Objectives

We examined the association of long-term exposure to PM_2.5, PM_2.5–10, and PM₁₀ (PM with diameter of ≤ 2.5, 2.5–10, and ≤ 10 μm) and distance to roadways with overall incident PE and with PE subtypes in a cohort of U.S. women.

Methods

The study included 115,745 women from the Nurses’ Health Study, followed from 1992 through 2008. Incident PE cases were self-reported biennially. Nonidiopathic PE were cases for which the medical record revealed an underlying health condition related to PE (i.e., surgery, trauma, or malignancy); idiopathic PE were cases with no such history. We used spatiotemporal models combining spatial smoothing and geographic covariates to quantify exposure at residential addresses, and Cox proportional hazards models to calculate hazard ratios (HR) and 95% confidence intervals (CIs).

Results

PM_2.5 averaged over 1 month (HR = 1.22; 95% CI: 1.04, 1.44) or 12 months (HR = 1.17; 95% CI: 0.93, 1.48) was associated with incident PE, after adjusting for known risk factors and PM_2.5–10. Equivalent analyses restricted to PE subtypes showed a positive association for PM_2.5 with nonidiopathic PE, but not with idiopathic PE. We did not find evidence of an association between distance to roadways and PE risk.

Conclusions

We provide evidence that PM in the prior 1 and 12 months is associated with PE risk. Our results also suggest that women with underlying health conditions may be more susceptible to PE after PM exposure.

Citation

Pun VC, Hart JE, Kabrhel C, Camargo CA Jr, Baccarelli AA, Laden F. 2015. Prospective study of ambient particulate matter exposure and risk of pulmonary embolism in the Nurses’ Health Study cohort. Environ Health Perspect 123:1265–1270; http://dx.doi.org/10.1289/ehp.1408927     

The Association between Maternal Oral Health Experiences and Risk of Preterm Birth in 10 States, Pregnancy Risk Assessment Monitoring System, 2004–2006

The aim of this study is to investigate the association between oral health experiences of women in the peripartum period and the risk of preterm delivery (<37?weeks). We analyzed 2004?C2006 data from the CDC Pregnancy Risk Assessment Monitoring System (PRAMS), a population-based surveillance system that collects data on pregnancy and postpartum experiences of mothers who have recently delivered a live infant. Ten states included in the analysis had a ??70% weighted response rate and three standard questions pertaining to oral health. White non-Hispanic (WNH), Black non-Hispanic (BNH), and Hispanic women were selected for analysis. Chi-squared analysis was performed for our bivariate analysis and multivariate logistic regression models were created to calculate adjusted odds ratios, controlling for socio-demographic characteristics and peripartum morbidities. Weighted percentages and standard errors were used for all analyses. Among the 35,267 women studied, in the multivariate analysis, mothers who did not receive dental care during pregnancy and did not have a teeth cleaning during pregnancy were at higher risk for delivering a preterm infant (OR 1.15, CI 1.02?C1.30; OR 1.23, CI 1.08?C1.41). In this population-based study, women who did not receive dental care or have a teeth cleaning during pregnancy were at slightly higher risk for preterm delivery after adjustment for pertinent confounders.     

A Comparison of Risk Factors for Twin Preterm Birth in the United States Between 1981–82 and 1996–97

