Deployment to Military Bases With Open Burn Pits and Respiratory and Cardiovascular Disease.

Importance: Many veterans who served in Afghanistan and Iraq during Operations Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF) were deployed to military bases with open burn pits and exposed to their emissions, with limited understanding of the long-term health consequences. Objective: To determine the association between deployment to military bases where open burn pits were used for waste disposal and the subsequent risk of developing respiratory and cardiovascular diseases. Design, Setting, and Participants: This retrospective observational cohort study used Veterans Health Administration medical records and declassified deployment records from the Department of Defense to assess Army and Air Force veterans who were deployed between 2001 and 2011 and subsequently received health care from the Veterans Health Administration, with follow-up through December 2020. Data were analyzed from January 2023 through February 2024. Exposure: Duration of deployment to military bases with open burn pits. Main Outcomes and Measures: Diagnosis of asthma, chronic obstructive pulmonary disease, interstitial lung disease, hypertension, myocardial infarction, congestive heart failure, ischemic stroke, and hemorrhagic stroke. Results: The study population included 459 381 OEF and OIF veterans (mean [SD] age, 31.6 [8.7] years; 399 754 [87.0%] male). Median (IQR) follow-up from end of deployment was 10.9 (9.4-12.7) years. For every 100 days of deployment to bases with burn pits, veterans experienced increased adjusted odds for asthma (adjusted odds ratio [aOR], 1.01; 95% CI, 1.01-1.02), chronic obstructive pulmonary disease (aOR, 1.04; 95% CI, 1.02-1.07), hypertension (aOR, 1.02; 95% CI, 1.02-1.03), and ischemic stroke (aOR, 1.06; 95% CI, 0.97-1.14). Odds of interstitial lung disease, myocardial infarction, congestive heart failure, or hemorrhagic stroke were not increased. Results based on tertiles of duration of burn pit exposures were consistent with those from the continuous exposure measures. Conclusions and Relevance: In this cohort study, prolonged deployment to military bases with open burn pits was associated with increased risk of developing asthma, COPD, and hypertension. The results also point to a possible increased risk in ischemic stroke. The novel ability to use integrated data on deployment and health outcomes provides a model for additional studies of the health impact of environmental exposures during military service.

Neonatal Outcomes are Similar between Patients with Resolved and Those with Persistent Oligohydramnios.

OBJECTIVE: Oligohydramnios (defined as amniotic fluid volume < 5 cm or deepest vertical pocket < 2 cm) is regarded as an ominous finding on prenatal ultrasound. Amniotic fluid, however, is not static, and to date, there have been no studies comparing perinatal outcomes in patients who are diagnosed with oligohydramnios that resolves and those who have persistent oligohydramnios. STUDY DESIGN: This is a secondary analysis of a National Institutes of Health-funded retrospective cohort study of singleton gestations delivered at a tertiary care hospital between 2002 and 2013 with mild hypertensive disorders and/or fetal growth restriction (FGR). Maternal characteristics, delivery, and neonatal information were abstracted by trained research nurses. Patients with a diagnosis of oligohydramnios were identified, and those with resolved versus persistent oligohydramnios at the time of delivery were compared. The primary outcome was a composite of neonatal resuscitation at delivery: administration of oxygen, bag-mask ventilation, continuous positive airway pressure, intubation, chest compression, or cardiac medication administration. Secondary outcomes included FGR, timing, and mode of delivery. RESULTS: Of 527 women meeting study criteria, 42 had oligohydramnios that resolved prior to delivery, whereas 485 had persistent oligohydramnios. There were no significant differences in patient demographics between groups. The gestational age at diagnosis was significantly lower for patients with resolved versus persistent oligohydramnios (median: 33.0 [interquartile range, IQR: 29.1-35.9] vs. 38.0 [IQR: 36.4-39.3], p < 0.001). There was not a substantial difference in rate of neonatal resuscitation (41 vs. 32%, p = 0.31). Patients with resolved oligohydramnios were more likely to have developed FGR than those with persistent oligohydramnios (55 vs. 36%, p < 0.02). There were no significant differences for gestational age at delivery, birth weight, or neonatal intensive care unit admission. CONCLUSION: Patients whose oligohydramnios resolved were diagnosed earlier yet had similar rates of neonatal resuscitation but higher rates of FGR than those who had persistent oligohydramnios. KEY POINTS: · When diagnosed earlier in pregnancy, oligohydramnios was more likely to resolve prenatally.. · Patients who were diagnosed with oligohydramnios earlier in pregnancy had higher rates of FGR.. · There were no differences in the rates of the composite outcome of need for neonatal resuscitation when comparing those with resolved versus those with persistent oligohydramnios. No differences in composite neonatal morbidity were noted between those with resolved versus persistent oligohydramnios..

