Pregnancy Planning and its Association with Autism Spectrum Disorder: Findings from the Study to Explore Early Development.

OBJECTIVES: To examine associations between pregnancy planning and autism spectrum disorder (ASD) in offspring. METHODS: The Study to Explore Early Development (SEED), a multi-site case-control study, enrolled preschool-aged children with ASD, other DDs, and from the general population (POP). Some children with DDs had ASD symptoms but did not meet the ASD case definition. We examined associations between mother's report of trying to get pregnant (pregnancy planning) and (1) ASD and (2) ASD symptomatology (ASD group, plus DD with ASD symptoms group combined) (each vs. POP group). We computed odds ratios adjusted for demographic, maternal, health, and perinatal health factors (aORs) via logistic regression. Due to differential associations by race-ethnicity, final analyses were stratified by race-ethnicity. RESULTS: Pregnancy planning was reported by 66.4%, 64.8%, and 76.6% of non-Hispanic White (NHW) mothers in the ASD, ASD symptomatology, and POP groups, respectively. Among NHW mother-child pairs, pregnancy planning was inversely associated with ASD (aOR = 0.71 [95% confidence interval 0.56-0.91]) and ASD symptomatology (aOR = 0.67 [0.54-0.84]). Pregnancy planning was much less common among non-Hispanic Black mothers (28-32% depending on study group) and Hispanic mothers (49-56%) and was not associated with ASD or ASD symptomatology in these two race-ethnicity groups. CONCLUSION: Pregnancy planning was inversely associated with ASD and ASD symptomatology in NHW mother-child pairs. The findings were not explained by several adverse maternal or perinatal health factors. The associations observed in NHW mother-child pairs did not extend to other race-ethnicity groups, for whom pregnancy planning was lower overall.

Prenatal ultrasound use and risk of autism spectrum disorder: Findings from the case-control Study to Explore Early Development.

BACKGROUND: Studies evaluating the association between prenatal ultrasounds and autism spectrum disorder (ASD) have largely produced negative results. Concern remains due to the rising identification of children with ASD and ultrasound use. OBJECTIVE: To evaluate the association between prenatal ultrasound use and ASD. METHODS: We used data from the Study to Explore Early Development, a multisite case-control study of preschool-aged children with ASD implemented during 2007-2012. We recruited cases from children receiving developmental disability services and randomly selected population controls from birth records. ASD case status was based on in-person standardised assessments. We stratified analyses by pre-existing maternal medical conditions and pregnancy complications associated with increased ultrasound use (ultrasound indications) and used logistic regression to model case status by increasing ultrasound counts. For pregnancies with medical record data on ultrasound timing, we conducted supplementary tests to model associations by trimester of exposure. RESULTS: Among 1524 singleton pregnancies, ultrasound indications were more common for ASD cases than controls; respectively, for each group, no indications were reported for 45.1% and 54.2% of pregnancies, while ≥2 indications were reported for 26.1% and 18.4% of pregnancies. The percentage of pregnancies with multiple ultrasounds varied by case status and the presence of ultrasound indications. However, stratified regression models showed no association between increasing ultrasound counts and case status, either for pregnancies without (aOR 1.01, 95% CI 0.92, 1.11) or with ultrasound indications (aOR 1.01, 95% CI 0.95, 1.08). Trimester-specific analyses using medical record data showed no association in any individual trimester. CONCLUSIONS: We found no evidence that prenatal ultrasound use increases ASD risk. Study strengths included gold-standard assessments for ASD case classification, comparison of cases with controls, and a stratified sample to account for conditions associated both with increased prenatal ultrasound use and ASD.

Reasons for participation in a child development study: Are cases with developmental diagnoses different from controls?

