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.

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.

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..

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.

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.

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.

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.

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.

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..

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.

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.

2198. Healthcare Utilization During Acute Medically Attended Respiratory Syncytial Virus (RSV) Episodes among Infants in the United States

Background

Healthcare utilization during acute medically attended (MA) RSV-associated lower respiratory tract infection (LRTI) episodes remains poorly characterized, particularly among term infants without comorbidities. Describing the care incurred during these episodes may provide important information regarding the impact of MA RSV LRTI.

Objective: Estimate the occurrence and average number of outpatient, emergency department (ED), and inpatient visits during infants' first RSV season.

Methods

Using deidentified insurance claims data (MarketScan Commercial ®, MSC; MarketScan Medicaid ®, MSM; Optum Clinformatics ®, OC), we assembled a cohort of infants born in the United States between April 1, 2016 and February 29, 2020 and identified their first MA RSV LRTI episode during their first RSV season. We defined an RSV episode as the 7 days following an index RSV diagnosis (inclusive of the diagnosis date), allowing for two alternative definitions of the index diagnosis—a specific definition, based on ICD-10 codes explicitly indicating RSV, and a sensitive definition, including codes for unspecified bronchiolitis. We calculated the average number of outpatient, ED, and inpatient visits during this episode, stratifying estimates by gestational age and the presence/absence of comorbidities. We also calculated the proportion of episodes involving a given place of service.

Results

Using the specific (sensitive) definitions, infants averaged 1.11 (1.19), 0.90 (0.89), and 1.56 (1.39) outpatient visits during their first acute RSV episode, in the MSC, MSM, and OC datasets, respectively (Table). They averaged 0.35 (0.23), 0.51 (0.47), and 0.39 (0.23) visits to the ED and 0.28 (0.14), 0.25 (0.14), and 0.23 (0.11) inpatient stays. While MA RSV LRTI episodes among infants who were preterm and/or had other comorbidities (comorbidity groups B and C) were more likely to involve an ED or inpatient visit, up to 21% (10%) of episodes among otherwise healthy term infants involved an inpatient stay.

Conclusion

Up to 1 in 5 infants experiencing an MA RSV LRTI episode during their first RSV season visited an inpatient setting, including between 9% and 21% of otherwise healthy term infants.

This study was funded by Sanofi and AstraZeneca.

Disclosures

Jason Gantenberg, PhD, MPH, Sanofi: Grant/Research Support Robertus van Aalst, PhD, MSc, Sanofi: Stocks/Bonds David R. Diakun, BS, Sanofi: Employed by IBM Watson Health which was contracted by Sanofi to perfom outcomes research|Sobi: Employed by IBM Watson Health which was contracted by Sobi to conduct the study Christopher B. Nelson, PhD MPH, Sanofi: employee|Sanofi: Stocks/Bonds David A. Savitz, PhD, Sanofi-Pasteur: Grant/Research Support|Sanofi-Pasteur: Honoraria Andrew R. Zullo, PharmD, PhD, Sanofi: Grant/Research Support.

Risk factors for respiratory distress syndrome among high-risk early-term and full-term deliveries

OBJECTIVE

To identify whether risk factors for respiratory distress syndrome (RDS) differ between early-term and full-term births.

STUDY DESIGN

This is a secondary analysis of a large NIH-funded retrospective cohort study including patients who delivered at a tertiary-care obstetric hospital between January 2002 and March 2013 with comorbid diabetes, hypertensive disorders, and/or fetal growth restriction (FGR). Pregnancies complicated by severe preeclampsia and multifetal gestations were excluded. Maternal characteristics, delivery information, and neonatal information were abstracted by trained clinicians blinded to the comorbidity leading to study inclusion. In this secondary analysis of the infant health outcomes of pregnancies with one or more of the qualifying conditions, risk factors for RDS among neonates born early term (37w0d-38w6d gestation) were compared to risk factors for RDS among full-term neonates (39w0d-40w6d).