Objective: This paper examines risk factors for twin preterm birth in 1981–82 and 1996–97 in the United States in order to see if they have changed over time. Methods: We studied all U.S. twin births for the years examined (N = 346,567). Since the gestational age distributions for twins differs from singletons, the risk of preterm birth was examined at <33, 33–34, and 35–36 weeks. Logistic regression was used to examine the contributions of sociodemographic and obstetric factors at each period. Results: While the <33 week twin preterm rate rose 7% from 1981–82 to 1996–97, the 33–34-week rate rose 31%, and the 35–36-week rate rose 51%. Women with less education, teenagers, unmarried women, primiparas, and blacks were more likely to deliver preterm across all three preterm birth levels. However, the effect of these low socioeconomic status markers diminished over the study period. Additionally, the odds of preterm birth among blacks increased with earlier gestational ages. Women who had intensive prenatal care utilization as compared with less than adequate utilization were more likely to deliver preterm (35–36 weeks) in 1996–97 (odds ratio (OR) = 2.05) compared with 1981–82 (OR = 1.44). Smaller increases were noted for <33 and 33–34 weeks. Conclusions: Obstetric factors appear to be playing a greater role in the rise of twin preterm births at 35–36 weeks gestation. Temporal sociodemographic changes do not explain the rise in the preterm rate. Changing clinical practices may be having unintended consequences on the public health goals of reducing preterm and low birthweight rates in the United States.     

Gentrification and Preterm Birth in New York City, 2008–2010

Adverse birth outcomes have been linked to neighborhood level socioeconomic status. However, little work has examined the influence of social and economic change over time (i.e., gentrification) on health. This study aims to assess the association between gentrification and preterm birth (PTB) while examining the modifying effect of maternal race/ethnicity and educational attainment. New York City births, 2008–2010, (n = 126,165) were linked to a measure of gentrification at the community district level (n = 59). The gentrification measure was calculated using percent change in education level, poverty level, and median household income (MHI) between the 2005–2009 American Community Survey and the 1990 Census. PTB was defined as clinical gestational age less than 37 weeks. Generalized estimating equations were utilized to examine the association. Gentrification (i.e., increase in residents with a college education, increase in MHI, and decrease in residents living below the poverty line) was not associated with PTB. However, among Non-Hispanic Blacks, very high gentrification was adversely associated with PTB (AOR, 1.16; 95 % CI, 1.01–1.33) as compared to those who lived in a very low gentrified neighborhood. Among non-Hispanic Whites, living in a very high gentrified neighborhood was protective as compared to living in a very low gentrified neighborhood (AOR, 0.78; 95 % CI, 0.64–0.94). Although there is a need to develop a more nuanced measure of gentrification, these results indicate that changes in the economic character of a neighborhood may have a significant influence on birth outcomes.     

Effects of Maternal Stress on Low Birth Weight and Preterm Birth Outcomes Across Neighborhoods of South Carolina, 2000–2003

Objective Studies evaluating the effect of maternal stress on preterm birth (PTB) or low birth weight (LBW) and variations across neighborhood contexts have been inconclusive. The purpose of the study was to examine the relationships among neighborhood contexts, prenatal stress, and birth outcomes, and to further explore the modifying effects of neighborhood contexts. Methods We evaluated this objective by using South Carolina Pregnancy Risk Assessment and Monitoring System (PRAMS), 2000–2003 data linked to the 2000 U.S. census data for 8064 women (N = 8064). Principal component analysis with varimax rotation was used to group stress constructs into four main domains (Financial, Emotional, Traumatic, and Spousal-related). We used multilevel logistic regression analysis to estimate the adjusted odds ratio for different models. Results Maternal stress was significantly associated with increased risks of low birth weight and preterm deliveries. Neighborhood high poverty and low education (upper quartiles) were independently associated with low birth weight but not preterm deliveries and stress appeared as a partial mediator of contextual effects on birth outcomes. The interaction models showed that the relationship between stress and LBW or PTB was modified by neighborhood contexts with risks being greater for infants born in disadvantaged neighborhoods. Conclusions Effects of maternal stress on LBW and PTB outcomes may be different for mothers living in different neighborhood contexts. Therefore, investigations that fail to examine places of residence would most likely not identify mothers at risk of LBW or PTB. Policies to improve birth outcomes need to target both places of residence and specific mediating or moderating factors associated with deprived neighborhoods of residence.     