BACKGROUND: Current knowledge about parental reasons for allowing child participation in research comes mainly from clinical trials. Fewer data exist on parents' motivations to enrol children in observational studies. OBJECTIVES: Describe reasons parents of preschoolers gave for participating in the Study to Explore Early Development (SEED), a US multi-site study of autism spectrum disorder (ASD) and other developmental delays or disorders (DD), and explore reasons given by child diagnostic and behavioural characteristics at enrolment. METHODS: We included families of children, age 2-5 years, participating in SEED (n = 5696) during 2007-2016. We assigned children to groups based on characteristics at enrolment: previously diagnosed ASD; suspected ASD; non-ASD DD; and population controls (POP). During a study interview, we asked parents their reasons for participating. Two coders independently coded responses and resolved discrepancies via consensus. We fit binary mixed-effects models to evaluate associations of each reason with group and demographics, using POP as reference. RESULTS: Participants gave 1-5 reasons for participation (mean = 1.7, SD = 0.7). Altruism (48.3%), ASD research interest (47.4%) and perceived personal benefit (26.9%) were most common. Two novel reasons were knowing someone outside the household with the study conditions (peripheral relationship; 14.1%) and desire to contribute to a specified result (1.4%). Odds of reporting interest in ASD research were higher among diagnosed ASD participants (odds ratio [OR] 2.89, 95% confidence interval [CI] 2.49-3.35). Perceived personal benefit had higher odds among diagnosed (OR 1.92, 95% CI 1.61-2.29) or suspected ASD (OR 3.67, 95% CI 2.99-4.50) and non-ASD DD (OR 1.80, 95% CI 1.50-2.16) participants. Peripheral relationship with ASD/DD had lower odds among all case groups. CONCLUSIONS: We identified meaningful differences between groups in parent-reported reasons for participation. Differences demonstrate an opportunity for future studies to tailor recruitment materials and increase the perceived benefit for specific prospective participants.

Association Between Midpregnancy Polyunsaturated Fatty Acid Levels and Offspring Autism Spectrum Disorder in a California Population-Based Case-Control Study.

Polyunsaturated fatty acids (PUFAs) are critical for brain development and have been linked with neurodevelopmental outcomes. We conducted a population-based case-control study in California to examine the association between PUFAs measured in midpregnancy serum samples and autism spectrum disorder (ASD) in offspring. ASD cases (n = 499) were identified through the California Department of Developmental Services and matched to live-birth population controls (n = 502) on birth month, year (2010 or 2011), and sex. Logistic regression models were used to examine crude and adjusted associations. In secondary analyses, we examined ASD with and without co-occurring intellectual disability (ID; n = 67 and n = 432, respectively) and effect modification by sex and ethnicity. No clear patterns emerged, though there was a modest inverse association with the top quartile of linoleic acid level (highest quartile vs. lowest: adjusted odds ratio = 0.74, 95% confidence interval: 0.49, 1.11; P for trend = 0.10). Lower levels of total and ω-3 PUFAs were associated with ASD with ID (lowest decile of total PUFAs vs. deciles 4-7: adjusted odds ratio = 2.78, 95% confidence interval: 1.13, 6.82) but not ASD without ID. We did not observe evidence of effect modification by the factors examined. These findings do not suggest a strong association between midpregnancy PUFA levels and ASD. In further work, researchers should consider associations with ASD with ID and in other time windows.

Coccidioidomycosis outbreak among inmate wildland firefighters: California, 2017.

