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BACKGROUND: Parametric g-computation is an attractive analytic framework to study the health effects of air pollution. Yet, the ability to explore biologically relevant exposure windows within this framework is underdeveloped. OBJECTIVES: We outline a novel framework for how to incorporate complex lag-responses using distributed lag models (DLMs) into parametric g-computation analyses for survival data. We call this approach "g-survival-DLM" and illustrate its use examining the association between [PM.sub.2.5] during pregnancy and the risk of preterm birth (PTB). METHODS: We applied the g-survival-DLM approach to estimate the hypothetical static intervention of reducing average [PM.sub.2.5] in each gestational week by 20% on the risk of PTB among 9,403 deliveries from Beth Israel Deaconess Medical Center, Boston, Massachusetts, 2011-2016. Daily [PM.sub.2.5] was taken from a 1-km grid model and assigned to address at birth. Models were adjusted for sociodemographics, time trends, nitrogen dioxide, and temperature. To facilitate implementation, we provide a detailed description of the procedure and accompanying R syntax. RESULTS: There were 762 (8.1%) PTBs in this cohort. The gestational week-specific median [PM.sub.2.5] concentration was relatively stable across pregnancy at ~7[micro]g/[m.sup.3]. We found that our hypothetical intervention strategy changed the cumulative risk of PTB at week 36 (i.e., the end of the preterm period) by -0.009 (95% confidence interval: -0.034, 0.007) in comparison with the scenario had we not intervened, which translates to about 86 fewer PTBs in this cohort. We also observed that the critical exposure window appeared to be weeks 5-20. DISCUSSION: We demonstrate that our g-survival-DLM approach produces easier-to-interpret, policy-relevant estimates (due to the g-computation); prevents immortal time bias (due to treating PTB as a time-to-event outcome); and allows for the exploration of critical exposure windows (due to the DLMs). In our illustrative example, we found that reducing fine particulate matter [particulate matter (PM) with aerodynamic diameter, Introduction Pregnant individuals and their fetuses are particularly susceptible to environmental pollutants. (1) Yet, identifying whether environmental exposures cause preterm birth (PTB)--for which the long-term sequelae have been well established [...]

Objective: To evaluate the associations of plasma polybrominated diphenyl ether (PBDE) concentrations in early pregnancy with gestational weight gain (GWG). Design: Prospective cohort study. Setting: US‐based, multicentre cohort of pregnant women. Population: We used data from 2052 women without obesity and 397 women with obesity participating in the NICHD Fetal Growth Studies – Singleton Cohort, with first‐trimester plasma PBDE concentrations and weight measurements throughout pregnancy. Methods: We applied generalised linear models and Bayesian kernel machine regression (BKMR) to evaluate both the individual and joint associations of PBDEs with measures of GWG, adjusting for potential confounders. Main outcome measures: Total GWG (kg), total and trimester‐specific GWG velocities (kg/week), and GWG categories and trajectory groups. Results: Mean pre‐pregnancy BMIs were 23.6 and 34.5 kg/m2 for women without and with obesity, respectively. Among women without obesity, there were no associations of PBDEs with any GWG measure. Among women with obesity, one standard deviation increase in log‐transformed PBDE 47 was associated with a 1.87 kg higher total GWG (95% CI 0.39–3.35) and a 0.05 kg/week higher total GWG velocity (95% CI 0.01–0.09). Similar associations were found for PBDE 47 in BKMR among women with obesity, and PBDE 47, 99 and 100 were associated with lower odds of being in the low GWG trajectory group. Conclusions: PBDEs were not associated with GWG among individuals without obesity. Among those with obesity, only PBDE 47 showed consistent positive associations with GWG measures across multiple statistical methods. Further research is needed to validate this association and explore potential mechanisms. [ABSTRACT FROM AUTHOR]

