Maternal asthma in relation to infant size and body composition.

Background: Asthma affects 10% of pregnancies and may influence offspring health, including infant size and body composition, through hypoxic and inflammatory pathways. Objective: We sought to determine associations between maternal asthma and asthma phenotypes during pregnancy and infant size and body composition. Methods: The B-WELL-Mom study (2015-19) is a prospective cohort of 418 pregnant persons with and without asthma recruited in the first trimester of pregnancy from 2 US obstetric clinics. Exposures were maternal self-reported active asthma (n = 311) or no asthma (n = 107), and asthma phenotypes were classified on the bases of atopy, onset, exercise induced, control, severity, symptomology, and exacerbations. Outcomes were infant weight, length, head circumference, and skinfold measurements at birth and postnatal follow-up, as well as fat and lean mass assessed by air displacement plethysmography at birth. Adjusted multivariable linear regression examined associations of maternal asthma and asthma phenotypes with infant outcomes. Results: Offspring were born at a mean ± SD of 38 ± 2.3 weeks' gestation and were 18 ± 2.2 weeks of age at postnatal follow-up. Infants of participants with asthma had a mean ± SD fat mass of 11.0 ± 4.2%, birth weight of 3045.8 ± 604.3 g, and postnatal follow-up weight of 6696.4 ± 964.2 g, which were not different from infants of participants without asthma (respectively, ß [95% confidence interval]: -0.1 [-1.4, 1.3], -26.7 [-156.9, 103.4], and 107.5 [-117.3, 332.3]). Few associations were observed between asthma or asthma phenotypes and infant size or body composition. Conclusions: In a current obstetric cohort, maternal asthma during pregnancy was not associated with differential infant size or body composition.

TikTok and YouTube Videos on Overactive Bladder Exhibit Poor Quality and Diversity.

INTRODUCTION: We sought to assess the quality, understandability, actionability, and diversity of speakers in videos on TikTok and YouTube regarding overactive bladder. METHODS: Using Application Program Interface, the top 500 TikTok and 120 YouTube videos on overactive bladder were retrieved. Videos unrelated to overactive bladder, those not in English, longer than 10 minutes, or lacking both text and audio were excluded. Surgical technique videos for providers were also excluded. Videos were scored by trained raters using 2 validated instruments: PEMAT (Agency for Healthcare Research and Quality's Patient Education Materials Assessment Tool) for actionability and understandability, and the DISCERN instrument for quality of consumer health information. We also examined for evidence of misinformation and commercial bias. RESULTS: One hundred thirty-six TikTok videos and 75 YouTube videos met inclusion criteria. Eighty-eight percent of TikTok videos had poor PEMAT actionability scores (a score below 75%), as compared to 60% of YouTube videos. Both YouTube and TikTok videos scored low on PEMAT understandability. Ninety-eight percent of TikTok videos and 65% of YouTube videos were poor quality (DISCERN score <3). YouTube videos had higher actionability and quality than TikTok videos (P < .001) but did not differ on understandability (P = .769). Twenty-three percent of TikTok and 11% of YouTube videos had high misinformation (score >3). Commercial bias was present in 10% of TikTok and 19% of YouTube videos. CONCLUSIONS: Actionability, understandability, and quality for overactive bladder-related content is poor on YouTube and TikTok. With increasing access to social media, it is important that health care providers and organizations invest resources in patient education on health literacy.

Asthma Medication Regimens in Pregnancy: Longitudinal Changes in Asthma Status.