BACKGROUND: In California, state prison inmates are employed to fight wildfires, which involves performing soil-disrupting work. Wildfires have become more common, including areas where Coccidioides, the soil-dwelling fungus that causes coccidioidomycosis, proliferates. However, work practices that place wildland firefighters at risk for coccidioidomycosis have not been investigated. METHODS: On August 17, 2017, the California Department of Public Health was notified of a cluster of coccidioidomycosis cases among Wildfire A inmate wildland firefighters. We collected data through medical record abstraction from suspected case-patients and mailed a survey assessing potential job task risk factors to Wildfire A inmate firefighters. We described respondent characteristics and conducted a retrospective case-control investigation to assess coccidioidomycosis risk factors. RESULTS: Among 198 inmate firefighters who worked on Wildfire A, 112 (57%) completed the survey. Of 10 case-patients (four clinical and six laboratory-confirmed), two were hospitalized. In the case-control analysis of 71 inmate firefighters, frequently cutting fire lines with a McLeod tool (odds ratio [OR]: 5.5; 95% confidence interval [CI]: 1.1-37.2) and being in a dust cloud or storm (OR: 4.3; 95% CI: 1.1-17.4) were associated with illness. Two of 112 inmate firefighters reported receiving coccidioidomycosis training; none reported wearing respiratory protection on this wildfire. CONCLUSIONS: Wildland firefighters who use hand tools and work in dusty conditions where Coccidioides proliferates are at risk for coccidioidomycosis. Agencies that employ them should provide training about coccidioidomycosis and risk reduction, limit dust exposure, and implement respiratory protection programs that specify where respirator use is feasible and appropriate.

Early Life Exposure to Air Pollution and Autism Spectrum Disorder: Findings from a Multisite Case-Control Study.

BACKGROUND: Epidemiologic studies have reported associations between prenatal and early postnatal air pollution exposure and autism spectrum disorder (ASD); however, findings differ by pollutant and developmental window. OBJECTIVES: We examined associations between early life exposure to particulate matter ≤2.5 µm in diameter (PM2.5) and ozone in association with ASD across multiple US regions. METHODS: Our study participants included 674 children with confirmed ASD and 855 population controls from the Study to Explore Early Development, a multi-site case-control study of children born from 2003 to 2006 in the United States. We used a satellite-based model to assign air pollutant exposure averages during several critical periods of neurodevelopment: 3 months before pregnancy; each trimester of pregnancy; the entire pregnancy; and the first year of life. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for study site, maternal age, maternal education, maternal race/ethnicity, maternal smoking, and month and year of birth. RESULTS: The air pollution-ASD associations appeared to vary by exposure time period. Ozone exposure during the third trimester was associated with ASD, with an OR of 1.2 (95% CI: 1.1, 1.4) per 6.6 ppb increase in ozone. We additionally observed a positive association with PM2.5 exposure during the first year of life (OR = 1.3 [95% CI: 1.0, 1.6] per 1.6 µg/m increase in PM2.5). CONCLUSIONS: Our study corroborates previous findings of a positive association between early life air pollution exposure and ASD, and identifies a potential critical window of exposure during the late prenatal and early postnatal periods.

Risk factors for occupational heat-related illness among California workers, 2000-2017.

BACKGROUND: As climate change increases global temperatures, heat-related morbidity and mortality are projected to rise. Outdoor workers and those who perform exertional tasks are particularly susceptible to heat-related illness (HRI). Using workers' compensation data, we aimed to describe rates of occupational HRI in California and identify demographic and occupational risk factors to inform prevention efforts. METHODS: We identified HRI cases during 2000-2017 in the California Workers' Compensation Information System (WCIS) using International Classification of Diseases Ninth and Tenth Revision codes, WCIS nature and cause of injury codes, and HRI keywords. We assigned industry and occupation codes using the NIOSH Industry and Occupation Computerized Coding System (NIOCCS). We calculated HRI rates by sex, age group, year, county, industry, and occupation, and estimated confidence intervals using generalized linear models. RESULTS: We identified 15,996 HRI cases during 2000-2017 (6.0 cases/100,000 workers). Workers aged 16-24 years had the highest HRI rate (7.6) among age groups, and men (8.1) had a higher rate than women (3.5). Industry sectors with the highest HRI rates were Agriculture, Farming, Fishing, and Forestry (38.6), and Public Administration (35.3). Occupational groups with the highest HRI rates were Protective Services (56.6) and Farming, Fishing, and Forestry (36.6). Firefighters had the highest HRI rate (389.6) among individual occupations. CONCLUSIONS: Workers in certain demographic and occupational groups are particularly susceptible to HRI. Additional prevention efforts, including outreach and enforcement targeting high-risk groups, are needed to reduce occupational HRI. Workers' compensation data can provide timely information about temporal trends and risk factors for HRI.