RESULTS

Among 10,532 singleton newborns, there were 99 cases of early-term RDS (0.94%) and 95 cases of full-term RDS (0.90%). Maternal demographics were similar between those with and without RDS in both groups. Among early-term infants, lower gestational age, presence of meconium, non-spontaneous labor, and cesarean delivery were positively associated with RDS, whereas hypertensive disorders, diabetes, FGR, and many other comorbid delivery conditions were not. The strongest risk factor for RDS among early-term infants was delivery via cesarean (RR 1.98, 95% CI 1.31, 3.01). Among full-term neonates, cesarean delivery was also positively associated with RDS, although presence of meconium, chorioamnionitis, and endometritis were all stronger risk factors with RRs >2.0.

CONCLUSIONS

In this cohort of high-risk term deliveries, maternal demographics and comorbidities were found not to be associated with increased risk for RDS, but novel risk factors for RDS after 37 weeks' gestation - chorioamnionitis and endometritis - were identified. A focus on preventing infectious comorbidities may help reduce incidence of RDS at full-term.Key PointsRDS risk factors vary by gestational age.Novel risk factors for RDS at full-term identified.Intrauterine inflammation associated with RDS at term.

Exposure to metal mixtures and neuropsychological functioning in middle childhood

Elevated exposure to multiple trace metals can be neurotoxic even at relatively low levels. These findings are primarily evident from adult occupational studies as well as in children exposed prenatally or in early childhood. Less research has focused on the neurodevelopmental impacts of exposure to metals among school-aged children. We examined associations between exposure to a mixture of four metals (arsenic, cadmium, manganese, lead) measured in hair and markers of cognition, attention, and behavior among 222 6-12 year old children who participated in a 2009-2010 neurodevelopmental follow-up to the C8 Health Project. Using quantile-based g-computation we estimated the adjusted overall metal mixture effect ψ (95 % CI) as the change in outcome per decile increase in all metals in the mixture. Hair metal levels varied by metal, with cadmium being lowest (median 0.007, interquartile range (IQR) 0.013 μg/g) and lead the highest concentration (median 0.152, IQR 0.252 μg/g). Children's cognitive skills and development, attention/impulsivity, and behavior were all close to standardized population means. Each decile increase in all metals was associated with a Full Scale IQ reduction of 1.01 points (95 % confidence interval (CI) -1.88, -0.15) and Verbal IQ reduction of 1.11 points (95 % CI -1.97, -0.25), adjusted for child age, sex, secondhand smoke exposure, HOME score, maternal education, maternal IQ, and examiner. Maternal report of ADHD-like behaviors and executive functioning also showed adverse associations with the metal mixture. Our findings suggest that similar to exposure during prenatal and early childhood periods, recent exposure to metals during middle childhood is associated with adverse neurodevelopmental consequences. Middle childhood may also be a developmental window of susceptibility to the negative consequences of exposure to environmental neurotoxicants.

Provision of Air Conditioning and Heat-Related Mortality in Texas Prisons

IMPORTANCE

There is a large body of epidemiologic evidence that heat is associated with increased risk of mortality. One of the most effective strategies to mitigate the effects of heat is through air conditioning (AC); Texas regulates the internal temperature of jails to stay between 65 and 85 °F degrees, but these same standards do not apply to state and private prisons.

OBJECTIVE

To analyze whether heat during warm months is associated with an increased risk of mortality in Texas prisons without AC.

DESIGN, SETTING, AND PARTICIPANTS

This case-crossover study included individuals who died in Texas prisons between 2001 and 2019. The association of heat in warm months with mortality in Texas prisons with and without AC was estimated. Data analysis was conducted from January to April 2022.

EXPOSURES

Increasing daily heat index above 85 °F and extreme heat days (days above the 90th percentile heat index for the prison location).

MAIN OUTCOMES AND MEASURES

Daily mortality in Texas prisons.

RESULTS

There were 2083 and 1381 deaths in prisons without and with AC, respectively, during warm months from 2001 to 2019. Most of the deceased were male (3339 of 3464 [96%]) and the median (IQR) age at death was 54 (45-62) years. A 1-degree increase above 85 °F heat index and an extreme heat day were associated with a 0.7% (95% CI, 0.1%-1.3%) and a 15.1% (95% CI, 1.3%-30.8%) increase in the risk of mortality in prisons without AC, respectively. Approximately 13% of mortality or 271 deaths may be attributable to extreme heat during warm months between 2001 to 2019 in Texas prison facilities without AC. In prisons with AC, a negative percentage change in mortality risk was observed, although the 95% CI crossed zero (percentage change in mortality risk: -0.6%; 95% CI, -1.6% to 0.5%). The estimates in prisons without AC were statistically different than the estimates in prisons with AC (P = .05).