Ambient air pollution and rate of spontaneous abortion.

Spontaneous abortion (SAB), defined as a pregnancy loss before 20 weeks of gestation, affects up to 30% of conceptions, yet few modifiable risk factors have been identified. We estimated the effect of ambient air pollution exposure on SAB incidence in Pregnancy Study Online (PRESTO), a preconception cohort study of North American couples who were trying to conceive. Participants completed questionnaires at baseline, every 8 weeks during preconception follow-up, and in early and late pregnancy. We analyzed data on 4643 United States (U.S.) participants and 851 Canadian participants who enrolled during 2013-2019 and conceived during 12 months of follow-up. We used country-specific national spatiotemporal models to estimate concentrations of particulate matter <2.5 µm (PM2.5), nitrogen dioxide (NO2), and ozone (O3) during the preconception and prenatal periods at each participant's residential address. On follow-up and pregnancy questionnaires, participants reported information on pregnancy status, including SAB incidence and timing. We fit Cox proportional hazards regression models with gestational weeks as the time scale to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association of time-varying prenatal concentrations of PM2.5, NO2, and O3 with rate of SAB, adjusting for individual- and neighborhood-level factors. Nineteen percent of pregnancies ended in SAB. Greater PM2.5 concentrations were associated with a higher incidence of SAB in Canada, but not in the U.S. (HRs for a 5 µg/m3 increase = 1.29, 95% CI: 0.99, 1.68 and 0.94, 95% CI: 0.83, 1.08, respectively). NO2 and O3 concentrations were not appreciably associated with SAB incidence. Results did not vary substantially by gestational weeks or season at risk. In summary, we found little evidence for an effect of residential ambient PM2.5, NO2, and O3 concentrations on SAB incidence in the U.S., but a moderate positive association of PM2.5 with SAB incidence in Canada.

Air pollution and fecundability in a North American preconception cohort study.

BACKGROUND: Animal and epidemiologic studies indicate that air pollution may adversely affect fertility. However, the level of evidence is limited and specific pollutants driving the association are inconsistent across studies. METHODS: We used data from a web-based preconception cohort study of pregnancy planners enrolled during 2013-2019 (Pregnancy Study Online; PRESTO). Eligible participants self-identified as female, were aged 21-45 years, resided in the United States (U.S.) or Canada, and were trying to conceive without fertility treatments. Participants completed a baseline questionnaire and bi-monthly follow-up questionnaires until conception or 12 months. We analyzed data from 8,747 participants (U.S.: 7,304; Canada: 1,443) who had been trying to conceive for < 12 cycles at enrollment. We estimated residential ambient concentrations of particulate matter < 2.5 µm (PM2.5), nitrogen dioxide (NO2), and ozone (O3) using validated spatiotemporal models specific to each country. We fit country-specific proportional probabilities regression models to estimate the association between annual average, menstrual cycle-specific, and preconception average pollutant concentrations with fecundability, the per-cycle probability of conception. We calculated fecundability ratios (FRs) and 95% confidence intervals (CIs) and adjusted for individual- and neighborhood-level confounders. RESULTS: In the U.S., the FRs for a 5-µg/m3 increase in annual average, cycle-specific, and preconception average PM2.5 concentrations were 0.94 (95% CI: 0.83, 1.08), 1.00 (95% CI: 0.93, 1.07), and 1.00 (95% CI: 0.93, 1.09), respectively. In Canada, the corresponding FRs were 0.92 (95% CI: 0.74, 1.16), 0.97 (95% CI: 0.87, 1.09), and 0.94 (95% CI: 0.80, 1.09), respectively. Likewise, NO2 and O3 concentrations were not strongly associated with fecundability in either country. CONCLUSIONS: Neither annual average, menstrual cycle-specific, nor preconception average exposure to ambient PM2.5, NO2, and O3 were appreciably associated with reduced fecundability in this cohort of pregnancy planners.