OBJECTIVE: This study aimed to assess the impact of common asthma medication regimens on asthma symptoms, exacerbations, lung function, and inflammation during pregnancy. STUDY DESIGN: A total of 311 women with asthma were enrolled in a prospective pregnancy cohort. Asthma medication regimen was categorized into short-acting ß agonist (SABA) alone, SABA + inhaled corticosteroid (ICS), SABA + ICS + long-acting ß agonist (LABA), and no asthma medications (reference). We evaluated asthma control at enrollment (< 15 weeks' gestation) and its change into trimesters 2 and 3, including per cent predicted forced expiratory volume in 1 second (%FEV1) and peak expiratory flow (%PEF), pulse oximetry, fractional exhaled nitric oxide (FeNO), asthma symptoms (asthma attacks/month, night symptoms/week), and severe exacerbations. Linear mixed models adjusted for site, age, race, annual income, gestational age, body mass index, and smoking, and propensity scores accounted for asthma control status at baseline. RESULTS: Women taking SABA + ICS and SABA + ICS + LABA had better first trimester %PEF (83.5% [75.7-91.3] and 84.6% [76.9-92.3], respectively) compared with women taking no asthma medications (72.7% [66.0-79.3]). Women taking SABA + ICS + LABA also experienced improvements in %FEV1 (+11.1%, p < 0.01) in the third trimester and FeNO in the second (-12.3 parts per billion [ppb], p < 0.01) and third (-11.0 ppb, p < 0.01) trimesters as compared with the trajectory of women taking no medications. SABA + ICS use was associated with increased odds of severe exacerbations in the first (odds ratio [OR]: 2.22 [1.10-4.46]) and second (OR: 3.15 [1.11-8.96]) trimesters, and SABA + ICS + LABA use in the second trimester (OR: 7.89 [2.75-21.47]). Women taking SABA alone were similar to those taking no medication. CONCLUSION: Pregnant women taking SABA + ICS and SABA + ICS + LABA had better lung function in the first trimester. SABA + ICS + LABA was associated with improvements in lung function and inflammation across gestation. However, both the SABA + ICS and SABA + ICS + LABA groups had a higher risk of severe exacerbation during early to mid-pregnancy. KEY POINTS: · Medication regimens may affect perinatal asthma control.. · Intensive regimens improved lung function/inflammation.. · Women on intensive regimens had more acute asthma events..

Maternal body composition and gestational weight gain in relation to asthma control during pregnancy.

BACKGROUND: Poor asthma control is common during pregnancy and contributes to adverse pregnancy outcomes. Identification of risk factors for poor gestational asthma control is crucial. OBJECTIVE: Examine associations of body composition and gestational weight gain with asthma control in a prospective pregnancy cohort (n = 299). METHODS: Exposures included pre-pregnancy body mass index (BMI), first trimester skinfolds, and trimester-specific gestational weight gain. Outcomes included percent predicted forced expiratory volumes (FEV1, FEV6), forced vital capacity (FVC), peak expiratory flow (PEF), FEV1/FVC, symptoms (activity limitation, nighttime symptoms, inhaler use, and respiratory symptoms), and exacerbations (asthma attacks, medical encounters). Linear and Poisson models examined associations with lung function (ß (95% confidence interval (CI)), asthma symptom burden (relative rate ratio (RR (95%CI)), and exacerbations (RR (95%CI)). RESULTS: Women with a BMI ≥ 30 had lower percent predicted FVC across pregnancy (ßThirdTrimester: -5.20 (-8.61, -1.78)) and more frequent night symptoms in the first trimester (RR: 1.66 (1.08, 2.56)). Higher first trimester skinfolds were associated with lower FEV1, FEV6, and FVC, and more frequent night symptoms and inhaler use across pregnancy. Excessive first trimester gestational weight gain was associated with more frequent activity limitation in the first trimester (RR: 3.36 (1.15, 9.80)) and inhaler use across pregnancy (RRThirdTrimester: 3.49 (1.21, 10.02)). CONCLUSIONS: Higher adiposity and first trimester excessive gestational weight gain were associated with restrictive changes in lung function and symptomology during pregnancy.

Joint effects of ethnic enclave residence and ambient volatile organic compounds exposure on risk of gestational diabetes mellitus among Asian/Pacific Islander women in the United States.

BACKGROUND: Asian/Pacific Islander (API) communities in the United States often reside in metropolitan areas with distinct social and environmental attributes. Residence in an ethnic enclave, a socially distinct area, is associated with lower gestational diabetes mellitus (GDM) risk, yet exposure to high levels of air pollution, including volatile organic compounds (VOCS), is associated with increased GDM risk. We examined the joint effects of ethnic enclaves and VOCs to better understand GDM risk among API women, the group with the highest prevalence of GDM. METHODS: We examined 9069 API births in the Consortium on Safe Labor (19 hospitals, 2002-2008). API ethnic enclaves were defined as areas ≥66th percentile for percent API residents, dissimilarity (geographic dispersal of API and White residents), and isolation (degree that API individuals interact with another API individual). High levels of 14 volatile organic compounds (VOC) were defined as ≥75th percentile. Four joint categories were created for each VOC: Low VOC/Enclave (reference group), Low VOC/No Enclave, High VOC/Enclave, High VOC/No Enclave. GDM was reported in medical records. Hierarchical logistic regression estimated odds ratios (OR) and 95% confidence intervals (95%CI) between joint exposures and GDM, adjusted for maternal factors and area-level poverty. Risk was estimated for 3-months preconception and first trimester exposures. RESULTS: Enclave residence was associated with lower GDM risk regardless of VOC exposure. Preconception benzene exposure was associated with increased risk when women resided outside enclaves [High VOC/No Enclave (OR:3.45, 95%CI:1.77,6.72)], and the effect was somewhat mitigated within enclaves, [High VOC/Enclave (OR:2.07, 95%:1.09,3.94)]. Risks were similar for 12 of 14 VOCs during preconception and 10 of 14 during the first trimester. CONCLUSIONS: API residence in non-enclave areas is associated with higher GDM risk, regardless of VOC level. Ethnic enclave residence may mitigate effects of VOC exposure, perhaps due to lower stress levels. The potential benefit of ethnic enclaves warrants further study.