CONCLUSIONS AND RELEVANCE

This study found an average of 14 deaths per year between 2001 to 2019 were associated with heat in Texas prisons without AC vs no deaths associated with heat in prisons with AC. Adopting an AC policy in Texas prisons may be important for protecting the health of one of our most vulnerable populations.

Development and Internal Validation of a Risk Prediction Model for Acute Cardiovascular Morbidity in Preeclampsia

BACKGROUND

Persons with preeclampsia are at increased short-term risk of adverse cardiovascular outcomes during pregnancy and the early postpartum period. We aimed to develop and internally validate a risk assessment tool to predict acute cardiovascular morbidity in preeclampsia.

METHODS

The study was conducted at an academic obstetric hospital. Participants with preeclampsia at delivery between 2007 and 2017 were included. A model to predict acute cardiovascular morbidity at delivery and within 6 weeks postpartum was developed and evaluated. The primary composite outcome included pulmonary edema/acute heart failure, myocardial infarction, aneurysm, cardiac arrest/ventricular fibrillation, heart failure/arrest during surgery or procedure, cerebrovascular disorders, cardiogenic shock, conversion of cardiac rhythm, and difficult-to-control severe hypertension. We assessed model discrimination and calibration. We used bootstrapping for internal validation.

RESULTS

4,171 participants with preeclampsia were included. The final model comprised 8 variables. Predictors positively associated with acute cardiovascular morbidity (presented as odds ratio [OR] with 95% confidence interval [CI]) were: gestational age at delivery (20-36 weeks 5.36 [3.67, 7.82]; 37-38 weeks 1.75 [1.16, 2.64]), maternal age (≥40 years 1.65 [1.00, 2.72]; 35-39 years 1.49 [1.07, 2.09]), and prior cesarean delivery (1.47, [1.01, 2.13]). The model had an area under the receiver operating characteristic curve of 0.72 (95% CI [0.69, 0.74]). Moreover, it was adequately calibrated and performed well on internal validation.

CONCLUSIONS

This risk prediction tool identified women with preeclampsia at highest risk of acute cardiovascular morbidity. If externally validated, this tool may facilitate early interventions aimed at preventing adverse cardiovascular outcomes in pregnancy and postpartum.

Health Outcomes Associated With Clinician-initiated Delivery for Hypertensive Disorders at 34-38 Weeks' Gestation

BACKGROUND

Clinicians caring for the nearly 10% of patients in the United States with nonsevere hypertensive disorders in late pregnancy need better evidence to balance risks and benefits of clinician-initiated delivery.

METHODS

We conducted a record-based cohort study of maternal and infant health outcomes among deliveries from 2002-2013 at Women & Infants Hospital of Rhode Island. Participants had gestational hypertension or nonsevere preeclampsia before 39 weeks' gestation (N=4,295). For each gestational week from 34 to 38, we compared outcomes between clinician-initiated deliveries (induction of labor or prelabor cesarean) and those not initiated in that week, using propensity score models to control confounding by indication.

RESULTS

The analysis predicted an increment in risk of adverse maternal and infant outcomes sustained through week 37 if all patients underwent clinician-initiated delivery, with risk differences on the order of 0.2 for maternal outcomes and 0.3 for infant outcomes weeks 34 and 35. For women undergoing clinician-initiated delivery, the analysis identified increased risk of progression to severe disease in weeks 35 and 36, increases in all adverse infant outcomes only in week 34, increases in Neonatal Intensive Care Unit admission and infant hospital stay in weeks 35 and 36, and no meaningful increase in any of the adverse outcomes in weeks 37 or 38.

CONCLUSIONS

We estimate that hypertensive pregnancies chosen for intervention were minimally harmed by early delivery after 34 weeks' gestation but predict benefit from extension to 37 weeks. Our study also showed adverse infant health consequences associated with routine delivery prior to 37 weeks.

