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The Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort study recruited 3624 pregnant women, most partners and 3542 eligible offspring. We hypothesise that early life physical and psychosocial environments, immunological, physiological, nutritional, hormonal and metabolic influences interact with genetics influencing allergic diseases, including asthma. Environmental and biological sampling, innate and adaptive immune responses, gene expression, DNA methylation, gut microbiome and nutrition studies complement repeated environmental and clinical assessments to age 5. This rich data set, linking prenatal and postnatal environments, diverse biological samples and rigorous phenotyping, will inform early developmental pathways to allergy, asthma and other chronic inflammatory diseases. [ABSTRACT FROM AUTHOR]

There is concern that during a low-risk pregnancy, women are consuming more than recommended (400 µg/day) supplemental folic acid and may not meet recommendations for other nutrients. The objective of this study was to determine folic acid supplement use and dietary folate intakes in the second trimester (week 18) of pregnancy in women (n = 2996) in the Canadian CHILD cohort study. Vitamin B12 and choline intakes were also assessed because they are metabolically related to folate. The majority of participants (71.6%) were consuming a daily prenatal supplement. Twenty-eight percent of women (n = 847) reported consuming a folic acid supplement and of these women, 45.3% had daily supplemental folic acid intakes above the upper intake level (UL; 1000 µg/day). Daily dietary folate intakes were (mean (SD)) 575 (235) DFE µg/day. In contrast, only 24.8% of women met the dietary choline adequate intake (AI) recommendation (AI ≥ 450 mg/day) with a mean (SD) intake of 375 (151) mg/day. Further understanding of the impact of supplemental folic acid intake above the UL and low choline intake during pregnancy requires further investigation. [ABSTRACT FROM AUTHOR]

Background: A lack of safety data on postpartum medication use presents a potential barrier to breastfeeding and may result in infant exposure to medications in breastmilk. The type and extent of medication use by lactating women requires investigation. Methods: Data were collected from the CHILD Cohort Study which enrolled pregnant women across Canada between 2008 and 2012. Participants completed questionnaires regarding medications and non-prescription medications used and breastfeeding status at 3, 6 and 12 months postpartum. Medications, along with self-reported reasons for medication use, were categorized by ontologies [hierarchical controlled vocabulary] as part of a large-scale curation effort to enable more robust investigations of reasons for medication use. Results: A total of 3542 mother-infant dyads were recruited to the CHILD study. Breastfeeding rates were 87.4%, 75.3%, 45.5% at 3, 6 and 12 months respectively. About 40% of women who were breastfeeding at 3 months used at least one prescription medication during the first three months postpartum; this proportion decreased over time to 29.5% % at 6 months and 32.8% at 12 months. The most commonly used prescription medication by breastfeeding women was domperidone at 3 months (9.0%, n = 229/2540) and 6 months (5.6%, n = 109/1948), and norethisterone at 12 months (4.1%, n = 48/1180). The vast majority of domperidone use by breastfeeding women (97.3%) was for lactation purposes which is off-label (signifying unapproved use of an approved medication). Non-prescription medications were more often used among breastfeeding than non-breastfeeding women (67.6% versus 48.9% at 3 months, p < 0.0001), The most commonly used non-prescription medications were multivitamins and Vitamin D at 3, 6 and 12 months postpartum. Conclusions: In Canada, medication use is common postpartum; 40% of breastfeeding women use prescription medications in the first 3 months postpartum. A diverse range of medications were used, with many women taking more than one prescription and non-prescription medicines. The most commonly used prescription medication by breastfeeding women were domperidone for off-label lactation support, signalling a need for more data on the efficacy of domperidone for this indication. This data should inform research priorities and communication strategies developed to optimize care during lactation. [ABSTRACT FROM AUTHOR]