A prospective cohort study of preconception COVID-19 vaccination and miscarriage.

STUDY QUESTION: To what extent is preconception maternal or paternal coronavirus disease 2019 (COVID-19) vaccination associated with miscarriage incidence? SUMMARY ANSWER: COVID-19 vaccination in either partner at any time before conception is not associated with an increased rate of miscarriage. WHAT IS KNOWN ALREADY: Several observational studies have evaluated the safety of COVID-19 vaccination during pregnancy and found no association with miscarriage, though no study prospectively evaluated the risk of early miscarriage (gestational weeks [GW] <8) in relation to COVID-19 vaccination. Moreover, no study has evaluated the role of preconception vaccination in both male and female partners. STUDY DESIGN, SIZE, DURATION: An Internet-based, prospective preconception cohort study of couples residing in the USA and Canada. We analyzed data from 1815 female participants who conceived during December 2020-November 2022, including 1570 couples with data on male partner vaccination. PARTICIPANTS/MATERIALS, SETTING, METHODS: Eligible female participants were aged 21-45 years and were trying to conceive without use of fertility treatment at enrollment. Female participants completed questionnaires at baseline, every 8 weeks until pregnancy, and during early and late pregnancy; they could also invite their male partners to complete a baseline questionnaire. We collected data on COVID-19 vaccination (brand and date of doses), history of SARS-CoV-2 infection (yes/no and date of positive test), potential confounders (demographic, reproductive, and lifestyle characteristics), and pregnancy status on all questionnaires. Vaccination status was categorized as never (0 doses before conception), ever (≥1 dose before conception), having a full primary sequence before conception, and completing the full primary sequence ≤3 months before conception. These categories were not mutually exclusive. Participants were followed up from their first positive pregnancy test until miscarriage or a censoring event (induced abortion, ectopic pregnancy, loss to follow-up, 20 weeks' gestation), whichever occurred first. We estimated incidence rate ratios (IRRs) for miscarriage and corresponding 95% CIs using Cox proportional hazards models with GW as the time scale. We used propensity score fine stratification weights to adjust for confounding. MAIN RESULTS AND THE ROLE OF CHANCE: Among 1815 eligible female participants, 75% had received at least one dose of a COVID-19 vaccine by the time of conception. Almost one-quarter of pregnancies resulted in miscarriage, and 75% of miscarriages occurred <8 weeks' gestation. The propensity score-weighted IRR comparing female participants who received at least one dose any time before conception versus those who had not been vaccinated was 0.85 (95% CI: 0.63, 1.14). COVID-19 vaccination was not associated with increased risk of either early miscarriage (GW: <8) or late miscarriage (GW: 8-19). There was no indication of an increased risk of miscarriage associated with male partner vaccination (IRR = 0.90; 95% CI: 0.56, 1.44). LIMITATIONS, REASONS FOR CAUTION: The present study relied on self-reported vaccination status and infection history. Thus, there may be some non-differential misclassification of exposure status. While misclassification of miscarriage is also possible, the preconception cohort design and high prevalence of home pregnancy testing in this cohort reduced the potential for under-ascertainment of miscarriage. As in all observational studies, residual or unmeasured confounding is possible. WIDER IMPLICATIONS OF THE FINDINGS: This is the first study to evaluate prospectively the relation between preconception COVID-19 vaccination in both partners and miscarriage, with more complete ascertainment of early miscarriages than earlier studies of vaccination. The findings are informative for individuals planning a pregnancy and their healthcare providers. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institute of Health [R01-HD086742 (PI: L.A.W.); R01-HD105863S1 (PI: L.A.W. and M.L.E.)], the National Institute of Allergy and Infectious Diseases (R03-AI154544; PI: A.K.R.), and the National Science Foundation (NSF-1914792; PI: L.A.W.). The funders had no role in the study design, data collection, analysis and interpretation of data, writing of the report, or the decision to submit the paper for publication. L.A.W. is a fibroid consultant for AbbVie, Inc. She also receives in-kind donations from Swiss Precision Diagnostics (Clearblue home pregnancy tests) and Kindara.com (fertility apps). M.L.E. received consulting fees from Ro, Hannah, Dadi, VSeat, and Underdog, holds stock in Ro, Hannah, Dadi, and Underdog, is a past president of SSMR, and is a board member of SMRU. K.F.H. reports being an investigator on grants to her institution from UCB and Takeda, unrelated to this study. S.H.-D. reports being an investigator on grants to her institution from Takeda, unrelated to this study, and a methods consultant for UCB and Roche for unrelated drugs. The authors report no other relationships or activities that could appear to have influenced the submitted work. TRIAL REGISTRATION NUMBER: N/A.