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, limited to assessment of disease prevalence rather than incidence, or 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 nonetheless provide insights into the causal effects of exposure on disease incidence. Simply labeling a study as "cross-sectional" and assuming that one 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.

A prospective study of preconception asthma and spontaneous abortion

PURPOSE

To evaluate the relationships among history of asthma, asthma severity, and spontaneous abortion (SAB).

METHODS

Pregnancy Study Online is a preconception cohort study of North American couples. During the preconception period, female participants reported their history of physician-diagnosed asthma, age at first diagnosis, and use of asthma medications in the previous 4 weeks. Asthma severity was classified by medication use proximal to conception, from level 0 to 3 in increasing severity. Pregnancy and SAB were identified using data from follow-up questionnaires. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Among 6325 participants who conceived, 19% experienced SAB and 17% reported a history of asthma. There was no appreciable association between asthma history and SAB incidence (HR = 0.98; 95% CI: 0.84, 1.14). HRs comparing severity levels 0, 1, and 2-3 with no asthma were 0.82 (95% CI: 0.67, 1.01), 1.20 (95% CI: 0.91, 1.60), and 1.31 (95% CI: 0.97, 1.78), respectively. Among women who conceived without the use of fertility treatment, level 2-3 severity was associated with SAB (HR = 1.39; 95% CI: 1.02, 1.89).

CONCLUSIONS

While history of asthma diagnosis was not materially associated with SAB, having severe asthma (based on medication use) was associated with greater SAB risk.

Term Labor Induction and Cesarean Delivery Risk among Obese Women with and without Comorbidities

OBJECTIVE

Findings of the recent ARRIVE (A Randomized Trial of Induction Versus Expectant Management) trial, showing reduced cesarean risk with elective labor induction among low-risk nulliparous women at 39 weeks' gestation, have the potential to change interventional delivery practices but require examination in wider populations. The aim of this study was to identify whether term induction of labor was associated with reduced cesarean delivery risk among women with obesity, evaluating several maternal characteristics associated with obesity, induction, and cesarean risk.

STUDY DESIGN

We studied administrative records for 66,280 singleton, term births to women with a body mass index ≥30, without a prior cesarean delivery, in New York City from 2008 to 2013. We examined elective inductions in 39 and 40 weeks' gestation and calculated adjusted risk ratios for cesarean delivery risk, stratified by parity and maternal age. We additionally evaluated medically indicated inductions at 37 to 40 weeks among women with obesity and diabetic or hypertensive disorders, comorbidities that are strongly associated with obesity.

RESULTS

Elective induction of labor was associated with a 25% (95% confidence interval: 19-30%) lower adjusted risk of cesarean delivery as compared with expectant management at 39 weeks of gestation and no change in risk at 40 weeks. Patterns were similar when stratified by parity and maternal age. Risk reductions in week 39 were largest among women with a prior vaginal delivery. Women with comorbidities had reduced cesarean risk with early term induction and in 39 weeks.

CONCLUSION

Labor induction at 39 weeks was consistently associated with reduced risk of cesarean delivery among women with obesity regardless of parity, age, or comorbidity status. Cesarean delivery findings from induction trials at 39 weeks among low-risk nulliparous women may generalize more broadly across the U.S. obstetric population, with potentially larger benefit among women with a prior vaginal delivery.

KEY POINTS

· We found reduced cesarean risk with induction at 39 weeks.. · Results were consistent for age and comorbidity subgroups.. · Risk reductions were largest among multiparous women..

OUP accepted manuscript

Background

Respiratory syncytial virus (RSV) is a leading cause of infant hospitalization in the United States. Preterm infants and those with select comorbidities are at highest risk of RSV-related complications. However, morbidity due to RSV infection is not confined to high-risk infants. We estimated the burden of medically attended (MA) RSV-associated lower respiratory tract infection (LRTI) among infants in the United States.

Methods

We analyzed commercial (MarketScan Commercial [MSC], Optum Clinformatics [OC]), and Medicaid (MarketScan Medicaid [MSM]) insurance claims data for infants born between April 2016 and February 2020. Using both specific and sensitive definitions of MA RSV LRTI, we estimated the burden of MA RSV LRTI during infants’ first RSV season, stratified by gestational age, comorbidity status, and highest level of medical care associated with the MA RSV LRTI diagnosis.