Air pollution exposure and risk of adverse obstetric and neonatal outcomes among women with type 1 diabetes.

AIMS/HYPOTHESIS: Women with type 1 diabetes have increased risk for poor obstetric outcomes. Prenatal air pollution exposure is also associated with adverse outcomes for women and infants. We examined whether women with type 1 diabetes are more vulnerable than other women to pollution-associated risks during pregnancy. METHODS: In singleton deliveries from the Consortium on Safe Labor (2002-2008), obstetric and neonatal outcomes were compared for women with type 1 diabetes (n = 507) and women without autoimmune disease (n = 204,384). Preconception, trimester, and whole pregnancy average air pollutant exposure (ozone (O3), carbon monoxide (CO), particulate matter >10 µm (PM10), PM > 2.5 µm (PM2.5), sulfur dioxide (SO2), nitrogen oxides (NOx)) were estimated using modified Community Multiscale Air Quality models. Poisson regression models with diabetes*pollutant interaction terms estimated relative risks and 95% confidence intervals for adverse outcomes, adjusted for maternal characteristics and geographic region. RESULTS: For whole pregnancy exposure to SO2, women with type 1 diabetes had 15% increased risk (RR:1.15 95%CI:1.01,1.31) and women without autoimmune disease had 5% increased risk (RR:1.05 95%CI:1.05,1.06) for small for gestational age birth (pinteraction = 0.09). Additionally, whole pregnancy O3 exposure was associated with 10% increased risk (RR:1.10 95%CI:1.02,1.17) among women with type 1 diabetes and 2% increased risk (RR:1.02 95%CI:1.00,1.04) among women without autoimmune disease for perinatal mortality (pinteraction = 0.08). Similar patterns were observed between PM2.5 exposure and spontaneous preterm birth. CONCLUSIONS: Pregnant women with type 1 diabetes may be at greater risk for adverse outcomes when exposed to air pollution than women without autoimmune disease.

Chronic exposure to air pollution and risk of mental health disorders complicating pregnancy.

BACKGROUND: Air pollution is associated with mental health in the general population, but its influence on maternal mental health during pregnancy has not been assessed. OBJECTIVE: We evaluated the relationship between unspecified mental disorders complicating pregnancy and depression with average air pollution exposure during 3-months preconception, first trimester and whole pregnancy. METHODS: Ambient air pollution was derived from a modified Community Multiscale Air Quality model and mental health diagnoses were based on electronic intrapartum medical records. Logistic regression models assessed the odds of unspecified mental disorder complicating pregnancy (n = 11,577) and depression (n = 9793) associated with an interquartile range increase in particulate matter (PM) less than 2.5 µm (PM2.5), PM10, carbon monoxide (CO), nitrogen dioxide (NO2), nitrogen oxide (NOx), sulfur dioxide (SO2), and ozone (O3). Pregnancies without mental health disorders were the reference group (n = 211,645). Models were adjusted for maternal characteristics and study site; analyses were repeated using cases with no additional mental health co-morbidity. RESULTS: Whole pregnancy exposure to PM10, PM2.5, NO2, and NOx was associated with a 29%-74% increased odds of unspecified mental disorders complicating pregnancy while CO was associated with 31% decreased odds. Results were similar for depression: whole pregnancy exposure to PM10, PM2.5, NO2, and NOx was associated with 11%-21% increased odds and CO and O3 were associated with 16%-20% decreased odds. SO2 results were inconsistent, with increased odds for unspecified mental disorders complicating pregnancy and decreased odds for depression. While most findings were similar or stronger among cases with no co-morbidity, PM2.5 and NOx were associated with reduced risk and SO2 with increased risk for depression only. DISCUSSION: Whole pregnancy exposure to PM10, PM2.5, NO2, and NOx were associated with unspecified mental disorder complicating pregnancy and depression, but some results varied for depression only. These risks merit further investigation.