Prenatal Exposure to Endocrine-disrupting Chemicals in Relation to Autism Spectrum Disorder and Intellectual Disability.

BACKGROUND: Exposure to endocrine disruptors is unavoidable. Many such compounds are suspected to impact neurologic development of children, but most studies conducted have considered effects of individual chemicals in isolation. Because exposures co-occur, it is important to consider their health impacts in a single regression framework. METHODS: We applied Bayesian statistical tools (including shared mean and mixture priors for 25 unique chemicals) to study independent associations of endocrine disruptor biomarkers with autism spectrum disorder (ASD) (n = 491) and intellectual disability (n = 155), compared with 373 general population controls, in the Early Markers for Autism study. We measured biomarkers in maternal serum collected and stored from midpregnancy and considered them individually or as a class (i.e., summed polychlorinated biphenyls). We adjusted all models for original matching factors (child sex and month and year of birth), maternal age, maternal race/ethnicity, parity, and maternal education at the time samples were collected. We estimated the change in the odds of ASD or intellectual disability per 1 SD increase in the z-score of measured biomarker concentration for each chemical. RESULTS: Odds of ASD and intellectual disability did not change with increasing concentration for any specific endocrine disruptor. The effect estimates for each chemical were centered on or near an odds ratio of 1.00 in both models where we applied a shared mean or a mixture prior. CONCLUSION: Our mixtures analyses do not suggest an independent relationship with ASD or intellectual disability with any of the 25 chemicals examined together in this mixtures analysis.

Longitudinal study of age of menarche in association with childhood concentrations of persistent organic pollutants.

BACKGROUND: Age at female puberty is associated with adult morbidities, including breast cancer and diabetes. Hormonally active chemicals are suspected of altering pubertal timing. We examined whether persistent organic pollutants (POPs) are associated with age at menarche in a longitudinal study. METHODS: We analyzed data for females enrolled at age 6-8 years in the Breast Cancer and Environment Research Program from California and Ohio. Participants were followed annually 2004-2013 and provided serum (mean age 7.8 years) for measurement of polychlorinated biphenyl (PCB), organochlorine pesticide (OCP), and polybrominated diphenyl ether (PBDE) concentrations. Age of menarche was assigned based on parental and participant reported dates and ages of menarche. Adjusted hazard ratios (aHRs) for menarchal onset were calculated with Cox proportional regression. Body mass index (BMI), potentially on the causal pathway, was added to parallel analyses. RESULTS: Age of menarche was later with higher summed PCB levels (median 11.9 years in quartile 1 [Q1] versus 12.7 in quartile 4 [Q4]) and OCP levels (12.1 years versus 12.4, respectively). When adjusting for all covariates except BMI, higher POP concentrations were associated with later age at menarche (Q4 versus Q1 aHRs: PBDEs 0.75 [95% CI 0.58, 0.97], PCBs 0.67 [95% CI 0.5, 0.89], and OCPs 0.66 [95% CI 0.50, 0.89]). Additional adjustment for BMI attenuated aHRs; PCB aHR approached the null. CONCLUSION: Findings revealed later onset of menarche with higher concentrations of certain POPs, possibly through an association with BMI. Altered pubertal timing may have long lasting effects on reproductive health and disease risk, so continued attention is important for understanding the biological processes affected by hormonally active chemicals.

Demographic and Operational Factors Predicting Study Completion in a Multisite Case-Control Study of Preschool Children.