BACKGROUND: Evidence suggests that prenatal air pollution exposure alters DNA methylation (DNAm), which could go on to affect long-term health. It remains unclear whether DNAm alterations present at birth persist through early life. Identifying persistent DNAm changes would provide greater insight into the molecular mechanisms contributing to the association of prenatal air pollution exposure with atopic diseases. OBJECTIVES: This study investigated DNAm differences associated with prenatal nitrogen dioxide (NO2) exposure (a surrogate measure of trafficrelated air pollution) at birth and 1 y of age and examined their role in atopic disease. We focused on regions showing persistent DNAm differences from birth to 1 y of age and regions uniquely associated with postnatal NO2 exposure. METHODS: Microarrays measured DNAm at birth and at 1 y of age for an atopy-enriched subset of Canadian Health Infant Longitudinal Development (CHILD) study participants. Individual and regional DNAm differences associated with prenatal NO2 (푛= 128) were identified, and their persistence at age 1 y were investigated using linear mixed effects models (푛= 124). Postnatal-specific DNAm differences (푛= 125) were isolated, and their association with NO2 in the first year of life was examined. Causal mediation investigated whether DNAm differences mediated associations between NO2 and age 1 y atopy or wheeze. Analyses were repeated using biological sex-stratified data. RESULTS: At birth (푛= 128), 18 regions of DNAm were associated with NO2, with several annotated to HOX genes. Some of these regions were specifically identified in males (푛= 73), but not females (푛= 55). The effect of prenatal NO2 across CpGs within altered regions persisted at 1 y of age. No significant mediation effects were identified. Sex-stratified analyses identified postnatal-specific DNAm alterations. DISCUSSION: Regional cord blood DNAm differences associated with prenatal NO2 persisted through at least the first year of life in CHILD participants. Some differences may represent sex-specific alterations, but replication in larger cohorts is needed. The early postnatal period remained a sensitive window to DNAm perturbations. [ABSTRACT FROM AUTHOR]

Background: Comprehensive longitudinal studies are important for understanding the complex risk factors, pathways, exposures and interactions that lead to the development and persistence of asthma. We aimed to examine associations between use of household cleaning products in early life and childhood respiratory and allergic disease using data from the Canadian Healthy Infant Longitudinal Development (CHILD) Cohort Study.Methods: We summed responses from parental questionnaires that indicated the frequency of use of 26 household cleaning products in the homes of 2022 children from this birth cohort when they were 3-4 months of age to create a cumulative Frequency of Use Score (FUS). We used multivariable logistic regression models to assess whether frequent compared with less frequent use was associated with recurrent wheeze, atopy or asthma diagnosis, as defined by the questionnaire and clinical assessments at age 3 years. Data were collected between 2008 and 2015.Results: Children in homes with a higher frequency of use of cleaning products in infancy, as determined by an interquartile range increase, had higher odds of recurrent wheeze (adjusted odds ratio [OR] 1.35, 95% confidence interval [CI] 1.11-1.64), recurrent wheeze with atopy (adjusted OR 1.49, 95% CI 1.02-2.16) and asthma diagnosis (adjusted OR 1.37, 95% CI 1.09-1.70), but no increase in the odds of atopy at age 3 years (adjusted OR 1.14, 95% CI 0.96-1.35). Compared with the lowest tertile of FUS exposure, infants in the highest tertile had higher odds of acquiring asthma. Stratification of the results showed that females had higher ORs than males for all outcomes, although the p values for this sex difference did not reach statistical significance.Interpretation: Frequent use of household cleaning products in early life was associated with an increased risk for childhood wheeze and asthma but not atopy at age 3 years. Our findings add to the understanding of how early life exposures to cleaning products may be associated with the development of allergic airway disease and help to identify household behaviours as a potential area for intervention. [ABSTRACT FROM AUTHOR]

