Nationwide Birth Cohort Study Research Articles

Maternal Exposure to Per- and Polyfluoroalkyl Substances and Offspring Chromosomal Abnormalities: The Japan Environment and Children's Study.

Although recent in vitro experimental results have raised the question of whether maternal exposure to per- and polyfluoroalkyl substances (PFAS) may be a potential environmental risk factor for chromosomal abnormalities, epidemiological studies investigating these associations are lacking. This study examined whether prenatal PFAS exposure is associated with a higher prevalence of chromosomal abnormalities among offspring. We used data from the Japan Environment and Children's Study, a nationwide birth cohort study, and employed logistic regression models to examine the associations between maternal plasma PFAS concentrations in the first trimester and the diagnosis of chromosomal abnormalities in all births (artificial abortions, miscarriages, stillbirths, and live births) up to 2 years of age. In addition, we examined associations with mixtures of PFAS using multipollutant models. The final sample consisted of 24,724 births with singleton pregnancies, of which 44 confirmed cases of chromosomal abnormalities were identified (prevalence: 17.8/10,000 births). When examined individually, exposure to perfluorononanoic acid (PFNA) and perfluorooctane sulfonic acid (PFOS) showed positive associations with any chromosomal abnormalities with age-adjusted odds ratios of 1.81 (95% CI: 1.26, 2.61) and 2.08 (95% CI: 1.41, 3.07) per doubling in concentration, respectively. These associations remained significant after Bonferroni correction, although they did not reach the adjusted significance threshold in certain sensitivity analyses. Furthermore, the doubling in all PFAS included as a mixture was associated with chromosomal abnormalities, indicating an age-adjusted odds ratio of 2.25 (95% CI: 1.34, 3.80), with PFOS as the predominant contributor, followed by PFNA, perfluoroundecanoic acid (PFUnA), and perfluorooctanoic acid (PFOA). The study findings suggested a potential association between maternal exposure to PFAS, particularly PFOS, and chromosomal abnormalities in offspring. However, the results should be interpreted cautiously, because selection bias arising from the recruitment of women in early pregnancy may explain the associations. https://doi.org/10.1289/EHP13617.

Association of phenol exposure during pregnancy and asthma development in children: The Japan Environment and Children's study

BackgroundAlkylphenols can originate from numerous products containing alkylphenol ethoxylates, including cleaning products, household items, and cosmetics. Some phenols, such as nonylphenol, are known to be endocrine disruptors, and exposure to them is thought to have contributed to the recent increase in allergic diseases such as asthma. However, the impacts of prenatal phenol exposure on asthma development in children are still unclear. MethodsWe analyzed the association between maternal urinary phenol concentrations during early pregnancy and the development of asthma in children at the age of 4, using data from the Japan Environment and Children's Study (JECS), a large-scale nationwide birth cohort study. ResultsWe recruited 3,513 pairs of mothers and children participating in the Sub-Cohort Study of JECS. We measured 24 phenols, including nitrophenol, parabens, bisphenol, octylphenol, and nonylphenol, in urine samples taken during the first trimester of pregnancy. The urinary levels of these phenols differed markedly, and some showed a broad spectrum of distribution. Methylparaben was detected at high levels in almost every participant (267.7 ng/ml, standard deviation 433.78). Logistic regression analysis revealed that the odds ratio of asthma onset for high exposure to butylparaben was 1.54 (95% confidence interval: 1.11–2.15). Additionally, logistic regression analysis by gender revealed an asthma development odds ratio of 2.09 (95% confidence interval: 1.20–3.65) for males and 0.65 (95% confidence interval: 0.25–1.70) for females born to mothers in whom 4-nonylphenol was detected, suggesting a gender difference. ConclusionOur current analysis using large cohort data suggests that high exposure to butylparaben and low exposure to 4-nonylphenol during pregnancy are risk factors for asthma development in children. These findings establish a valuable foundation for formulating recommendations about prenatal phenol exposure.