Participant attrition can limit inferences drawn from study results and inflate research costs. We examined factors associated with completion of the Study to Explore Early Development (2007-2011), a multiple-component, case-control study of risk factors for autism spectrum disorder in preschoolers, conducted in California, Colorado, Georgia, Maryland, North Carolina, and Pennsylvania. Participants (n = 3,769) were asked to complete phone interviews, questionnaires, an in-person evaluation, and biologic sampling. We examined whether participant demographic and administrative factors predicted completion using mixed-effects logistic regression models. Completion of individual key study components was generally 70% or higher. However, 58% of families completed all per-protocol data elements (defined a priori as key study components). Per-protocol completion differed according to mother's age, race, educational level, driving distance to clinic, number of contact attempts to enroll, and number of telephone numbers provided (all P < 0.05). Case status was not associated with completion, despite additional data collection for case-confirmation. Analysis of a subset that completed an early interview revealed no differences in completion by household factors of income, primary language spoken, number of adults, or number of children with chronic conditions. Differences in completion by race and education were notable and need to be carefully considered in developing future recruitment and completion strategies.

Urinary biomarkers of polycyclic aromatic hydrocarbons in pre- and peri-pubertal girls in Northern California: Predictors of exposure and temporal variability.

BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs), a class of chemicals produced as combustion by-products, have been associated with endocrine disruption. To understand exposure in children, who have been less studied than adults, we examined PAH metabolite concentrations by demographic characteristics, potential sources of exposure, and variability over time, in a cohort study of pre- and peri-pubertal girls in Northern California. METHODS: Urinary concentrations of ten PAH metabolites and cotinine were quantified in 431 girls age 6-8 years at baseline. Characteristics obtained from parental interview, physical exam, and linked traffic data were examined as predictors of PAH metabolite concentrations using multivariable linear regression. A subset of girls (n = 100) had repeat measures of PAH metabolites in the second and fourth years of the study. We calculated the intraclass correlation coefficient (ICC), Spearman correlation coefficients, and how well the quartile ranking by a single measurement represented the four-year average PAH biomarker concentration. RESULTS: Eight PAH metabolites were detected in ≥ 95% of the girls. The most consistent predictors of PAH biomarker concentrations were cotinine concentration, grilled food consumption, and region of residence, with some variation by demographics and season. After adjustment, select PAH metabolite concentrations were higher for Hispanic and Asian girls, and lower among black girls; 2-naphthol concentrations were higher in girls from lower income households. Other than 1-naphthol, there was modest reproducibility over time (ICCs between 0.18 and 0.49) and the concentration from a single spot sample was able to reliably rank exposure into quartiles consistent with the multi-year average. CONCLUSIONS: These results confirm diet and environmental tobacco smoke exposure as the main sources of PAHs. Controlling for these sources, differences in concentrations still existed by race for specific PAH metabolites and by income for 2-naphthol. The modest temporal variability implies adequate exposure assignment using concentrations from a single sample to define a multi-year exposure timeframe for epidemiologic exposure-response studies.

Phenol Concentrations During Childhood and Subsequent Measures of Adiposity Among Young Girls.

Phenolic compounds represent a class of environmental chemicals with potentially endocrine-disrupting capabilities. We investigated longitudinal associations between childhood exposure to phenols, from both manmade and natural sources, and subsequent measures of adiposity among girls enrolled in the Breast Cancer and the Environment Research Program between 2004 and 2007. Baseline (ages 6-8 years) urinary concentrations were obtained for creatinine and phenol metabolites: enterolactone, genistein, daidzein, benzophenone-3, bisphenol A, the sum of parabens (methyl, ethyl, and propyl parabens), 2,5-dichlorophenol, and triclosan. Body mass index (weight (kg)/height (m)2), waist circumference, and percent body fat were measured at annual or semiannual examinations through 2015 (n = 1,017). Linear mixed-effects regression was used to estimate how baseline concentrations of phenols (tertile groups) were related to changes in girls' adiposity measurements from ages 7 through 15 years. Enterolactone was inversely associated with body mass index, waist circumference, and percent body fat, while 2,5-dichlorophenol was positively associated with these measurements. A nonmonotonic association was observed for triclosan and girls' adiposity; however, it was due to effect modification by baseline overweight status. Triclosan was positively associated with adiposity only among overweight girls. These results suggest that exposure to specific phenols during childhood may influence adiposity through adolescence.