Results

According to the specific definition 75.0% (MSC), 78.6% (MSM), and 79.6% (OC) of MA RSV LRTI events during infants’ first RSV season occurred among term infants without known comorbidities.

Conclusions

Term infants without known comorbidities account for up to 80% of the MA RSV LRTI burden in the United States during infants’ first RSV season. Future prevention efforts should consider all infants.

1337. Medically Attended (MA) Illness Due to Respiratory Syncytial Virus (RSV) Infection among Infants in the United States during the 2016–17, 2017–18, 2018–19, and 2019–20 RSV Seasons: The Need for All-Infant Protection

Background

RSV-associated lower respiratory tract infection (LRTI) is the leading cause of infant hospitalization. Most studies of RSV have focused on infants with underlying comorbidities, including prematurity. The purpose of this analysis is to describe the burden of RSV LRTI across all medical settings and in all infants experiencing their first RSV season.

Methods

Using de-identified claims data from two commercial (MarketScan Commercial, MSC; Optum Clinformatics, OC) and one public (MarketScan Medicaid, MSM) insurance database, we estimated the prevalence of MA RSV LRTI among infants born between April 1, 2016 and June 30, 2019 in their first RSV season. Estimates were made by gestational age, presence/absence of comorbidities, and setting (inpatient, emergency department and outpatient). Due to limited laboratory testing, we defined MA RSV LRTI using two sets of ICD-10-CM diagnosis codes: a specific definition (identifying RSV explicitly) and a sensitive definition that included unspecified bronchiolitis. The first specific diagnosis triggered a search for another MA RSV LRTI diagnosis (either specific or sensitive) within the next 7 days. In the sensitive analysis, the first diagnosis was allowed to meet the sensitive definition. Setting was recorded as the highest level of care attached to a MA RSV LRTI diagnosis within this 7-day period.

Results

Using the specific (sensitive) definitions, 4.2% (12.2%), 6.8% (16.8%), and 2.7% (7.2%) of newborns had an MA RSV LRTI diagnosis during their first respiratory season across the MSC, MSM, and OC datasets (Table 1). Term infants without comorbidities accounted for 77% (83%), 79% (86%), and 80 (81%) of all MA RSV LRTI, and 21% (10%), 19% (10%), and 21% (10%) of all infants with MA RSV LRTI had an inpatient hospital stay (Table 2). Term infants without comorbidities accounted for 69% (68%), 67% (79%), and 73% (73%) of all MA RSV LRTI inpatients (Table 2).

Conclusion

In commercial and public claims data, during their first RSV season, term infants without comorbidities accounted for a sizable majority of inpatient, emergency room, and outpatient encounters for RSV LRTI in the US. To address the burden of RSV LRTI, future RSV prevention efforts should target all infants.

Funding

Sanofi Pasteur, AstraZeneca

Disclosures

Jason Gantenberg, MPH, Sanofi Pasteur (Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support) Nicole Zimmerman, MS, IBM Watson Health (Employee, Nicole Zimmerman is an employee of IBM, which was compensated by Sanofi to complete this work.)Sanofi (Other Financial or Material Support, Nicole Zimmerman is an employee of IBM, which was compensated by Sanofi to complete this work.) Andrew R. Zullo, PharmD, PhD, ScM, Sanofi Pasteur (Grant/Research Support, Research Grant or Support) Brendan Limone, PharmD, PharmD, Sanofi Pasteur (Other Financial or Material Support, IBM was contracted by Sanofi to perform analysis) Clarisse Demont, n/a, Sanofi Pasteur (Employee, Shareholder) Sandra S. Chaves, MD, MSc, Sanofi Pasteur (Employee) William V. La Via, MD, AstraZeneca (Shareholder)Sanofi Pasteur (Employee) Christopher Nelson, PhD, Epidemiology, Sanofi Pasteur (Employee) Christopher Rizzo, MD, Sanofi (Employee) David A. Savitz, PhD, Sanofi Pasteur (Grant/Research Support) Robertus Van Aalst, MSc, Sanofi Pasteur (Employee, Shareholder)

Changes in Adverse Pregnancy Outcomes Associated With the COVID-19 Pandemic in the United States

This cross-sectional study evaluates the change in rates of pregnancy complications during the COVID-19 pandemic among pregnant women with commercial health insurance across the US.