Prenatal and infant exposure to antibiotics and subsequent risk of neuropsychiatric disorders in children: A nationwide birth cohort study in South Korea

We aimed to assess the association between antibiotic exposure in fetal and postnatal life (within six months after birth) and the risk of neuropsychiatric disorders in childhood. A nationwide, population-based birth cohort study(infants, n = 3,163,206; paired mothers, n = 2,322,735) was conducted in South Korea, with a mean follow-up duration of 6.8 years, using estimates of hazard ratio [HR] and 95 % confidence intervals (CIs).Following propensity score matching including the baseline variables, antibiotic exposure in both fetal (HR,1.07 [95 % CI, 1.05–1.08]) and postnatal life (1.05 [1.03–1.07]) was associated with an increased risk of overall childhood neuropsychiatric disorders. A synergistic effect was observed with prenatal and postnatal exposures (1.12 [1.09–1.15]). The risk increases with the increasing number and duration of prescriptions. Significant associations were found for both common (1.06 [1.05–1.08]) and severe outcomes (1.17 [1.09–1.26]), especially for intellectual disability (1.12 [1.07–1.17]), ADHD (1.10 [1.07–1.13]), anxiety (1.06 [1.02–1.11]), mood (1.06 [1.00–1.12]), and autism (1.03 [1.01–1.07]). When comparing siblings with different exposure statuses to consider familial factors, prenatal and postnatal exposure risk increased to 10 % (95 % CI, 6–12) and 12 % (7–17), respectively. Similar results were observed in the unmatched and health screening cohort, which considers maternal obesity, smoking, and breastfeeding. Based on these findings, clinicians may consider potential long-term risks when assessing the risk-benefit of early-life antibiotic prescription.

Associations between paternal autism traits and parenting from the Japan environment and children’s study

There are few studies on the parenting of fathers with autism traits. To investigate this issue, we examined the type of parenting performed by fathers with autism traits using data from a nationwide birth cohort study, the Japan Environment and Children’s Study. Paternal parenting was evaluated by mothers or caregivers when the child was 2 years old. Father’s autism traits were measured using the Japanese version of the self-administered Autism Spectrum Quotient. Logistic regression analysis was performed to statistically analyze the data. Fathers with autism traits were significantly less likely to prepare meals for their child and helping them eat (adjusted OR (aOR): 1.11, 95% confidence interval (CI): 1.01–1.23), to helping the child change clothes (aOR: 1.17, 95% CI: 1.04–1.31). However, there were no associations between some parenting behaviors and autism traits (not changing diapers, not bathing with the child, and not playing with the child). Father’s communication skill difficulties by autism traits associated with a lower tendency to perform all types of parenting. Interestingly, there were association between difficulties with social skills or attention-switching and more performing change diapers. These results indicate it is important to respect the child-rearing that fathers with autistic tendencies are able to do, while supporting them in child-rearing that they are significantly less able to do than fathers without autistic tendencies.

Prenatal opioid exposure and subsequent risk of neuropsychiatric disorders in children: nationwide birth cohort study in South Korea

SummaryObjectiveTo investigate the potential association between prenatal opioid exposure and the risk of neuropsychiatric disorders in children.DesignNationwide birth cohort study.SettingFrom 1 January 2009 to 31 December 2020, birth cohort data...

Assisted reproductive techniques and subsequent risk of asthma and allergic rhinitis in offspring: a nationwide birth cohort study in South Korea.

The relationship between assisted reproductive techniques (ART) and the risk of asthma and allergic rhinitis (AR) is controversial. Thus, we aimed to investigate the relationship between ART and the risk of asthma and AR in a nationwide, large-scale birth cohort. This study utilized the National Health Insurance Service data in South Korea to conduct a nationwide, large-scale, population-based birth cohort. We included all infants born between 2017 and 2018. AR, asthma, food allergies, and atopic dermatitis were defined using the International Classification of Diseases tenth edition codes. Asthma was classified as allergic or non-allergic based on accompanying allergic diseases (AR, food allergy, or atopic dermatitis). Using 1:10 propensity score matching, we compared infants conceived through ART with those conceived naturally (non-ART). After matching, logistic regression was used to compare the hazard ratio for asthma and AR between the two groups. We included 543,178 infants [male infants, 280,194 (51.38%)]. After matching, 8,925 and 74,229 infants were selected for the ART and non-ART groups, respectively. The ART group showed a decreased risk of asthma in the offspring [adjusted hazard ratio (aHR), 0.45; 95% confidence interval (CI), 0.41-0.48]. Similarly, for AR, being conceived by ART was associated with a decreased risk of AR (aHR, 0.25; 95% CI, 0.12-0.37). ART offspring showed a decreased risk of asthma and AR in offspring compared to that observed in non-ART offspring. Our study offers important insights for clinicians, researchers, and parents regarding the health outcomes of ART-conceived infants and enhances our understanding of ART's impact on respiratory health.