Maternal Social Support and Neighborhood Income Inequality as Predictors of Low Birth Weight and Preterm Birth Outcome Disparities: Analysis of South Carolina Pregnancy Risk Assessment and Monitoring System Survey, 2000–2003

Effects of income inequality on health and other social systems have been a subject of considerable debate, but only a few studies have used multilevel models to evaluate these relationships. The main objectives of the study were to (1) Evaluate the relationships among neighborhood income inequality, social support and birth outcomes (low birth weight, and preterm delivery) and (2) Assess variations in racial disparities in birth outcomes across neighborhood contexts of income distribution and maternal social support. We evaluated these relationships by using South Carolina Pregnancy Risk Assessment and Monitoring System (PRAMS) survey for 2000–2003 geocoded to 2000 US Census data for South Carolina. Multilevel analysis was used to simultaneously evaluate the association between income inequality (measured as Gini), maternal social relationships and birth outcomes (low birth weight and preterm delivery). The results showed residence in neighborhoods with medium levels of income inequality was independently associated with low birth weight (OR: 2.00; 95% CI 1.14–3.26), but not preterm birth; low social support was an independent risk for low birth weight or preterm births. The evidence suggests that non-Hispanic black mothers were at increased risks of low birth weight or preterm birth primarily due to greater exposures of neighborhood deprivations associated with low income and reduced social support and modified by unequal income distribution.     

A Retrospective Assessment of Canadian Preterm Birth Prevention Efforts: 1979–1999

Objectives: To assess the achievements and effectiveness of efforts to reduce preterm deliveries through the collaborative efforts of funding agencies, scientists, obstetricians, pediatricians, and health care providers in Canada. Methods: Chronological review of studies carried out in Canada within the past two decades using several methodological approaches, including randomized clinical trials, surveys of women and physicians, and prospective cohort studies. Results: Tertiary prevention by treatment of spontaneous preterm labor with beta-agonists was effective in delaying delivery by 48 hr compared with placebo. Ongoing studies tested the comparative efficacy of oxytocin antagonists to beta-adrenergic agents. Recently, nitric oxyde donors have been tested. Secondary prevention using various approaches showed that high-risk factors could not be modified by these interventions. Before applying primary prevention approaches, surveys disclosed the lack of knowledge among both physicians and pregnant women. Conclusion: A recent Canadian consensus meeting emphasized the potential for success by using multidisciplinary, community-based health promotion approaches to prevent preterm labor; enhancing basic research in predictive markers such as cervical change, infection/inflammation, and psychosocial stress; and increasing political involvement of health decision makers.     

Contribution of Maternal Age to Preterm Birth Rates in Denmark and Quebec, 1981–2008

Objectives. We sought evidence to support the hypothesis that advancing maternal age is potentially causing a rise in preterm birth (PTB) rates in high-income countries.Methods. We assessed maternal age-specific trends in PTB using all singleton live births in Denmark (n = 1 674 308) and Quebec (n = 2 291 253) from 1981 to 2008. We decomposed the country-specific contributions of age-specific PTB rates and maternal age distribution to overall PTB rates over time.Results. PTB rates increased from 4.4% to 5.0% in Denmark and from 5.1% to 6.0% in Quebec. Rates increased the most in women aged 20 to 29 years, whereas rates decreased or remained stable in women aged 35 years and older. The overall increase over time was driven by age-specific PTB rates, although the contribution of younger women was countered by fewer births at this age in both Denmark and Quebec.Conclusions. PTB rates increased among women aged 20 to 29 years, but their contribution to the overall PTB rates was offset by older maternal age over time. Women aged 20 to 29 years should be targeted to reduce PTB rates, as potential for prevention may be greater in this age group.Preterm birth (PTB) rates are rising in many high-income countries,1–5 but international comparisons that seek to understand the underlying reasons for the increase are lacking. It has been proposed that the rise in PTB is partly attributable to an increase in maternal age,6 as women in Western countries increasingly delay pregnancy to later in life.7–9 Several studies have shown strong associations between advanced maternal age and PTB,10–12 but other studies only adjust for this variable,13,14 making it difficult to determine the extent to which changes in maternal age are in fact responsible for the increase in PTB rates over time. The United States is the only country that has assessed the contribution of maternal age to changes in PTB rates, but older maternal age accounted for only a small portion of the increase,1,15 a finding at odds with the notion that older age is driving the increase.Birth rates at advanced maternal ages, however, tend to be much lower in the United States than in other high-income countries.16 A better understanding of how maternal age-specific PTB rates contribute to trends in overall PTB rates in other countries could help provide international goals for the reduction of PTB. PTB is major cause of infant morbidity and mortality,2,17 with significant impact on health and development throughout life18,19 and considerable economic costs to society.1 Thus, the importance of assessing demographic contributions of population distribution to worldwide trends in PTB is easily justifiable. As a first step in achieving this goal, we sought to determine the contribution of older maternal to PTB rates over time in Denmark and Canada, 2 high-income areas characterized by advancing maternal age and rising PTB rates.8,20 These countries are similar in respect to universal access to care but differ regarding maternal age distribution and age-specific PTB rates.     