Objectives Lead exposure has devastating neurologic consequences for children and may begin in utero. The American College of Obstetricians and Gynecologists recommends prenatal lead screening using a risk factor-based approach rather than universal blood testing. The clinical utility of this approach has not been studied. We evaluated a risk-factor based questionnaire to detect elevated blood lead levels in pregnancy. Methods We performed a secondary analysis of a cohort of parturients enrolled to evaluate the association of lead with hypertensive disorders of pregnancy. We included participants in this analysis if they had a singleton pregnancy [greater than or equal to] 34 weeks' gestation with blood lead levels recorded. Participants completed a lead risk factor survey modified for pregnancy. We defined elevated blood lead as [greater than or equal to] 2 [mu]g/dL, as this was the clinically reportable level. Results Of 102 participants enrolled in the cohort, 92 had blood lead measured as part of the study. The vast majority (78%) had 1 or more risk factor for elevated lead using the questionnaire yet none had clinical blood lead testing during routine visits. Only two participants (2.2%) had elevated blood lead levels. The questionnaire had high sensitivity but poor specificity for predicting detectable lead levels (sensitivity 100%, specificity 22%). Conclusions for Practice Prenatal risk-factor based lead screening appears underutilized in practice and does not adequately discriminate between those with and without elevated blood levels. Given the complexity of the risk factor-based approach and underutilization, the benefit and cost-effectiveness of universal lead testing should be further explored., Author(s): Katherine M. Johnson [sup.1] [sup.2] [sup.9] , Aaron J. Specht [sup.3] , Jessica M. Hart [sup.1] [sup.2] , Saira Salahuddin [sup.2] [sup.4] , Adrienne L. Erlinger [sup.1] , Michele [...]

Objectives While some medical indications for cesarean delivery are clear, subjective provider and patient factors contribute to the rising cesarean delivery rates and marked disparities between racial/ethnic groups. We aimed to determine the association between language preference and risk of primary cesarean delivery. Methods We conducted a retrospective cohort study of nulliparous, term, singleton, vertex (NTSV) deliveries of patients over 18 years old from 2011-2016 at an academic medical center, supplemented with data from the Massachusetts Department of Public Health. We used modified Poisson regression with robust error variance to calculate risk ratios for cesarean delivery between patients with English language preference and other language preference, with secondary outcomes of Apgar score, maternal readmission, blood transfusion, and NICU admission. Results Of the 11,298 patients included, 10.3% reported a preferred language other than English, including Mandarin and Cantonese (61.7%), Portuguese (9.7%), and Spanish (7.5%). The adjusted risk ratio for cesarean delivery among patients with a language preference other than English was 0.85 (95% CI 0.72-0.997; p = 0.046) compared to patients with English language preference. No significant differences in risk of secondary outcomes between English and other language preference were found. Discussion After adjusting for confounders, this analysis demonstrates a decreased risk of cesarean delivery among women who do not have an English language preference at one institution. This disparity in cesarean delivery rates in an NTSV population warrants future research, raising the question of what clinical and social factors may be contributing to these lower cesarean delivery rates., Author(s): Kimberly M. Schaefer [sup.1] , Anna M. Modest [sup.1] [sup.2] , Michele R. Hacker [sup.1] [sup.2] , Lucy Chie [sup.1] [sup.2] , Yamicia Connor [sup.1] [sup.2] , Toni Golen [...]

Objectives Most studies examining psychosocial factors contributing to preterm birth (PTB) have focused on negative life events. Studies examining the influence of negative emotion, in particular maternal anger, remain sparse. We examined associations of maternal trait anger expression and lifetime traumatic and non-traumatic experiences with the risk of PTB. Methods Mother-newborn pairs were enrolled in the PRogramming of Intergenerational Stress Mechanisms pregnancy cohort based in Boston and New York City. Women completed the State-Trait Anger Expression Inventory-2 (STAXI-2), Life Stressor Checklist-Revised (LSC-R), and Childhood Trauma Questionnaire (CTQ) in pregnancy. We used modified Poisson regression to estimate the relative risk (RR) of PTB (1) in relation to continuous STAXI-2 Anger Expression-In (AX-I) and Anger Expression-Out (AX-O) subscales, (2) in relation to continuous LSC-R scores, and (3) between women who did versus did not experience childhood sexual, emotional, and/or physical abuse in six separate models. We also examined interactions between maternal anger expression and lifetime stress/childhood trauma. Results Younger, single, minority women had higher outward anger expression and inward anger suppression. AX-I and AX-O scores were higher among women who experienced abuse in childhood and who had higher lifetime stress. Maternal lifetime stress, outward anger expression, and inward anger suppression were associated with an increased risk of PTB in separate models; however, stress, trauma and anger did not interact to further increase the risk of PTB. Conclusions for Practice Higher anger expression and higher lifetime stress experiences were associated with an increased risk of PTB among a racially and ethnically diverse sample of pregnant women., Author(s): Whitney Cowell [sup.1] , Lilly Taing [sup.2] , Talia Askowitz [sup.3] , Michelle Bosquet Enlow [sup.4] [sup.5] , Michele R. Hacker [sup.6] [sup.7] [sup.8] , Rosalind J. Wright [sup.1] [...]