Prenatal and postnatal exposure to antibiotics and risk of food allergy in the offspring: A nationwide birth cohort study in South Korea.

There are only preliminary studies examining the associations of postnatal antibiotic exposure with food allergy in childhood, and the effect of antibiotic exposure in utero has not been resolved. Thus, we aimed to investigate the effect of prenatal and postnatal antibiotic exposure on the risk of food allergy in childhood. Using the nationwide birth cohort in South Korea, all 3,163,206 infants (pairing mother; n = 2,322,735) born in South Korea between 2010 and 2017 were included in the analysis. The primary outcome was the diagnosis of food allergy, and the observation period was between January 1, 2009, and December 31, 2020. We implemented four different designs for the study, which consisted of a full unmatched cohort, 1:1 propensity-matched cohort, sibling comparison cohort, and health screening cohort along with multiple subgroup analyses. During the follow-up period (median 6.92 years [IQR, 4.72-9.00]) of the 3,161,858 infants (52.6% male) in the birth cohort, 29,973 (1.9%) were diagnosed with food allergies. After a 1:1 propensity score matching, the use of antibiotics increased the risk of overall food allergy (prenatal [HR, 1.05; 95% CI, 1.04-1.09] and postnatal [HR, 1.05; 95% CI, 1.01-1.10] periods). The association was more significantly accentuated when antibiotic exposure was used in the short term, and the children were born preterm or with low birthweight; however, a trimester-specific effect was not observed. We observed more pronounced risks of food allergy in the health screening cohort (prenatal, 17%; postnatal, 15%), thus addressing the adverse effects of critical factors including maternal BMI, smoking status, and type of infant feeding. Similar trends were observed across all four differnt cohorts. This study reported a moderate association between early-life antibiotic use and subsequent food allergy during childhood throughout four different designs of analyses. This study suggests that clinicians need to consider the risks and benefits of antibiotics when administering antibiotics to individuals in the prenatal and postnatal periods.

Mortality risk among Autistic children and young people: A nationwide birth cohort study.

Existing literature indicates that Autistic people have shorter life expectancy, but little is known about the mortality risk among Autistic children and young people (0-24 years). We used a 15-year nationwide birth cohort study to estimate the mortality risk among Autistic children and young people in Aotearoa/New Zealand. The study included 895,707 children and 11,919 (1.4%) were Autistic. We found that autism was associated with a significantly higher mortality risk compared to the non-Autistic population. In addition, we found that this risk was significantly higher among females compared to males and for those with a co-occurring intellectual disability. Increased efforts are required to better meet the health needs of this population.

Hypertensive disorders of pregnancy increase the incidence of febrile seizures in offspring.

Intrauterine exposure to hypertensive disorders of pregnancy (HDP) may increase the risk of neuropsychiatric disorders. This investigation examined for associations between maternal HDP and febrile seizures (FS) in offspring by the age of three years. The present cohort study analyzed data from the Japan Environment and Children's Study, a large national birth cohort. We included mother-child pairs recruited between January 2011 and March 2014. Information regarding maternal HDP, the presence of FS in offspring up to 3 years of age, and potential confounding factors were assessed using written questionnaires administered to mothers. A total of 77,699 mother-child dyads were analyzed. The prevalence of FS was 8.4% in children without HDP exposure, 10.6% in those exposed to mild HDP, and 10.4% in those with severe HDP exposure. Among children with full-term birth, logistic regression analysis indicated that exposure to mild or severe HDP was significantly associated with a higher incidence of FS (adjusted odds ratio [95% confidence interval]: 1.27 [1.05-1.53] and 1.27 [0.90-1.78], respectively, P for trend = 0.008), compared with children without HDP exposure. In children with full-term birth, intrauterine exposure to HDP was significantly associated with FS by the age of three years. This study revealed a significant association between intrauterine exposure to hypertensive disorders of pregnancy (HDP) and the subsequent development of febrile seizures (FS) in offspring by three years. This increased incidence of FS by HDP was independent of preterm birth status. This is the first large nationwide birth cohort study showing the impact of intrauterine exposure to HDP on FS in early childhood.