Does maternal race or ethnicity modify the association between maternal psychiatric disorders and preterm birth?

PURPOSE: Preterm birth risk has been linked to maternal racial and ethnic background, particularly African American heritage; however, the association of maternal race and ethnicity with psychiatric disorders and preterm birth has received relatively limited attention. METHODS: The Consortium on Safe Labor (2002-2008) is a nationwide U.S. cohort study with 223,394 singleton pregnancies. Clinical data were obtained from electronic medical records, including maternal diagnoses of psychiatric disorders. Relative risk (RR) and 95% confidence intervals (CI) were estimated for the association between maternal psychiatric disorders and preterm birth (<37 completed weeks) using log-binomial regression with generalized estimating equations. The interaction effect of maternal psychiatric disorders with race and ethnicity was also evaluated. RESULTS: Non-Hispanic White (RR, 1.42; 95% CI, 1.35-1.49), Hispanic (RR, 1.44; 95% CI, 1.29-1.60), and non-Hispanic Black (RR, 1.21, 95% CI, 1.13-1.29) women with any psychiatric disorder were at increased risk for delivering preterm infants, compared with women without any psychiatric disorder. However, non-Hispanic Black women with any psychiatric disorder, depression, bipolar disorder, and schizophrenia had a significantly lower increase in preterm birth risk than non-Hispanic White women. CONCLUSIONS: Despite the significant association between maternal psychiatric disorders and preterm birth risk, psychiatric disorders did not appear to contribute to racial and ethnic disparities in preterm birth.

Gestational and Postpartum Weight Trajectories Among Women With and Without Asthma.

Asthma leads to increased weight gain in nonpregnant populations, but studies have not examined this association within the context of pregnancy. The association between asthma and perinatal weight trajectories was examined in the Breathe-Wellbeing, Environment, Lifestyle, and Lung Function Study (2015-2019). Multilevel linear spline models were adjusted for age, race/ethnicity, income, marital status, education, cigarette smoking, parity, study site, and prepregnancy body mass index were used to examine differences in perinatal weight trajectories between women with (n = 299) and without (n = 101) asthma. Secondary analyses were conducted to assess whether associations differed by asthma phenotypes. At 40 weeks' gestation, women with asthma gained 16.2 kg (95% confidence interval (CI): 14.6, 17.7) and women without asthma gained 13.1 kg (95% CI: 10.9, 15.4). At 3 months postpartum, women with asthma retained 10.4 kg (95% CI: 8.9, 11.9) and women without asthma retained 8.0 kg (95% CI: 5.9, 10.2). Among women with asthma, exercise-induced asthma and step 3 asthma medications were associated with excess gestational weight gain. These study findings suggest women with asthma gain and retain more weight during pregnancy and postpartum than do women without asthma.

Ambient temperature and stillbirth: Risks associated with chronic extreme temperature and acute temperature change.

BACKGROUND: Ambient temperature events are increasing in frequency and intensity. Our prior work in a U.S. nationwide study suggests a strong association between both chronic and acute temperature extremes and stillbirth risk. OBJECTIVE: We attempted to replicate our prior study by assessing stillbirth risk associated with average whole-pregnancy temperatures and acute ambient temperature changes in a low-risk U.S. METHODS: Singleton deliveries in the NICHD Consecutive Pregnancies Study (Utah, 2002-2010; n = 112,005) were identified using electronic medical records. Ambient temperature was derived from the Weather Research and Forecasting model. Binary logistic regression determined the adjusted odds ratio (aOR) and 95% confidence interval (95% CI) for stillbirth associated with whole-pregnancy exposure to extreme cold (<10th percentile) and hot (>90th percentile) versus moderate (10th-90th percentiles) average temperature, adjusting for maternal demographics, season of conception, hypertensive disorders of pregnancy, and gestational diabetes. In a case-crossover analysis, we estimated the stillbirth aOR and 95% CI for each 1° Celsius increase during the week prior to delivery using conditional logistic regression. In both models, we adjusted for relative humidity, ozone, and fine particulates. RESULTS: We observed 500 stillbirth cases among 498 mothers. Compared to moderate temperatures, whole-pregnancy exposure to extreme cold (aOR: 4.42, 95% CI:3.43, 5.69) and hot (aOR: 5.06, 95% CI: 3.34, 7.68) temperatures were associated with stillbirth risk. Case-crossover models observed a 7% increased odds (95% CI: 1.04, 1.10) associated with each 1° Celsius increase during the week prior to delivery. DISCUSSION: Both chronic and acute ambient temperature were associated with odds of stillbirth in this low-risk population, similar to our prior nationwide findings. Future increases in temperature extremes are likely and the observed risk in a low-risk population suggests this association merits attention.