The Changing Epidemiology of Autism Spectrum Disorders.

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with lifelong impacts. Genetic and environmental factors contribute to ASD etiology, which remains incompletely understood. Research on ASD epidemiology has made significant advances in the past decade. Current prevalence is estimated to be at least 1.5% in developed countries, with recent increases primarily among those without comorbid intellectual disability. Genetic studies have identified a number of rare de novo mutations and gained footing in the areas of polygenic risk, epigenetics, and gene-by-environment interaction. Epidemiologic investigations focused on nongenetic factors have established advanced parental age and preterm birth as ASD risk factors, indicated that prenatal exposure to air pollution and short interpregnancy interval are potential risk factors, and suggested the need for further exploration of certain prenatal nutrients, metabolic conditions, and exposure to endocrine-disrupting chemicals. We discuss future challenges and goals for ASD epidemiology as well as public health implications.

Age at Pubertal Onset in Girls and Tobacco Smoke Exposure During Pre- and Postnatal Susceptibility Windows.

BACKGROUND: Tobacco smoke contains known hormonally active chemicals and reproductive toxicants. Several studies have examined prenatal maternal smoking and offspring age at menarche, but few examined earlier pubertal markers, nor accounted for exposure during childhood. Our objective was to examine pre- and postnatal smoke exposure in relation to timing of early pubertal events. METHODS: An ethnically diverse cohort of 1239 girls was enrolled at age 6-8 years old for a longitudinal study of puberty at three US sites. Girls participated in annual or semi-annual exams to measure anthropometry and Tanner breast and pubic hair stages. Prenatal and current tobacco smoke exposures, as well as covariates, were obtained from parent questionnaire. Cotinine was measured in urine collected at enrollment. Using accelerated failure time models, we calculated adjusted time ratios for age at pubertal onset (maturation stages 2 or higher) and smoke exposure. RESULTS: Girls with higher prenatal (≥5 cigarettes per day) or secondhand smoke exposure had earlier pubic hair development than unexposed (adjusted time ratio: 0.92 [95% CI = 0.87, 0.97] and 0.94 [95% CI = 0.90, 0.97], respectively). Including both exposures in the same model yielded similar associations. Higher urinary cotinine quartiles were associated with younger age at breast and pubic hair onset in unadjusted models, but not after adjustment. CONCLUSIONS: Greater prenatal and childhood secondhand smoke exposure were associated with earlier onset of pubic hair, but not breast, development. These exposures represent modifiable risk factors for early pubertal development that should be considered for addition to the extensive list of adverse effects from tobacco smoke.

Peripubertal dietary flavonol and lignan intake and age at menarche in a longitudinal cohort of girls.

BackgroundDietary phytoestrogens may alter hormonal activity in childhood. Flavonols and lignans are the most prevalent phytoestrogens in the Western diet. We examined whether higher intake of flavonols and lignans was associated with later age at menarche in a prospective study of young girls.MethodsIn all, 1,044 girls aged 6-8 years (mean 7.3 years) with two to four 24-h dietary recalls during their baseline year were followed up for 11 years until the attainment of menarche in the Breast Cancer and Environment Research Project (BCERP). Associations of age at menarche with quintiles of phytoestrogens were assessed using hazard ratios (HR) and 95% confidence intervals (CIs) from Cox proportional hazards models, controlling for body mass index and other covariates.ResultsThe highest quintile of flavonol intake was associated with a later age at menarche, compared with the lowest quintile (adjusted HR: 0.80, 95% CI: (0.66-1.00). For lignans, there was a later age in overweight girls (HR: 0.56, 95% CI=0.40-0.80).ConclusionThese dietary bioactives may reflect a healthy diet, and foods high in phytoestrogens may influence the timing of menarche.

Prenatal Alcohol Exposure in Relation to Autism Spectrum Disorder: Findings from the Study to Explore Early Development (SEED).