Objective The primary objective was to determine if vaginal progesterone following cerclage for cervical length <10 mm or cervical dilation in patients without a history of spontaneous preterm birth (sPTB) decreased the risk of preterm birth at <34 weeks' gestation compared with cerclage alone. Secondary objectives were to determine if vaginal progesterone following cerclage (1) decreased the risk of preterm birth at <24, <28, and <37 weeks' gestation and (2) increased the latency period from cerclage placement to delivery compared with treatment with cerclage alone. Study Design Multicenter retrospective cohort study from 2015 to 2020 of singleton pregnancies, without prior sPTB, who had cerclage placement <24 weeks' gestation for cervical length <10 mm or cervical dilation. Exposure defined as cerclage plus vaginal progesterone postoperatively (dual therapy) and unexposed as cerclage alone (monotherapy), based on surgeon preference. Results We included 122 patients, 78 (64%) treated with dual therapy and 44 (36%) treated with monotherapy. In the crude analysis, dual therapy was associated with a lower risk of delivery at <28 weeks' gestation (13%) compared with monotherapy (34%; crude risk ratio: 0.38 [95% confidence interval (CI): 0.19–0.75]). When adjusted for preoperative vaginal progesterone, results were attenuated (adjusted risk ratio: 0.45 [95% CI: 0.20–1.01]). In both the crude and adjusted analyses, the risk of sPTB was not statistically different at <24, <34 or <37 weeks' gestation. Dual therapy was associated with a greater pregnancy latency from cerclage to delivery (16.3 vs. 14.4 weeks; p = 0.04), and greater gestational age at delivery (37.3 vs. 35.8 weeks' gestation; p = 0.02) compared with monotherapy. Conclusion While not statistically significant, the risk of sPTB was lower at all gestational ages studied in patients treated with dual therapy compared with monotherapy. Dual therapy was associated with longer pregnancy latency and greater gestational age at delivery compared with monotherapy. Key Points Dual therapy did not decrease preterm birth risk compared with monotherapy. Dual therapy prolonged pregnancy compared with monotherapy. Dual therapy can be considered but further studies are needed. [ABSTRACT FROM AUTHOR]

BACKGROUND: Parametric g-computation is an attractive analytic framework to study the health effects of air pollution. Yet, the ability to explore biologically relevant exposure windows within this framework is underdeveloped. OBJECTIVES: We outline a novel framework for how to incorporate complex lag-responses using distributed lag models (DLMs) into parametric g-computation analyses for survival data. We call this approach “g-survival-DLM” and illustrate its use examining the association between PM2.5 during pregnancy and the risk of preterm birth (PTB). METHODS: We applied the g-survival-DLM approach to estimate the hypothetical static intervention of reducing average PM2.5 in each gestational week by 20% on the risk of PTB among 9,403 deliveries from Beth Israel Deaconess Medical Center, Boston, Massachusetts, 2011–2016. Daily PM2.5 was taken from a 1-km grid model and assigned to address at birth. Models were adjusted for sociodemographics, time trends, nitrogen dioxide, and temperature. To facilitate implementation, we provide a detailed description of the procedure and accompanying R syntax. RESULTS: There were 762 (8.1%) PTBs in this cohort. The gestational week-specific median PM2.5concentration was relatively stable across pregnancy at ~7μg/m³. We found that our hypothetical intervention strategy changed the cumulative risk of PTB at week 36 (i.e., the end of the preterm period) by -0.009 (95% confidence interval: -0.034, 0.007) in comparison with the scenario had we not intervened, which translates to about 86 fewer PTBs in this cohort. We also observed that the critical exposure window appeared to be weeks 5–20. DISCUSSION: We demonstrate that our g-survival-DLM approach produces easier-to-interpret, policy-relevant estimates (due to the g-computation); prevents immortal time bias (due to treating PTB as a time-to-event outcome); and allows for the exploration of critical exposure windows (due to the DLMs). In our illustrative example, we found that reducing fine particulate matter [particulate matter (PM) with aerodynamic diameter ≤2.5 μm (PM2.5)] during gestational weeks 5-20 could potentially lower the risk of PTB. [ABSTRACT FROM AUTHOR]