Risk of Miscarriage in Relation to Seasonal Influenza Vaccination Before or During Pregnancy.

OBJECTIVE: To evaluate the association between seasonal influenza vaccination and miscarriage using data from an ongoing, prospective cohort study. METHODS: We analyzed 2013-2022 data from PRESTO (Pregnancy Study Online), a prospective prepregnancy cohort study of female pregnancy planners and their male partners in the United States and Canada. Female participants completed a baseline questionnaire and then follow-up questionnaires every 8 weeks until pregnancy, during early and late pregnancy, and during the postpartum period. Vaccine information was self-reported on all questionnaires. Miscarriage was identified from self-reported information during follow-up. Male partners were invited to complete a baseline questionnaire only. We used Cox proportional hazard models to estimate the hazard ratio (HR) and 95% CI for the association between vaccination less than 3 months before pregnancy detection through the 19th week of pregnancy and miscarriage, with gestational weeks as the time scale. We modeled vaccination as a time-varying exposure and used propensity-score fine stratification to control for confounding from seasonal and female partner factors. RESULTS: Of 6,946 pregnancies, 23.3% of female partners reported exposure to influenza vaccine before or during pregnancy: 3.2% during pregnancy (gestational age 4-19 weeks) and 20.1% during the 3 months before pregnancy detection. The miscarriage rate was 16.2% in unvaccinated and 17.0% among vaccinated participants. Compared with no vaccine exposure, influenza vaccination was not associated with increased rate of miscarriage when administered before (HR 0.99, 95% CI 0.81-1.20) or during (HR 0.83, 95% CI 0.47-1.47) pregnancy. Of the 1,135 couples with male partner vaccination data available, 10.8% reported vaccination less than 3 months before pregnancy. The HR for the association between male partner vaccination and miscarriage was 1.17 (95% CI 0.73-1.90). CONCLUSION: Influenza vaccination before or during pregnancy was not associated with miscarriage.

Immune response to COVID-19 vaccination in a population with a history of elevated exposure to per- and polyfluoroalkyl substances (PFAS) through drinking water.

BACKGROUND: Exposure to per- and polyfluoroalkyl substances (PFAS) has been linked to lower vaccine-induced antibody concentrations in children, while data from adults remains limited and equivocal. Characteristics of PFAS exposure and age at vaccination may modify such effects. OBJECTIVE: We used the mass administration of novel COVID-19 vaccines to test the hypothesis that prior exposure to environmentally-relevant concentrations of PFAS affect antibody response to vaccines in adolescents and adults. METHODS: Between April and June 2021, 226 participants aged 12-90 years with a history of exposure to PFAS in drinking water and who received an mRNA COVID-19 vaccine participated in our prospective cohort study. SARS-CoV-2 anti-spike and anti-nucleocapsid antibodies (IgG) were quantified before the first and second vaccine doses and again at two follow-ups in the following months (up to 103 days post dose 1). Serum PFAS concentrations (n = 39 individual PFAS) were measured once for each participant during baseline, before their first vaccination. The association between PFAS exposure and immune response to vaccination was investigated using linear regression and generalized estimating equation (GEE) models with adjustment for covariates that affect antibody response. PFAS mixture effects were assessed using weighted quantile sum and Bayesian kernel machine regression methods. RESULTS: The geometric mean (standard deviation) of perfluorooctane sulfonate and perfluorooctanoic acid serum concentrations in this population was 10.49 (3.22) and 3.90 (4.90) µg/L, respectively. PFAS concentrations were not associated with peak anti-spike antibody response, the initial increase in anti-spike antibody response following vaccination, or the waning over time of the anti-spike antibody response. Neither individual PFAS concentrations nor their evaluation as a mixture was associated with antibody response to mRNA vaccination against COVID-19. IMPACT STATEMENT: Given the importance of understanding vaccine response among populations exposed to environmental contaminants and the current gaps in understanding this relationship outside of early life/childhood vaccinations, our manuscript contributes meaningful data from an adolescent and adult population receiving a novel vaccination.