Air Pollution Exposure Monitoring among Pregnant Women with and without Asthma.

Background: We monitored exposure to fine particulates (PM2.5), ozone, nitrogen dioxide (NO2), and ambient temperature for pregnant women with and without asthma. Methods: Women (n = 40) from the Breathe-Well-Being, Environment, Lifestyle, and Lung Function Study (2015-2018) were enrolled during pregnancy and monitored for 2-4 days. Daily pollutants were measured using personal air monitors, indoor air monitors, and nearest Environmental Protection Agency's stationary monitors based on GPS tracking and home address. Results: Personal-monitor measurements of PM2.5, ozone, and NO2 did not vary by asthma status but exposure profiles significantly differed by assessment methods. EPA stationary monitor-based methods appeared to underestimate PM2.5 and temperature exposure and overestimate ozone and NO2 exposure. Higher indoor-monitored PM2.5 exposures were associated with smoking and the use of gas appliances. The proportion of waking-time during which personal monitors were worn was ~56%. Lower compliance was associated with exercise, smoking, being around a smoker, and the use of a prescription drug. Conclusions: Exposure did not vary by asthma status but was influenced by daily activities and assessment methods. Personal monitors may better capture exposures but non-compliance merits attention. Meanwhile, larger monitoring studies are warranted to further understand exposure profiles and the health effects of air pollution during pregnancy.

Association of Maternal Exposure to Persistent Organic Pollutants in Early Pregnancy With Fetal Growth.

Importance: Prenatal exposure to persistent organic pollutants (POPs) has been associated with birth size, but data on fetal growth and among racially/ethnically diverse pregnant women remain scarce. Objectives: To assess the association between maternal plasma POPs in early pregnancy and fetal growth and by infant sex and maternal race/ethnicity. Design, Setting, and Participants: This cohort study used the National Institute of Child Health and Human Development Fetal Growth Studies-Singleton cohort, which recruited nonobese, low-risk pregnant women before 14 weeks' gestation between July 1, 2009, and January 31, 2013, in 12 community-based clinics throughout the United States. Participants self-identified their race/ethnicity, self-reported their behavioral risk factors, and were followed up throughout their pregnancy. Data were analyzed from July 31, 2018, to June 3, 2019. Exposures: Levels of 76 POPs in early gestation plasma were measured: 11 perfluoroalkyl and polyfluoroalkyl substances, 1 polybrominated biphenyl, 9 polybrominated diphenyl ethers (PBDEs), 44 polychlorinated biphenyls (PCBs), and 11 organochlorine pesticides (OCPs). The bayesian kernel machine regression method was used to examine chemical class mixtures, and generalized additive mixed model was used to analyze individual chemicals. Main Outcomes and Measures: Fourteen fetal biometrics were measured, including head circumference, abdominal circumference, and femur length, within 5 ultrasonography appointments. Results: A total of 2284 low-risk pregnant women were included: 606 women (26.5%) self-identified as white with a mean (SD) age of 30.3 (4.4) years, 589 (25.8%) as black with a mean (SD) age of 25.5 (5.5) years, 635 (27.8%) as Hispanic with a mean (SD) age of 27.1 (5.5) years, and 454 (19.9%) as Asian with a mean (SD) age of 30.5 (4.5) years. A comparison between the 75th and 25th percentile of exposure revealed that the OCP mixture was negatively associated with most fetal growth measures, with a reduction of 4.7 mm (95% CI, -6.7 to -2.8 mm) in head circumference, 3.5 mm (95% CI, -4.7 to -2.2 mm) in abdominal circumference, and 0.6 mm (95% CI, -1.1 to -0.2 mm) in femur length. Higher exposure to the PBDE mixture was associated with reduced abdominal circumference (-2.4 mm; 95% CI, -4.0 to -0.5 mm) and femur length (-0.5 mm; 95% CI, -1.0 to -0.1 mm), and the dioxin-like PCB mixture was associated with reduced head circumference (-6.4 mm; 95% CI, -8.4 to -4.3 mm) and abdominal circumference (-2.4 mm; 95% CI, -3.9 to -0.8 mm). Associations with individual chemicals were less consistent. There were some interactions by fetal sex, although most of the results did not vary by maternal race/ethnicity. For example, oxychlordane (-0.98 mm; 95% CI, -1.60 to -0.36 mm; P for interaction <.001), trans-nonachlor (-0.31 mm; 95% CI, -0.54 to -0.08 mm; P for interaction = .005), and p,p'-dichlorodiphenyldichloroethylene (-0.19 mm; 95% CI, -0.22 to -0.09 mm; P for interaction = .006) were associated with shorter femur length among boys only. Conclusions and Relevance: This study found that, among pregnant women with low POP levels, a mixture of OCPs was negatively associated with most fetal growth measures and that mixtures of PBDEs and dioxin-like PCBs were associated with reduced abdominal circumference. These findings suggested that, although exposures may be low, associations with fetal growth are apparent.