Accuracy of self-reported birth outcomes relative to birth certificate data in an Internet-based prospective cohort study

BACKGROUND

The accuracy of birth outcome data provided by Internet-based cohort study participants has not been well studied.

METHODS

We compared self-reported data on birth characteristics in Pregnancy Study Online (PRESTO), an Internet-based prospective cohort study of North American pregnancy planners, with birth certificate data. At enrolment, participants were aged 21-45 years, attempting conception, and not using fertility treatment. Women completed online questionnaires during preconception, early and late pregnancy, and postpartum. We requested birth certificate data during 2014-2019 from seven health departments in states with the most participants. After restricting to singleton births, we assessed specificity, sensitivity, and agreement comparing self-reported data from postpartum questionnaires with birth certificate data for gestational age at delivery (GA) and birthweight (grams). Our primary measure of self-reported GA (weeks) was calculated as [280-(due date-birth date)]/7. We used log-binomial regression to assess predictors of agreement.

RESULTS

We linked 85% (771/909) of women in selected states. Median age of women was 30 years (range: 21-42), 84% had ≥ 16 years of education, nearly 96% were married, 12% had household incomes <$50 000, 32% were parous, and 85% identified as non-Hispanic White. Median recall interval was 6 months. Among those with self-reported data, 89% reported the same GA as the birth certificate and 98% reported GA within 1 week of the birth certificate. Self-report of preterm birth (GA < 37 weeks) agreed with information from birth certificates for 100% of women; sensitivity was 100%, and specificity was 99%. Self-reported low birthweight (<2500 grams) agreed with birth certificates for 93% of women; sensitivity and specificity were 93% and ≥99%, respectively. Predictors of poorer agreement included higher parity and longer pregnancy attempt time for GA, and lower education and longer recall interval for birthweight.

CONCLUSION

Self-reported data on GA and birthweight from an Internet-based cohort showed high accuracy compared with birth certificates.

Ambient heat and stillbirth in Northern and Central Florida

BACKGROUND

Elevated temperature is well-recognized as a health hazard, and may be particularly harmful to pregnant women, including increasing risk of stillbirth. We conducted a study in Northern and Central Florida, an area prone to periodic extreme heat but with significant seasonal variation, focusing on the most socioeconomically vulnerable populations least able to mitigate the impact of heat.

METHODS

We obtained electronic health records data from the OneFlorida Data Trust for the period 2012-2017, with 1876 stillbirths included in the analysis. We used a case-crossover design to examine the risk of stillbirth associated with acute exposures to elevated heat prior to the outcome, contrasting the case period (the week preceding the stillbirth) with a control period (the week prior to the case period and the week after the stillbirth). Average heat index and maximum warning level during the case and control periods of each woman were assigned by ZIP code. Conditional logistic regression models were used to assess the association between stillbirth and heat exposure, controlling for PM_2.5 and O₃.

RESULTS

The adjusted odds ratio showed no overall association with stillbirth except for a weak association for exposure above the 90th percentile which was larger among the most socioeconomically deprived and non-Hispanic Black women. In the hot months, there was a clear association for all indices of heat exposure, but largest again for the most socioeconomically deprived population (aOR = 2.4, 95% CI: 1.2-5.2 in the 4th vs. 1st quartile) and among non-Hispanic Black women (aOR = 1.8, 95% CI: 1.0-3.2 in the 4th vs. 1st quartile).

CONCLUSIONS

Our results provide further evidence that elevated ambient heat is related to stillbirth and encourage a focus on the most susceptible individuals and possible clinical pathways.

Point: Reconciling Epidemiology's Aspirations and Capabilities

Interpreting the results of epidemiologic studies calls for objectivity and rigorous scrutiny, acknowledging the limitations that temper the applicability of the findings to public health action. Current trends have posed new challenges to balancing goals of scientific objectivity and validity with public health applications. The ongoing tension between epidemiology's aspirations and capability has several sources: the need to overpromise in research proposals, compromising methodological rigor because of public health importance, defending findings in the face of hostile critics, and appealing to core constituencies who have specific expectations from the research.