Predicting primary cesarean delivery in pregnancies complicated by gestational diabetes mellitus.

BACKGROUND: Prediction models have shown promise in helping clinicians and patients engage in shared decision-making by providing quantitative estimates of individual risk of important clinical outcomes. Gestational diabetes mellitus is a common complication of pregnancy, which places patients at higher risk of primary CD. Suspected fetal macrosomia diagnosed on prenatal ultrasound is a well-known risk factor for primary CD in patients with gestational diabetes mellitus, but tools incorporating multiple risk factors to provide more accurate CD risk are lacking. Such tools could help facilitate shared decision-making and risk reduction by identifying patients with both high and low chances of intrapartum primary CD. OBJECTIVE: This study aimed to develop and internally validate a multivariable model to estimate the risk of intrapartum primary CD in pregnancies complicated by gestational diabetes mellitus undergoing a trial of labor. STUDY DESIGN: This study identified a cohort of patients with gestational diabetes mellitus derived from a large, National Institutes of Health-funded medical record abstraction study who delivered singleton live-born infants at ≥34 weeks of gestation at a large tertiary care center between January 2002 and March 2013. The exclusion criteria included previous CD, contraindications to vaginal delivery, scheduled primary CD, and known fetal anomalies. Candidate predictors were clinical variables routinely available to a practitioner in the third trimester of pregnancy found to be associated with an increased risk of CD in gestational diabetes mellitus. Stepwise backward elimination was used to build the logistic regression model. The Hosmer-Lemeshow test was used to demonstrate goodness of fit. Model discrimination was evaluated via the concordance index and displayed as the area under the receiver operating characteristic curve. Internal model validation was performed with bootstrapping of the original dataset. Random resampling with replacement was performed for 1000 replications to assess predictive ability. An additional analysis was performed in which the population was stratified by parity to evaluate the model's predictive ability among nulliparous and multiparous individuals. RESULTS: Of the 3570 pregnancies meeting the study criteria, 987 (28%) had a primary CD. Of note, 8 variables were included in the final model, all significantly associated with CD. They included large for gestational age, polyhydramnios, older maternal age, early pregnancy body mass index, first hemoglobin A1C recorded in pregnancy, nulliparity, insulin treatment, and preeclampsia. Model calibration and discrimination were satisfactory with the Hosmer-Lemeshow test (P=.862) and an area under the receiver operating characteristic curve of 0.75 (95% confidence interval, 0.74-0.77). Internal validation demonstrated similar discriminatory ability. Stratification by parity demonstrated that the model worked well among both nulliparous and multiparous patients. CONCLUSION: Using information routinely available in the third trimester of pregnancy, a clinically pragmatic model can predict intrapartum primary CD risk with reasonable reliability in pregnancies complicated by gestational diabetes mellitus and may provide quantitative data to guide patients in understanding their individual primary CD risk based on preexisting and acquired risk factors.

Evaluating Chemical Mixtures in Epidemiological Studies to Inform Regulatory Decisions.

BACKGROUND: Epidemiological studies are increasingly going beyond the evaluation of health effects of individual chemicals to consider chemical mixtures. To our knowledge, the advantages and disadvantages of addressing chemical mixtures for informing regulatory decisions-as opposed to obtaining a more comprehensive understanding of etiology-has not been carefully considered. OBJECTIVES: We offer a framework for the study of chemical mixtures in epidemiological research intended to inform regulatory decisions. We identify a) the different ways mixtures originate (product source, pollution source, shared mode of action, or shared effect on health outcome), b) the use of indicator chemicals to address mixtures, and c) the requirements for epidemiological studies to be informative for regulatory purposes. DISCUSSION: The principal advantage of considering mixtures is to obtain a more complete understanding of the role of the chemical environment as a determinant of health. Incorporating other exposures may improve the assessment of the net effect of the chemicals of interest. However, the increased complexity and potential loss of generalizability may limit the value of studies of mixtures, especially for mixtures based on mode of action or shared health outcomes. Our recommended strategy is to successively assess the marginal contribution of individual chemicals, joint effects with other specific chemicals, and hypothesis-driven evaluation of mixtures rather than applying hypothesis-free data exploration methods. Although more ambitious statistical approaches to mixtures may, in time, be helpful for guiding regulation, the authors believe conventional methods for assessing individual and combined effects of chemicals remain preferable. https://doi.org/10.1289/EHP11899.