Association Between Maternal Multivitamin Use and Preterm Birth in 24 States,Pregnancy Risk Assessment Monitoring System, 2009–2010

Objectives The study objective was to examine the prevalence of maternal multivitamin use and associations with preterm birth (<37 weeks gestation) in the United States. We additionally examined whether associations differed by race/ethnicity. Methods Using the Pregnancy Risk Assessment Monitoring System, we analyzed 2009–2010 data among women aged ≥18 years with a singleton live birth who completed questions on multivitamin use 1 month prior to pregnancy (24 states; n = 57,348) or in the last 3 months of pregnancy (3 states, n = 5095). Results In the month prior to pregnancy, multivitamin use ≥4 times/week continued to remain low (36.8 %). In the last 3 months of pregnancy, 79.6 % of women reported using multivitamins ≥4 times/week. Adjusting for confounders, multivitamin use 1–3 times/week or ≥4 times/week prior to pregnancy was not associated with preterm birth overall. Though there was no evidence of dose response, any multivitamin use in the last 3 months of pregnancy was associated with a significant reduction in preterm birth among non-Hispanic black women. Conclusions for Practice Multivitamin use during pregnancy may help reduce preterm birth, particularly among populations with the highest burden, though further investigations are warranted.     

Father’s Education: An Independent Marker of Risk for Preterm Birth

To explore the association between paternal education and preterm birth, taking into account maternal social and economic factors. We analyzed data from a population-based cross-sectional postpartum survey, linked with birth certificates, of women who gave birth in California from 1999 through 2005 (n = 21,712). Women whose infants’ fathers had not completed college had significantly higher odds of preterm birth than women whose infants’ fathers were college graduates, even after adjusting for maternal education and family income [OR (95% CI) = 1.26 (1.01–1.58)]. The effect of paternal education was greater among unmarried women than among married women. Paternal education may represent an important indicator of risk for preterm birth, reflecting social and/or economic factors not measured by maternal education or family income. Researchers and policy makers committed to understanding and reducing socioeconomic disparities in birth outcomes should consider paternal as well as maternal socioeconomic factors in their analyses and policy decisions.     

Socioeconomic Status and Foodborne Pathogens in Connecticut,USA, 2000–2011

Foodborne pathogens cause >9 million illnesses annually. Food safety efforts address the entire food chain, but an essential strategy for preventing foodborne disease is educating consumers and food preparers. To better understand the epidemiology of foodborne disease and to direct prevention efforts, we examined incidence of Salmonella infection, Shiga toxin–producing Escherichia coli infection, and hemolytic uremic syndrome by census tract–level socioeconomic status (SES) in the Connecticut Foodborne Diseases Active Surveillance Network site for 2000–2011. Addresses of case-patients were geocoded to census tracts and linked to census tract–level SES data. Higher census tract–level SES was associated with Shiga toxin–producing Escherichia coli, regardless of serotype; hemolytic uremic syndrome; salmonellosis in persons ≥5 years of age; and some Salmonella serotypes. A reverse association was found for salmonellosis in children <5 years of age and for 1 Salmonella serotype. These findings will inform education and prevention efforts as well as further research.     