Ethnic Enclaves and Pregnancy and Behavior Outcomes Among Asian/Pacific Islanders in the USA.

OBJECTIVES: Ethnic enclaves are ethnically, spatially, and socially distinct communities that may promote health through access to culturally appropriate resources and reduced exposure to discrimination. This study examined ethnic enclave residence and pregnancy outcomes among Asian/Pacific Islander (API) women in the USA. DESIGN: We examined 9206 API births in the Consortium on Safe Labor (2002-2008). Ethnic enclaves were defined as hospital regions with high percentage of API residents (> 4%), high dissimilarity index (> 0.41; distribution of API and white residents within a geographic area), and high isolation index (> 0.03; interaction between API and white residents in an area). Gestational diabetes mellitus (GDM), preterm birth (PTB), small for gestational age (SGA), and smoking and alcohol use during pregnancy were reported in medical records supplemented with ICD-9 codes. Hierarchical logistic regression models estimated associations between ethnic enclaves and pregnancy outcomes, adjusted for maternal factors, area-level poverty, and air pollution. RESULTS: Women in enclaves had lower odds of GDM (OR 0.61; 95%CI 0.45, 0.82), PTB (OR 0.74; 95%CI 0.56, 0.99), and SGA (OR 0.68; 95%CI 0.52, 0.89) compared with women in non-enclaves. Prenatal smoking and alcohol use appeared less likely in enclaves, but estimates were imprecise. Within enclaves, about 10.5% of homes speak an API language, compared with 6.0% in non-enclaves. The mean percent of foreign-born API populations was 67.4% in enclaves and 68.8% in non-enclaves. CONCLUSIONS: API women residing in ethnic enclaves had better pregnancy outcomes than API women residing in non-enclave areas. Access to culturally appropriate social supports and resources may be important for health promotion among API populations.

Air Pollution and Preterm Birth: Do Air Pollution Changes over Time Influence Risk in Consecutive Pregnancies among Low-Risk Women?

Since the 2000s, air pollution has generally continued to decrease in the U.S. To investigate preterm birth (PTB) risk associated with air pollutants in two consecutive pregnancies, we estimated exposures using modified Community Multiscale Air Quality models linked to the NICHD Consecutive Pregnancy Study. Electronic medical records for delivery admissions were available for 50,005 women with singleton births in 20 Utah-based hospitals between 2002-2010. We categorized whole pregnancy average exposures as high (>75th percentile), moderate (25-75) and low (<25). Modified Poisson regression estimated second pregnancy PTB risk associated with persistent high and moderate exposure, and increasing or decreasing exposure, compared to persistent low exposure. Analyses were adjusted for prior PTB, interpregnancy interval and demographic and clinical characteristics. Second pregnancy PTB risk was increased when exposure stayed high for sulfur dioxide (32%), ozone (17%), nitrogen oxides (24%), nitrogen dioxide (43%), carbon monoxide (31%) and for particles < 10 microns (29%) versus consistently low exposure. PTB risk tended to increase to a lesser extent for repeated PTB (19-21%) than for women without a prior PTB (22-79%) when exposure increased or stayed high. Area-level changes in air pollution exposure appear to have important consequences in consecutive pregnancies with increasing exposure associated with higher risk.