Enhancing Epidemiology's Impact on Policy: Mediation by Expert Committees.

Epidemiologic evidence is often a key source of information used by expert committees to guide policy decisions, yet epidemiologists rarely consider this audience for their research. For a better understanding of the pipeline from epidemiologic research to expert committee assessment to policy, several reports from the National Academies of Sciences, Engineering, and Medicine were reviewed and discussed with staff and committee members. The topics of these consensus committee assessments included health behaviors, medical care, and military exposures. The focus was often on emerging issues of immediate concern for which there was little relevant research available but a need for prompt action. Committees generally sought a comprehensive assessment of potential health effects of a given product or exposure, which often included social and behavioral health outcomes that are rarely addressed by epidemiologists. To enhance epidemiology's contribution to societal decisions, the choice of research topics should expand to consider emerging societal concerns. Research funding agencies need to be engaged as mediators between committee needs and the research community to stimulate contributory research. Improved communication of research needs to the epidemiology community would be beneficial to researchers aspiring to have an impact and to those who use epidemiologic information to help guide policy decisions.

Heat-related mortality in U.S. state and private prisons: A case-crossover analysis.

Rising temperatures and heatwaves increase mortality. Many of the subpopulations most vulnerable to heat-related mortality are in prisons, facilities that may exacerbate temperature exposures. Yet, there is scare literature on the impacts of heat among incarcerated populations. We analyzed data on mortality in U.S. state and private prisons from 2001-2019 linked to daily maximum temperature data for the months of June, July, and August. Using a case-crossover approach and distributed lag models, we estimated the association of increasing temperatures with total mortality, heart disease-related mortality, and suicides. We also examined the association with extreme heat and heatwaves (days above the 90th percentile for the prison location) and assessed effect modification by personal, facility, and regional characteristics. There were 12,836 deaths during summer months. The majority were male (96%) and housed in a state-operated prison (97%). A 10°F increase was associated with a 5.2% (95% CI: 1.5%, 9.0%) increase in total mortality and a 6.7% (95% CI: -0.6%, 14.0%) increase in heart disease mortality. The association between temperature and suicides was delayed, peaking around lag 3 (exposure at three days prior death). Two- and three-day heatwaves were associated with increased total mortality of 5.5% (95% CI: 0.3%, 10.9%) and 7.4% (95% CI: 1.6%, 13.5%), respectively. The cumulative effect (lags 1-3) of an extreme heat day was associated with a 22.8% (95% CI: 3.3%, 46.0%) increase in suicides. We found the greatest increase in mortality among people ≥ 65 years old, incarcerated less than one year, held in the Northeast region, and in urban or rural counties. These findings suggest that warm temperatures are associated with increased mortality in prisons, yet this vulnerable population's risk has largely been overlooked.

Outcomes among Neonates after a Diagnosis of Persistent or Transient Fetal Growth Restriction Delivered at Term.

OBJECTIVE: This study aimed to evaluate whether transient fetal growth restriction (FGR) that resolves prior to delivery confers a similar risk of neonatal morbidity as uncomplicated FGR that persists at term. STUDY DESIGN: This is a secondary analysis of a medical record abstraction study of singleton live-born pregnancies delivered at a tertiary care center between 2002 and 2013. Patients with fetuses that had either persistent or transient FGR and delivered at 38 weeks or later were included. Patients with abnormal umbilical artery Doppler studies were excluded. Persistent FGR was defined as estimated fetal weight (EFW) <10th percentile by gestational age from diagnosis through delivery. Transient FGR was defined as EFW <10th percentile on at least one ultrasound, but not on the last ultrasound prior to delivery. The primary outcome was a composite of neonatal morbidity: neonatal intensive care unit admission, Apgar's score <7 at 5 minutes, neonatal resuscitation, arterial cord pH <7.1, respiratory distress syndrome, transient tachypnea of the newborn, hypoglycemia, sepsis, or death. Baseline characteristics and obstetric and neonatal outcomes were compared using Wilcoxon's rank-sum and Fisher's exact test. Log binomial regression was used to adjust for confounders. RESULTS: Of 777 patients studied, 686 (88%) had persistent FGR and 91 (12%) had transient FGR. Patients with transient FGR were more likely to have a higher body mass index, gestational diabetes, diagnosed with FGR earlier in pregnancy, have spontaneous labor, and deliver at later gestational ages. There was no difference in the composite neonatal outcome (relative risk = 1.03, 95% confidence interval [CI] 0.72, 1.47) for transient versus persistent FGR after adjusting for confounders (adjusted relative risk = 0.79, 95% CI 0.54, 1.17). There were no differences in cesarean delivery or delivery complications between groups. CONCLUSION: Neonates born at term after transient FGR do not appear to have differences in composite morbidity compared with those where uncomplicated FGR persists at term. KEY POINTS: · No differences in neonatal outcomes in uncomplicated persistent versus transient FGR at term.. · Transient FGR pregnancies more likely to deliver at later gestational ages.. · No differences in mode of delivery or obstetric complications in persistent versus transient FGR at term..