Background: Breastfeeding has many established health benefits for women and children. We examined the association between maternal education, newborn feeding in hospital, and long‐term breastfeeding duration. Methods: We studied 3195 Canadian mother‐infant dyads in the CHILD pregnancy cohort. Newborn feeding was documented from hospital records. Caregivers reported sociodemographic factors and infant feeding at 3, 6, 12, 18, and 24 months. Results: Overall, 97% of newborns initiated breastfeeding and 74% were exclusively breastfed in hospital. Exclusively breastfed newborns were ultimately breastfed longer compared with those who received formula supplementation during their hospital stay (median 11.0 vs 7.0 months, P < .001). After controlling for maternal age, ethnicity, birth mode, and gestational age, exclusively breastfed newborns had a 21% reduced risk of breastfeeding cessation (HR = 0.79, 0.71‐0.87). This effect was strongest among women without a postsecondary education (HR = 0.65, 0.53‐0.79). Discussion: Exclusive breastfeeding in hospital is associated with longer breastfeeding duration, particularly among women of lower socioeconomic status. Initiatives that support exclusive breastfeeding of newborns in hospital could improve long‐term breastfeeding rates and help reduce health inequities arising in early life. [ABSTRACT FROM AUTHOR]

Background: Persisting atopic dermatitis (AD) is known to be associated with more serious allergic diseases at later ages; however, making an accurate diagnosis during infancy is challenging. We assessed the diagnostic performance of questionnaire-based AD measures with criteria-based in-person clinical assessments at age 1 year and evaluated the ability of these diagnostic methods to predict asthma, allergic rhinitis and food allergies at age 5 years.Methods: Data relate to 3014 children participating in the Canadian Healthy Infant Longitudinal Development (CHILD) Study who were directly observed in a clinical assessment by an experienced healthcare professional using the UK Working Party criteria. The majority (2221; 73.7%) of these children also provided multiple other methods of AD ascertainment: a parent reporting a characteristic rash on a questionnaire, a parent reporting the diagnosis provided by an external physician and a combination of these two reports.Results: Relative to the direct clinical assessment, the area under the Receiver Operating Characteristic curve for a parental report of a characteristic rash, reported physician diagnosis and a combination of both were, respectively, 0.60, 0.69 and 0.70. The strongest predictor of asthma at 5 years was AD determined by criteria-based in-person clinical assessment followed by the combination of parental and physician report.Conclusions: These findings suggest that questionnaire data cannot accurately substitute for assessment by experienced healthcare professionals using validated criteria for diagnosis of atopic dermatitis. Combining the parental report with diagnosis by a family physician might sometimes be appropriate (eg to avoid costs of a clinical assessment). [ABSTRACT FROM AUTHOR]

Background: The role of traffic-related air pollution (TRAP) exposure in the development of allergic sensitization in children is unclear, and few birth cohort studies have incorporated spatiotemporal exposure assessment. Objectives: We aimed to examine the association between TRAP and atopy in 1-year-old children from an ongoing national birth cohort study in four Canadian cities. Methods: We identified 2,477 children of approximately 1 year of age with assessment of atopy for inhalant (Alternaria, Der p, Der f, cat, dog, cockroach) and food-related (milk, eggs, peanuts, soy) allergens. Exposure to nitrogen dioxide (NO2) was estimated from city-specific land use regression models accounting for residential mobility and temporal variability in ambient concentrations. We used mixed models to examine associations between atopy and exposure during pregnancy and the first year of life, including adjustment for covariates (maternal atopy, socioeconomic status, pets, mold, nutrition). We also conducted analyses stratified by time-location patterns, daycare attendance, and modeled home ventilation. Results: Following spatiotemporal adjustment, TRAP exposure after birth increased the risk for development of atopy to any allergens [adjusted odds ratio (aOR) per 10 μg/m3 NO2 = 1.16; 95% CI: 1.00, 1.41], but not during pregnancy (aOR = 1.02; 95% CI: 0.86, 1.22). This association was stronger among children not attending daycare (aOR = 1.61; 95% CI: 1.28, 2.01) compared with daycare attendees (aOR = 1.05; 95% CI: 0.81, 1.28). Trends to increased risk were also found for food (aOR = 1.17; 95% CI: 0.95, 1.47) and inhalant allergens (aOR = 1.28; 95% CI: 0.93, 1.76). Conclusion: Using refined exposure estimates that incorporated temporal variability and residential mobility, we found that traffic-related air pollution during the first year of life was associated with atopy. [ABSTRACT FROM AUTHOR]