BACKGROUND: Prenatal alcohol exposure can affect neurodevelopment, but few studies have examined associations with autism spectrum disorder (ASD). METHODS: We assessed the association between maternal alcohol use and ASD in the Study to Explore Early Development, a multi-site case-control study of children born between September 2003 and August 2006 in the US Regression analyses included 684 children with research clinician-confirmed ASD, 869 children with non-ASD developmental delays or disorders (DDs), and 962 controls ascertained from the general population (POP). Maternal alcohol exposure during each month from 3 months prior to conception until delivery was assessed by self-report. RESULTS: Mothers of POP children were more likely to report any prenatal alcohol use than mothers of children with ASD or DD. In trimester one, 21.2% of mothers of POP children reported alcohol use compared with 18.1% and 18.2% of mothers of children with ASD or DD, respectively (adjusted OR for ASD vs. POP 0.8, 95% confidence interval 0.6, 1.1). During preconception and the first month of pregnancy, one to two drinks on average per week was inversely associated with ASD risk. CONCLUSIONS: These results do not support an adverse association between low-level alcohol exposure and ASD, although these findings were based on retrospective self-reported alcohol use. Unmeasured confounding or exposure misclassification may explain inverse associations with one to two drinks per week. Pregnant or potentially pregnant women should continue to follow recommendations to avoid alcohol use because of other known effects on infant health and neurodevelopment.

Associations Between Maternal Pregravid Obesity and Gestational Diabetes and the Timing of Pubarche in Daughters.

We investigated whether in utero exposure to maternal pregravid obesity and/or gestational diabetes mellitus (GDM) was associated with early puberty in girls. We used data from a longitudinal study of 421 mother-daughter pairs enrolled in an integrated health services organization, Kaiser Permanente Northern California (2005-2012). Girls aged 6-8 years were followed annually through ages 12-14 years. Onset of puberty was assessed using study clinic-based Tanner staging. We examined associations of self-reported pregravid obesity and maternal GDM with timing of the daughter's transition to pubertal maturation stage 2 or above for development of breasts and pubic hair, using accelerated failure time regression models with interval censoring to estimate time ratios and hazard ratios and corresponding 95% confidence intervals. Maternal obesity (pregravid body mass index (BMI; weight (kg)/height (m)(2)) ≥30) was associated with a daughter's earlier transition to breast and pubic hair stage 2+ in comparison with girls whose mothers had pregravid BMI <25. These associations were attenuated and not statistically significant after adjustment for covariates. Girls whose mothers had both pregravid BMI ≥25 and GDM were at higher risk of an earlier transition to pubic hair stage 2+ than those whose mothers had neither condition (adjusted time ratio = 0.89, 95% confidence interval: 0.83, 0.96; hazard ratio = 2.97, 95% confidence interval: 1.52, 5.83). These findings suggest that exposure to maternal obesity and hyperglycemia places girls at higher risk of earlier pubarche.

Longitudinal Associations of Phthalate Exposures During Childhood and Body Size Measurements in Young Girls.

BACKGROUND: Phthalates are environmental chemicals that may play a role in the development of obesity. Few studies have investigated longitudinal associations between postnatal phthalate exposures and subsequent anthropometric measurements in children. METHODS: We collected data as part of The Breast Cancer and Environment Research Program at three US sites. A total of 1,239 girls, aged 6-8 years, were enrolled in 2004-2007. We categorized baseline phthalate exposures, assessed from creatinine-corrected urinary concentrations of low-molecular weight phthalate metabolites, as low, <78; medium, 78 to <194; and high, ≥194 µg/g creatinine and of high-molecular weight phthalates as low, <111; medium, 111-278; and high, ≥278 µg/g creatinine. Anthropometric measurements were collected through 2012 (n = 1,017). Linear mixed effects regression estimated how baseline low and high-molecular weight phthalate concentrations related to changes in girls' body mass index (BMI), height, and waist circumference at ages 7-13 years. RESULTS: Low-molecular weight phthalates were positively associated with gains in BMI and waist circumference. Predicted differences in BMI and waist circumference between girls with high versus low concentrations of low-molecular weight phthalates increased from 0.56 (95% confidence interval [CI]: -0.02, 1.1) to 1.2 kg/m (95% CI: 0.28, 2.1) and from 1.5 (95% CI: -0.38, 3.3) to 3.9 cm (95% CI: 1.3, 6.5), respectively. High-molecular weight phthalates were negatively associated with height but only among girls who were normal weight at baseline (BMI ≤ 85th percentile). CONCLUSION: Phthalates, specifically low-molecular weight phthalates, have small but detectable associations with girls' anthropometric outcomes. Low-molecular weight phthalates showed stronger associations than other types of phthalates.