Association Between Change in Physical Activity During Pregnancy and Infant Birth Weight.

OBJECTIVE: We assessed whether total, recreational, and non-recreational physical activity (PA) assessed twice during pregnancy, and its change, were associated with infant birth weight and small for gestational age (SGA). METHODS: We included 1467 Pregnancy, Infection, and Nutrition 3 Study participants who self-reported PA at time 1 (T1: 17-22 weeks' gestation) and time 2 (T2: 27-30 weeks' gestation). We assessed last week absolute intensities of PA (moderate: 4.7-7.1 METs; and vigorous: > 7.1 METs) and perceived intensities. Change in hours/week of PA was assessed continuously or categorically (increase or decrease ≥ 1 hour, and no change). Associations of continuous PA hours/week at T1, T2, and its change, with sex-specific z-scores of birth weight, were assessed using multivariable linear robust regressions. We used logistic regressions to assess categorical PA measures with SGA. Models were adjusted for adequacy of maternal weight gain, general health, maternal age, parity, race/ethnicity, and smoking. RESULTS: Hours/week of total and recreational absolute intensities of PA at T1, T2, and its change were generally not associated with birth weight, although two measures of non-recreational PA at T2 and its change were associated with increased birth weight. Perceived intensities of PA (at T1, T2, and its change) were largely not associated with sex-specific z-scores of infant birth weight. Absolute and perceived intensity PA were not associated with SGA. CONCLUSIONS FOR PRACTICE: In this observational cohort, increases and decreases in PA during pregnancy were not associated with differential changes in birthweight or SGA.

Burn Pit Exposure Assessment to Support a Cohort Study of US Veterans of the Wars in Iraq and Afghanistan.

OBJECTIVE: For a cohort study of veterans' health conditions, we conducted an exposure assessment for 109 bases in Iraq and Afghanistan and 17 outside transit site bases. METHODS: The Department of Defense records were used to determine burn pit usage and waste disposal methods for each base in each year during the period of 2001 to 2014. RESULTS: In the final cohort of 475,326 veterans, who had more than 80% of their deployment time characterized by our exposure matrix, only 14.5% were found to have no burn pit exposure. The 2009 Department of Defense regulations on burn pits did produce changes in waste segregation, as well as adding incineration and local disposal of waste. CONCLUSION: Most Iraq and Afghanistan veterans were stationed on bases that had burn pits, although the contents disposed of in the burn pits changed over time.

Can Cross-Sectional Studies Contribute to Causal Inference? It Depends.

Cross-sectional studies-often defined as those in which exposure and outcome are assessed at the same point in time-are frequently viewed as minimally informative for causal inference. While cross-sectional studies may be susceptible to reverse causality, may be limited to assessment of disease prevalence rather than incidence, or may only provide estimates of current rather than past exposures, not all cross-sectional studies suffer these limitations. Moreover, none of these concerns are unique to or inherent in the structure of a cross-sectional study. Regardless of when exposure and disease were ascertained relative to one another, a cross-sectional study may provide insights into the causal effects of exposure on disease incidence. Simply labeling a study as "cross-sectional" and assuming that 1 or more of these limitations exist and are materially important fails to recognize the need for a more nuanced assessment and risks discarding evidence that may be useful in assessing causal relationships.