Human Health Exposure Analysis Resource (HHEAR): A model for incorporating the exposome into health studies

BACKGROUND

Characterizing the complexity of environmental exposures in relation to human health is critical to advancing our understanding of health and disease throughout the life span. Extant cohort studies open the door for such investigations more rapidly and inexpensively than launching new cohort studies and the Human Health Exposure Analysis Resource (HHEAR) provides a resource for implementing life-stage exposure studies within existing study populations. Primary challenges to incorporation of environmental exposure assessment in health studies include: (1) lack of widespread knowledge of biospecimen and environmental sampling and storage requirements for environmental exposure assessment among investigators; (2) lack of availability of and access to laboratories capable of analyzing multiple environmental exposures throughout the life-course; and (3) studies lacking sufficient power to assess associations across life-stages. HHEAR includes a consortium of researchers with expertise in laboratory analyses, statistics and logistics to overcome these limitations and enable inclusion of exposomics in human health studies.

OBJECTIVE

This manuscript describes the structure and strengths of implementing the harmonized HHEAR resource model, and our approaches to addressing challenges. We describe how HHEAR incorporates analyses of biospecimens and environmental samples and human health studies across the life span - serving as a model for incorporating environmental exposures into national and international research. We also present program successes to date.

DISCUSSION

HHEAR provides a full-service laboratory and data analysis exposure assessment resource, linking scientific, life span, and toxicological consultation with both laboratory and data analysis expertise. HHEAR services are provided without cost but require NIH, NCI, NHLBI, or ECHO funding of the original cohort; internal HHEAR scientific review and approval of a brief application; and adherence to data sharing and publication policies. We describe the benefits of HHEAR's structure, collaborative framework and coordination across project investigators, analytical laboratories, biostatisticians and bioinformatics specialists; quality assurance/quality control (QA/QC) including integrated sample management; and tools that have been developed to support the research (exposure information pages, ontology, new analytical methods, common QA/QC approach across laboratories, etc.). This foundation supports HHEAR's inclusion of new laboratory and statistical analysis methods and studies that are enhanced by including targeted analysis of specific exposures and untargeted analysis of chemicals associated with phenotypic endpoints in biological and environmental samples.

CONCLUSION

HHEAR is an interdisciplinary team of toxicologists, epidemiologists, laboratory scientists, and data scientists across multiple institutions to address broad and complex questions that benefit from integrated laboratory and data analyses. HHEAR's processes, features, and tools include all life stages and analysis of biospecimens and environmental samples. They are available to the wider scientific community to augment studies by adding state of the art environmental analyses to be linked to human health outcomes.

Guidance for design and analysis of observational studies of fetal and newborn outcomes following COVID-19 vaccination during pregnancy

COVID-19 vaccines are now being deployed as essential tools in the public health response to the global SARS-CoV-2 pandemic. Pregnant individuals are a unique subgroup of the population with distinctive considerations regarding risk and benefit that extend beyond themselves to their fetus/newborn. As a complement to traditional pharmacovigilance and clinical studies, evidence to comprehensively assess COVID-19 vaccine safety in pregnancy will need to be generated through observational epidemiologic studies in large populations. However, there are several unique methodological challenges that face observational assessments of vaccination during pregnancy, some of which may be more pronounced for COVID-19 studies. In this contribution, we discuss the most critical study design, data collection, and analytical issues likely to arise. We offer brief guidance to optimize the quality of such studies to ensure their maximum value for informing public health decision-making.

Risk Factors for Progression From Gestational Diabetes to Postpartum Type 2 Diabetes: A Review

Gestational diabetes mellitus (GDM) complicates 6% to 8% of pregnancies and up to 50% of women with GDM progress to type 2 diabetes mellitus (DM) within 5 years postpartum. Clinicians have little guidance on which women are most at risk for DM progression or when evidence-based prevention strategies should be implemented in a woman's lifecycle. To help address this gap, the authors review identifiable determinants of progression from GDM to DM across the perinatal period, considering prepregnancy, pregnancy, and postpartum periods. The authors categorize evidence by pathways of risk including genetic, metabolic, and behavioral factors that influence progression to DM among women with GDM.