Thyroid Hormones and Timing of Pubertal Onset in a Longitudinal Cohort of Females, Northern California, 2006-11.

BACKGROUND: Pubertal timing is regulated by a complex interplay of hormones. Few studies have evaluated the role of thyroid hormones in pubertal onset. We investigated the associations between blood concentrations of free and total thyroxine (FT4, TT4), free triiodothyronine, and thyroid stimulating hormone and pubertal onset among females. METHODS: Participants included 323 Kaiser Permanente Northern California members followed at annual intervals during 2004-11, who provided a blood sample during the first 3 years of the study. Thyroid hormone concentrations were measured in serum in the first blood specimen available for each participant. Pubertal onset was defined as Tanner stage ≥2 for breast (thelarche) and pubic hair (pubarche) development. Associations between thyroid hormones and pubertal onset were assessed by multivariable logistic regression and Cox proportional hazards modelling. RESULTS: At blood draw, participants were age 6.5-10.1 (median 7.7) years, 10% had reached thelarche, and 12% had reached pubarche. Participants were followed 0-5 years after blood draw (median 4). At most recent clinical visit, participants were age 6.7-14.7 (median 12.3) years, 92% had reached thelarche, and 89% had reached pubarche. No associations were identified between having reached thelarche or pubarche at time of blood draw and thyroid hormones. Examined longitudinally, higher concentrations of pre-pubertal FT4 and TT4 were associated with earlier pubarche (adjusted hazard ratio (HR) 1.41, 95% confidence interval (CI) 1.06, 1.86; per ng/dL and aHR 1.07, 95% CI 1.02, 1.12; per µg/dL respectively). CONCLUSIONS: Higher pre-pubertal concentrations of FT4 and TT4 are associated with earlier pubarche.

Presence of an epigenetic signature of prenatal cigarette smoke exposure in childhood.

Prenatal exposure to tobacco smoke has lifelong health consequences. Epigenetic signatures such as differences in DNA methylation (DNAm) may be a biomarker of exposure and, further, might have functional significance for how in utero tobacco exposure may influence disease risk. Differences in infant DNAm associated with maternal smoking during pregnancy have been identified. Here we assessed whether these infant DNAm patterns are detectible in early childhood, whether they are specific to smoking, and whether childhood DNAm can classify prenatal smoke exposure status. Using the Infinium 450K array, we measured methylation at 26 CpG loci that were previously associated with prenatal smoking in infant cord blood from 572 children, aged 3-5, with differing prenatal exposure to cigarette smoke in the Study to Explore Early Development (SEED). Striking concordance was found between the pattern of prenatal smoking associated DNAm among preschool aged children in SEED and those observed at birth in other studies. These DNAm changes appear to be tobacco-specific. Support vector machine classification models and 10-fold cross-validation were applied to show classification accuracy for childhood DNAm at these 26 sites as a biomarker of prenatal smoking exposure. Classification models showed prenatal exposure to smoking can be assigned with 81% accuracy using childhood DNAm patterns at these 26 loci. These findings support the potential for blood-derived DNAm measurements to serve as biomarkers for prenatal exposure.