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PURPOSE: Studies suggest exposure to ambient particulate matter less than 2.5 μg/m(3) in aerodynamic diameter (PM(2.5)) may be associated with preterm birth (PTB), but few have evaluated how this is modified by ambient temperature. We investigated the relationship between PM(2.5) exposure during pregnancy and PTB in infants without birth defects (1999–2006) and enrolled in the National Birth Defects Prevention Study and how it is modified by concurrent temperature. METHODS: PTB was defined as spontaneous or iatrogenic delivery before 37 weeks. Exposure was assigned using inverse distance weighting with up to four monitors within 50 kilometers of maternal residence. To account for state-level variations, a Bayesian two-level hierarchal model was developed. RESULTS: PTB was associated with PM(2.5) during the third and fourth months of pregnancy (range: (odds ratio (95% confidence interval) = 1.00 (0.35, 2.15) to 1.49 (0.82, 2.68) and 1.31 (0.56, 2.91) to 1.62 (0.7, 3.32), respectively); no week of exposure conveyed greater risk. Temperature may modify this relationship; higher local average temperatures during pregnancy yielded stronger positive relationships between PM(2.5) and PTB compared to nonstratified results. CONCLUSIONS: Results add to literature on associations between PM(2.5) and PTB, underscoring the importance of considering co-exposures when estimating effects of PM(2.5) exposure during pregnancy.

Purpose The purpose of this study was to estimate the effect of cigarette smoking and electronic nicotine delivery systems (ENDS) use during pregnancy on small for gestational age (SGA). Methods We used data from the 2016-2017 Arkansas Pregnancy Risk Assessment Monitoring System, estimated the risk ratio (RR) for SGA for maternal prenatal cigarette smoking–only use, cigarette smoking, and ENDS use (i.e., dual use), with no prenatal tobacco use as referent, accounting for the complex survey design. We also explored these effects for women who stopped smoking cigarettes during pregnancy among cigarette smokers and dual users. Results Estimated adjusted RR for SGA for cigarette-only users was 1.7 (95% confidence interval [CI]: 1.1, 2.7), and 1.8 (95% CI: 1.0, 3.4) for dual users. These RR estimates increased after correcting for tobacco use misclassification. Women who were dual users (cigarette smokers and ENDS users) and continued using ENDS but stopped smoking cigarettes had an increased risk for SGA compared with nontobacco users, 3.2 (95% CI: 1.5, 6.6). Conclusions Our results in a population representative sample are consistent with the hypothesis that exposure to both maternal cigarette smoking and ENDS use increased the risk of SGA. Dual users still had an elevated risk of SGA after smoking cessation.

Purpose Studies suggest exposure to ambient particulate matter less than 2.5 μg/m3 in aerodynamic diameter (PM2.5) may be associated with preterm birth (PTB), but few have evaluated how this is modified by ambient temperature. We investigated the relationship between PM2.5 exposure during pregnancy and PTB in infants without birth defects (1999–2006) and enrolled in the National Birth Defects Prevention Study and how it is modified by concurrent temperature. Methods PTB was defined as spontaneous or iatrogenic delivery before 37 weeks. Exposure was assigned using inverse distance weighting with up to four monitors within 50 kilometers of maternal residence. To account for state-level variations, a Bayesian two-level hierarchal model was developed. Results PTB was associated with PM2.5 during the third and fourth months of pregnancy (range: (odds ratio (95% confidence interval) = 1.00 (0.35, 2.15) to 1.49 (0.82, 2.68) and 1.31 (0.56, 2.91) to 1.62 (0.7, 3.32), respectively); no week of exposure conveyed greater risk. Temperature may modify this relationship; higher local average temperatures during pregnancy yielded stronger positive relationships between PM2.5 and PTB compared to nonstratified results. Conclusions Results add to literature on associations between PM2.5 and PTB, underscoring the importance of considering co-exposures when estimating effects of PM2.5 exposure during pregnancy.

PURPOSE: Congenital heart defects (CHDs) are the most prevalent birth defects. Infants with CHDs more often are small-for-gestational age (SGA) than infants without CHD; however, little is known about racial/ethnic variations in prevalence of SGA or large-for-gestational age (LGA) for infants born with CHDs. This study determined the risk of SGA and LGA for non-Hispanic (NH)-black and Hispanic infants with CHDs. METHODS: Data from the Florida Birth Defects Registry were used in a retrospective cohort study of 10,027 live-born infants to resident NH-White, NH-Black, and Hispanic women ages 15-49 years from January 1, 1998, to December 31, 2003, and diagnosed with 11 CHDs. Defect-specific odds ratios and 95% confidence intervals were computed for risk of SGA and LGA by race/ethnicity and adjusted for covariates using multinomial logistic regression. RESULTS: After adjusting for covariates, we found there were no statistically significant racial/ethnic differences in risk of SGA. However, NH-Blacks with ventricular septal defect had increased risk of LGA and NH-Blacks with tetralogy of Fallot had decreased risk of LGA compared to NH-Whites. CONCLUSIONS: Very few racial/ethnic differences in fetal growth are present among infants with CHD. Further elucidation of the factors involved in fetal growth and the impact of CHD itself on fetal development is needed.