Chronic Fine and Coarse Particulate Exposure,Mortality, and Coronary Heart Disease in the Nurses’ Health Study

Background

The relationship of fine particulate matter < 2.5 μm in diameter (PM_2.5) air pollution with mortality and cardiovascular disease is well established, with more recent long-term studies reporting larger effect sizes than earlier long-term studies. Some studies have suggested the coarse fraction, particles between 2.5 and 10 μm (PM_10–2.5), may also be important. With respect to mortality and cardiovascular events, questions remain regarding the relative strength of effect sizes for chronic exposure to fine and coarse particles.

Objectives

We examined the relationship of chronic PM_2.5 and PM_10–2.5 exposures with all-cause mortality and fatal and nonfatal incident coronary heart disease (CHD), adjusting for time-varying covariates.

Methods

The current study included women from the Nurses’ Health Study living in metropolitan areas of the northeastern and midwestern United States. Follow-up was from 1992 to 2002. We used geographic information systems–based spatial smoothing models to estimate monthly exposures at each participant’s residence.

Results

We found increased risk of all-cause mortality [hazard ratio (HR), 1.26; 95% confidence interval (CI), 1.02–1.54] and fatal CHD (HR = 2.02; 95% CI, 1.07–3.78) associated with each 10-μg/m³ increase in annual PM_2.5 exposure. The association between fatal CHD and PM_10–2.5 was weaker.

Conclusions

Our findings contribute to growing evidence that chronic PM_2.5 exposure is associated with risk of all-cause and cardiovascular mortality.     

Dental Cleaning,Community Water Fluoridation and Preterm Birth,Massachusetts: 2009–2016

Maternal and Child Health Journal - Objectives Data on the potential effect of dental cleaning and community water fluoridation (CWF) on pregnancy outcomes are scarce. While numerous studies...     

A Case–Control Study of Prenatal Thallium Exposure and Low Birth Weight in China

Background

Thallium (Tl) is a highly toxic heavy metal widely present in the environment. Case reports have suggested that maternal exposure to high levels of Tl during pregnancy is associated with low birth weight (LBW), but epidemiological data are limited.

Objectives

This study was designed to evaluate whether prenatal Tl exposure is associated with an increased risk of LBW.

Methods

This case–control study involving 816 study participants (204 LBW cases and 612 matched controls) was conducted in Hubei Province, China, in 2012–2014. Tl concentrations were measured in maternal urine collected at delivery, and associations with LBW were evaluated using conditional logistic regression.

Results

Higher maternal urinary Tl levels were significantly associated with increased risk of LBW [crude odds ratio (OR) = 1.52; 95% CI: 1.00, 2.30 for the highest vs. lowest tertile], and the association was similarly elevated after adjustment for potential confounders (adjusted OR = 1.90; 95% CI: 1.01, 3.58 for the highest vs. lowest tertile). Stratified analyses showed slightly higher risk estimates for LBW associated with higher Tl levels for mothers < 28 years old and for mothers with lower household income; however, there was no statistical evidence of heterogeneity in risk according to maternal age (p for heterogeneity = 0.18) or household income (p for heterogeneity = 0.28).

Conclusion

To our knowledge, ours is the first case–control study to investigate the association between prenatal Tl exposure and LBW. The results suggest that prenatal exposure to high levels of Tl may be associated with an increased risk of LBW.

Citation

Xia W, Du X, Zheng T, Zhang B, Li Y, Bassig BA, Zhou A, Wang Y, Xiong C, Li Z, Yao Y, Hu J, Zhou Y, Liu J, Xue W, Ma Y, Pan X, Peng Y, Xu S. 2016. A case–control study of prenatal thallium exposure and low birth weight in China. Environ Health Perspect 124:164–169; http://dx.doi.org/10.1289/ehp.1409202