Urinary 8-hydroxy-2′-deoxyguanosine levels and preterm births: a prospective cohort study from the Japan Environment and Children’s Study

ObjectivesTo evaluate the association between urinary 8-hydroxy-2′-deoxyguanosine (U8-OHdG) level—a marker of oxidative stress—and the incidence of preterm births (PTBs).DesignProspective cohort study.SettingThe Japan Environment and Children’s Study (JECS).ParticipantsData from 92 715...

Association of allergies in children younger than 3 years with levels of maternal intake of n-3 polyunsaturated fatty acids or fish during pregnancy: A nationwide birth cohort study, the Japan Environment and Children's Study

BackgroundN-3 polyunsaturated fatty acids (PUFAs) have anti-inflammatory properties and are expected to prevent the onset of allergies. However, epidemiological studies investigating the relationship between child allergies and maternal intake of n-3 PUFAs or fish have yielded inconsistent results. MethodsFollowing exclusions from a dataset comprising 103,057 records from the Japan Environment and Children's Study, 72,105 participants were divided into five groups according to mothers' intake of n-3 PUFAs or fish during pregnancy to assess the risk of their children being diagnosed with allergy by 3 years old. Adjusted odds ratios (aORs) with 95% confidence intervals (CIs) for child allergies were calculated using multivariable logistic regression analyses with reference to the lowest intake group. ResultsLevels of maternal intake of n-3 PUFAs or fish showed inverted associations (i.e., reduced risk) with the incidence of physician-diagnosed allergic rhinoconjunctivitis or parent-reported symptoms of current rhinitis with eye symptoms at different time points and the cumulative incidence from birth to 3 years of age. Inverted associations were also found for current wheeze at 1-<2 years of age and current eczema at 1-<2 and 0-<3 years of age. However, for food allergies, no significant associations were observed in the incidence in each group compared with the lowest intake group at any age. ConclusionsThe findings suggest that n-3 PUFA intake during pregnancy may reduce the risk of developing allergic diseases and symptoms in children. In addition, consumption of n-3 PUFAs or fish is very unlikely to increase the risk of allergy given that the results are from a country with high fish consumption. Trial registration: UMIN000030786 https://rctportal.niph.go.jp/detail/um?trial_id=UMIN000030786.

Maternal greenness exposure and preterm birth in Brazil: A nationwide birth cohort study

In the dynamic landscape of maternal and child health, understanding the intricate interplay between environmental factors and pregnancy outcomes is of paramount importance. This study investigates the relationship between maternal greenness exposure and preterm births in Brazil using data spanning from 2010 to 2019. Satellite-derived indices, including the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), were employed to assess greenness exposure during whole pregnancy in maternal residential area. Employing Cox proportional hazard models, we calculated the hazard ratios (HRs) with 95% confidence intervals (CIs) for changes in NDVI, while adjusting for individual and area-level covariates. In total, 24,010,250 live births were included. Prevalence of preterm birth was 11.5%, with a modest but statistically significant decreasing trend (p = 0.013) observed across the nation over the study period. The findings reveal a significant association between greenness exposure and a reduced risk of preterm birth. Specifically, for every 0.1 increase in NDVI, there was a 2.0% decrease in the risk of preterm birth (95%CI: 1.9%–2.2%). Stratified analyses based on maternal education and ethnicity indicated potential effect modifications, with stronger protective effects observed among younger mothers and those with less years of education. Sensitivity analyses using EVI yielded consistent results. In conclusion, this study suggests that higher maternal greenness exposure is linked to a decreased risk of preterm birth in Brazil. These findings imply that enhancing residential greenspaces could be a valuable public health strategy to promote maternal and child health in Brazil.

