Most of the women who smoke before pregnancy continue smoking during pregnancy, and some start to quit smoking after being pregnant, although existing guidelines for pregnancy recommend that women who smoke should quit smoking before pregnancy. Findings about the timing and intensity of maternal smoking, especially low-intensity smoking (1–9 cigarettes per day), and preterm birth are still inconsistent and ambiguous. This study aimed to examine the association of the timing of smoking and doses of smoking before pregnancy and during the first or second trimester of pregnancy with preterm birth in a large-scale population-based retrospective cohort study. We used nationwide birth certificate data from singleton mother–infant pairs in the United States National Vital Statistics System, 2011–2018. All adult women with live singleton births, without preexisting hypertension or diabetes, and with complete data on smoking and gestational age at delivery were included. Participants reported their smoking status (yes or no) and daily number of cigarettes consumed before and during each trimester of pregnancy. The outcome of interest was preterm birth, defined as a birth before 37 weeks of gestation. Logistic regression models were used to estimate the odds ratio (OR) with 95% confidence intervals (CIs) of preterm birth associated with smoking status and the number of cigarettes consumed, adjusting for maternal age, race/ethnicity, parity, education levels, prepregnancy BMI, previous history of preterm birth, marital status, infant sex, and initiation of prenatal care. This study included 25,623,479 women, with a mean age of 29 years (range 20–50 years); 13,742,486 (53.6%) participants were of non-Hispanic white ancestry, 5,971,598 (23.3%) of Hispanic ancestry, and 3,417,456 (13.34%) of non-Hispanic black ancestry. The prevalence of preterm birth was 9.3% (n = 2,378,398). We found that maternal smoking during pregnancy, even at a very low level of intensity, was associated with an increased risk of preterm delivery. The adjusted ORs (95% CI) of preterm birth for mothers who smoked 1–2, 3–5, 6–9, 10–19, and ≥20 cigarettes per day during the first trimester compared with mothers who did not smoke were 1.31 (1.29–1.33), 1.31 (1.30–1.32), 1.33 (1.31–1.35), 1.44 (1.43–1.45), and 1.53 (1.52–1.55), respectively (all P values < 0.001), whereas for those who smoked during the second trimester, the corresponding ORs were 1.37 (1.35–1.39), 1.36 (1.35–1.38), 1.36 (1.34–1.38), 1.48 (1.47–1.49), and 1.59 (1.58–1.61), respectively (all P values < 0.001). Furthermore, smokers who quit before pregnancy, regardless of smoking intensity, had a comparable risk of preterm birth with nonsmokers, although this was not the case when cessation occurred in the first or second trimester of pregnancy. The major limitation of this study is the self-reported information about smoking, which may be subject to information bias. In addition, we cannot rule out the possibility of residual confounding caused by unmeasured factors in an observational research design. In this study, we observed that low-intensity cigarette consumption during either the first or second trimester of pregnancy, even as low as 1–2 cigarettes per day, was associated with an increased risk of preterm birth. These findings suggest that there is no safe level or safe trimester for maternal smoking during pregnancy. Women of reproductive age who smoke should be strongly encouraged and supported to quit smoking before pregnancy.

Background: The organic food market has grown rapidly worldwide in the past 15 years. However, evidence concerning the health effects of organic foods is scarce. We evaluated the cross-sectional association of organic food purchase, as a proxy of organic food consumption, with diabetes in a nationally representative population. Methods: We included 8199 participants aged ≥20 years from the National Health and Nutrition Examination Survey 2007–2008 and 2009–2010. Organic food purchase and frequency were ascertained by questionnaires. Diabetes was defined as a self-reported physician diagnosis or a hemoglobin A1c level ≥6.5% or both. We used logistic regression with sample weights to estimate the odds ratios (ORs) and 95% confidence intervals (CIs). Results: Individuals who reported purchasing organic foods were less likely to have diabetes compared to those who did not report organic food purchase. After adjustment for age, gender, race/ethnicity, family history of diabetes, socioeconomic status, and dietary and lifestyle factors, the OR of diabetes associated with organic food purchase was 0.80 (95% CI 0.68–0.93). The association remained significant after additional adjustment for BMI with OR of 0.80 (0.69–0.94). Conclusions: In a nationally representative population, frequent organic food purchase was inversely associated with diabetes prevalence in adults in the United States.

Background: Previous studies have predominately examined associations of respiratory allergy and skin allergy with ADHD, but little is known about the association between food allergy and ADHD. Methods: We included 192,573 children aged 4–17 years from the National Health Interview Survey (NHIS), a leading health survey in a nationally representative sample of the US population. Allergy conditions and ADHD were defined based on an affirmative response in the NHIS questionnaire. We used weighted logistic regression to estimate the odds ratio (OR) of ADHD. Results: Among the 192,573 children, 15,376 reported ADHD diagnosis. The prevalence of ADHD was higher among children with allergic conditions: 12.66% vs. 7.99% among children with and without food allergy; 12.16% vs. 7.63% among children with and without respiratory allergy; and 11.46% vs. 7.83% among children with and without skin allergy. After adjusting for covariates, the OR of ADHD was 1.72 (95% CI, 1.55–1.91) comparing children with and without food allergy, 1.50 (95% CI, 1.41–1.59) comparing children with and without respiratory allergy, and 1.65 (95% CI, 1.55–1.75) comparing children with and without skin allergy. The observed associations remained significant after mutual adjustment for other allergic conditions. Conclusions: In a nationally representative sample of US children, we found a significant association of common allergic conditions (food allergy, respiratory allergy, and skin allergy) with ADHD.

Polybrominated diphenyl ethers (PBDEs) are a group of persistent organic pollutants that represent a substantial environmental and human health concern.^1,2 Since the 1970s, PBDEs have been used as flame retardants in a wide array of consumer products, such as building materials, furnishings, and electronics.³ PBDEs enter the environment at sites of production, use, and disposal of PBDE-containing products. PBDEs strongly bind to sediments and soils because of their low water solubility and high lipophilicity.⁴ They degrade in the environment by debromination reactions, forming more toxic, lower brominated PBDE congeners.