Maternal SARS-CoV-2 infection during pregnancy and subsequent risk of atopic dermatitis in offspring: a nationwide birth cohort study in South Korea.

Although previous studies suggest an association between SARS-CoV-2 infection and atopic dermatitis (AD) in adults, insufficient attention has been given to the impact of SARS-CoV-2 infection on pregnant woman and their offspring. Evidence on prenatal SARS-CoV-2 infection and subsequent risk of AD is lacking; therefore, we aimed to investigate the risk of AD in infants born to women who were infected with SARS-CoV-2 during pregnancy.

Associations between type 1 diabetes and educational outcomes: an Aotearoa/New Zealand nationwide birth cohort study using the Integrated Data Infrastructure

Aims/hypothesisType 1 diabetes is one of the most common chronic diseases of childhood. It is hypothesised that the metabolic and psychosocial consequences of type 1 diabetes may affect educational outcomes; however, existing literature presents conflicting results. This study aimed to assess whether educational outcomes differ for young people with and without type 1 diabetes in Aotearoa/New Zealand (NZ).MethodsThis was a nationwide 9 year birth cohort study of all people born in NZ from 1993 to 2001 using linked administrative data held within the Integrated Data Infrastructure, a national research database containing linked health and non-health data. Educational outcomes of high school attainment, high school attendance and university enrolment were measured from age 13 years until 20 years. Generalised linear regression models with log link and Gaussian distributions were used to compare educational outcomes between those with and those without type 1 diabetes, adjusting for sociodemographic and maternal characteristics.ResultsOf the 442,320 children in the birth cohort, type 1 diabetes was identified in 2058 (0.47%) (mean [SD] age of type 1 diabetes diagnosis 7.7 [3.4] years). Educational outcomes were significantly lower for children with type 1 diabetes than for those without type 1 diabetes, including for any high school qualification (RR 0.97 [95% CI 0.95, 0.99]), university entrance-level high school attainment (RR 0.88 [95% CI 0.84, 0.92]), regular high school attendance (RR 0.91 [95% CI 0.85, 0.97]) and university enrolment (RR 0.93 [95% CI 0.88, 0.98]), even after adjusting for sociodemographic and maternal factors. In addition, educational outcomes were substantially lower for those with post type 1 diabetes diagnosis hospitalisations for diabetic ketoacidosis and hypoglycaemia.Conclusions/interpretationIn this whole NZ birth cohort study, type 1 diabetes was associated with lower educational outcomes spanning secondary school and into university enrolment. Ongoing efforts to support students with type 1 diabetes are needed, particularly for those with a greater risk profile.Graphical

Maternal Dietary Vitamin D Intake during Pregnancy Is Associated with Allergic Disease Symptoms in Children at 3 Years Old: The Japan Environment and Children’s Study

Introduction: Vitamin D plays an important role in the immune system, and postnatal vitamin D insufficiency is one of the risk factors for the development of allergic disease. However, the effects of women’s vitamin D intake during pregnancy on the prevalence of allergic disease in their children remain controversial. Methods: From the Japan Environment and Children’s Study, an ongoing nationwide birth cohort study, we obtained information on maternal dietary vitamin D intake determined using a food frequency questionnaire and parent-reported allergic disease symptoms based on the ISAAC questionnaire in children at 3 years of age. Results: From the full dataset of 103,060 pregnancies, we analyzed complete data for 73,309 mother-child pairs. The prevalence of current wheeze, current rhinitis, current rhino-conjunctivitis, current eczema, ever asthma, ever pollinosis, and ever atopic dermatitis in the children was 17.2%, 29.7%, 3.8%, 15.2%, 9.6%, 3.7%, and 11.0%, respectively. The ORs for current rhinitis were significantly lower in the 3rd, 4th, and 5th quintiles than in the 1st quintile after adjustment for various covariates and showed a linear association. The ORs for ever pollinosis were significantly lower in the 2nd, 3rd, and 4th quintiles than in the 1st quintile, showing a U-shaped curve. There was no clear association between mothers’ dietary vitamin D intake and symptoms of asthma or atopic dermatitis in their 3-year-old children. Conclusion: Maternal dietary vitamin D intake during pregnancy is associated with the ORs for nasal allergies in children at the age of 3 years. Further studies are warranted to evaluate the appropriate intake dose of vitamin D for pregnant women to prevent the development of nasal allergies in their children.

Association of Fine Particulate Matter and Its Components with Macrosomia: A Nationwide Birth Cohort Study of 336 Chinese Cities.

To examine the associations between macrosomia risk and exposure to fine particulate matter (PM2.5) and its chemical components during pregnancy, we collected birth records between 2010 and 2015 in mainland China from the National Free Preconception Health Examination Project and used satellite-based models to estimate concentrations of PM2.5 mass and five main components, namely, black carbon (BC), organic carbon (OC), nitrate (NO3-), sulfate (SO42-), and ammonium (NH4+). Associations between macrosomia risk and prenatal exposure to PM2.5 were examined by logistic regression analysis, and the sensitive subgroups were explored by stratified analyses. Of the 3,248,263 singleton newborns from 336 cities, 165,119 (5.1%) had macrosomia. Each interquartile range increase in concentration of PM2.5 during the entire pregnancy was associated with increased risk of macrosomia (odds ratio (OR) = 1.18; 95% confidence interval (CI), 1.17-1.20). Among specific components, the largest effect estimates were found on NO3- (OR = 1.36; 95% CI, 1.35-1.38) followed by OC (OR = 1.23; 95% CI, 1.22-1.24), NH4+ (OR = 1.22; 95% CI, 1.21-1.23), and BC (OR = 1.21; 95% CI, 1.20-1.22). We also that found boys, women with a normal or lower prepregnancy body mass index, and women with irregular or no folic acid supplementation experienced higher risk of macrosomia associated with PM2.5 exposure.

Impact of Habitual Yogurt Intake in Mother-Child Dyads on Incidence of Childhood Otitis Media: The Japan Environment and Children's Study (JECS).

Otitis media, one of the most common childhood diseases, is characterized by inflammation or infection of the middle ear. Due to their ease of access, daily probiotics are recommended for the prevention of early childhood otitis media. This study aimed to assess the impact of probiotics on the incidence of otitis media using a dataset (n = 95,380) from the Japan Environment and Children's Study, a nationwide birth cohort study. After multiple imputations, the association between the incidence of otitis media in early childhood and the daily frequency of yogurt intake in children and mothers was examined using a generalized linear model after adjusting for several confounders. Repeated incidence of otitis media during the 2years after birth was found in 14,874 participants (15.6%). Based on participants with the lowest frequency of yogurt intake ("almost never") as the reference group, risk ratios for otitis media incidence decreased with higher frequencies of yogurt intake in children at one year of age, but also independently in mothers during pregnancy. The lowest risk ratio (95% confidence interval) for otitis media incidence at six months of age was observed with the most frequent yogurt intake (once/day or more) (0.54 [0.46-0.63]). Additionally, although a similar association was observed in the subgroup of those with cleft lip and/or palate (CL/P), a high-risk group for severe recurrent otitis media, no statistical significance was observed. Thus, increased regular yogurt intake in both children and mothers was associated with a decrease of otitis media during early childhood.

Weight-loss behaviors before pregnancy associate with increased risk of postpartum depression from the Japan Environment and Children’s Study

No studies showed the association between weight-loss behaviors before pregnancy and postpartum depression (PPD). We analyzed data from the nation-wide birth cohort study, the Japan Environment and Children’s Study. Self-administrated questionnaires answered by 62,446 women was analyzed using logistic regression analysis. PPD was assessed using the Edinburgh Postnatal Depression Scale at 1 month after delivery. Women using at least one weight-loss method had higher risk of PPD than women using no weight-loss methods [women without antenatal psychological distress according to Kessler 6-Item Psychological Distress score: adjusted odds ratio (aOR) 1.318, 95% confidence interval (CI) 1.246–1.394; women with antenatal psychological distress: aOR 1.250, 95% CI 0.999–1.565]. Using extremely unhealthy weight-loss methods was associated with PPD compared with no use of each weight-loss method (vomiting after eating: aOR 1.743, 95% CI 1.465–2.065; smoking: aOR 1.432, 95% CI 1.287–1.591; taking diet pills: aOR 1.308, 95% CI 1.122–1.520). The association between weight-loss behaviors and PPD varied according to pre-pregnancy BMI. In normal-weight women, the weight-loss method score, which indicates the degree of weight-loss method use, was associated with PPD. These results indicate using weight-loss methods before pregnancy is associated with an increased risk of PPD in Japanese women.

Early-Life Exposure to Ambient Air Pollution from Multiple Sources and Asthma Incidence in Children: A Nationwide Birth Cohort Study from Denmark.

Ambient air pollution exposure has been associated with childhood asthma, but previous studies have primarily focused on prevalence of asthma and asthma-related outcomes and urban traffic-related exposures. We examined nationwide associations between pre- and postnatal exposure to ambient air pollution components and asthma incidence in children age 0-19 y. Asthma incidence was identified from hospital admission, emergency room, and outpatient contacts among all live-born singletons born in Denmark between 1998 and 2016. We linked registry data with monthly mean concentrations of particulate matter (PM) with aerodynamic diameter () and PM with aerodynamic diameter (), nitrogen dioxide (), nitrogen oxides, elemental carbon, and organic carbon (OC), sulfur dioxide, ozone, sulfate, nitrate, ammonium, secondary organic aerosols, and sea salt. Associations were estimated with Cox proportional hazard models using fixed prenatal exposure means and time-varying postnatal exposures. Of the 1,060,154 children included, 6.1% had asthma during the mean follow-up period of 8.8 y. The risk of asthma increased with increasing prenatal exposure to all pollutants except for and sea salt. We also observed increased risk after restriction to asthma after age 4 y, after additional adjustment for area-specific socioeconomic status, and for postnatal exposure to most pollutants. The hazard ratio (HR) associated with an interquartile range increase of 2.4 and in prenatal exposure was 1.06 [95% confidence interval (CI): 1.04, 1.08] for and 1.04 (95% CI: 1.02, 1.05) for , respectively. This association with was stable after adjustment for , whereas it attenuated for to 1.01 (95% CI: 0.99, 1.03) after adjustment for . For a increase in prenatal OC exposure, for which biomass is an important source, the HR was 1.08 (95% CI: 1.06, 1.10), irrespective of adjustment for . These findings suggest that early-life exposure to ambient air pollution from multiple sources contributes to asthma development. https://doi.org/10.1289/EHP11539.

Relationship between prenatal checkup status and low birth weight: a nationwide birth cohort–the Japan Environment and Children’s Study

PurposeWe investigated the association between prenatal checkup status and low birth weight (LBW). We also sought to identify the background factors of pregnant women that influence their attendance at prenatal checkups and consider measures that might prove useful in reducing the LBW rate. MethodsUsing data from a large nationwide birth cohort study, the Japan Environment and Children’s Study (JECS), the sample comprised 91,916 unique mother–infant pairs with singleton live births. The outcome variable was cases of LBW, and the exposure variable was prenatal checkup status (number of visits missed). Adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were calculated by logistic regression analysis. ResultsAORs (95% CIs) for cases of LBW were 1.57 (1.46–1.69) for 1 missed checkup, 2.40 (1.97–2.94) for 2 missed checkups, and 2.38 (1.46–3.88) for ≥3 missed checkups. A linear trend was also observed (P < .0001). Further analysis revealed that the main risk factors for missed checkups were divorced or widowed marital status, followed by negative attitude toward pregnancy, and single marital status, whereas protective factors were being employed and better mental health in mid-late pregnancy. ConclusionsOur results suggest the importance of implementing various measures to promote regular attendance at prenatal checkups.