Maternal infections in pregnancy and the development of asthma among offspring

Maternal prenatal immunity, neonatal trained immunity, and early airway microbiota shape childhood asthma development

BACKGROUND

The path to childhood asthma is thought to initiate in utero and be further promoted by postnatal exposures. However, the underlying mechanisms remain underexplored. We hypothesized that prenatal maternal immune dysfunction associated with increased childhood asthma risk (revealed by low IFN-γ:IL-13 secretion during the third trimester of pregnancy) alters neonatal immune training through epigenetic mechanisms and promotes early-life airway colonization by asthmagenic microbiota.

METHODS

We examined epigenetic, immunologic, and microbial features potentially related to maternal prenatal immunity (IFN-γ:IL-13 ratio) and childhood asthma in a birth cohort of mother-child dyads sampled pre-, peri-, and postnatally (N = 155). Epigenome-wide DNA methylation and cytokine production were assessed in cord blood mononuclear cells (CBMC) by array profiling and ELISA, respectively. Nasopharyngeal microbiome composition was characterized at age 2-36 months by 16S rRNA sequencing.

RESULTS

Maternal prenatal immune status related to methylome profiles in neonates born to non-asthmatic mothers. A module of differentially methylated CpG sites enriched for microbe-responsive elements was associated with childhood asthma. In vitro responsiveness to microbial products was impaired in CBMCs from neonates born to mothers with the lowest IFN-γ:IL-13 ratio, suggesting defective neonatal innate immunity in those who developed asthma during childhood. These infants exhibited a distinct pattern of upper airway microbiota development characterized by early-life colonization by Haemophilus that transitioned to a Moraxella-dominated microbiota by age 36 months.

CONCLUSIONS

Maternal prenatal immune status shapes asthma development in her child by altering the epigenome and trained innate immunity at birth, and is associated with pathologic upper airway microbial colonization in early life.

Association of juvenile idiopathic arthritis with maternal infection: a case control study

OBJECTIVE

Maternal infection has been posited as a risk factor for childhood autoimmune disease such as type I diabetes. Given that similar studies in JIA are scant, our objective was to evaluate the association between Juvenile Idiopathic Arthritis (JIA) and maternal infection.

METHODS

This case-control study used an existing database that included 1290 JIA cases and 6072 controls matched on birth year. Maternal infection information was obtained from Washington State birth records. JIA diagnosis and categories were confirmed through chart review. Logistic regression was used to calculate adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs).

RESULTS

JIA was not associated with maternal infection (OR = 1.02, 95%CI: 0.8-1.3). There was no association between JIA and maternal infection for persistent oligoarticular, RF negative polyarticular, or enthesitis-related JIA. There was suggestive evidence of an increased association of maternal infection with JIA in females in sex-stratified analysis.

CONCLUSIONS

We did not observe an increased risk of JIA in children exposed to maternal infection. Suggestive evidence of differential sex-specific results warrants further study.

The Role of Early Life Microbiota Composition in the Development of Allergic Diseases

Allergic diseases are becoming a major healthcare issue in many developed nations, where living environment and lifestyle are most predominantly distinct. Such differences include urbanized, industrialized living environments, overused hygiene products, antibiotics, stationary lifestyle, and fast-food-based diets, which tend to reduce microbial diversity and lead to impaired immune protection, which further increase the development of allergic diseases. At the same time, studies have also shown that modulating a microbiocidal community can ameliorate allergic symptoms. Therefore, in this paper, we aimed to review recent findings on the potential role of human microbiota in the gastrointestinal tract, surface of skin, and respiratory tract in the development of allergic diseases. Furthermore, we addressed a potential therapeutic or even preventive strategy for such allergic diseases by modulating human microbial composition.

Association between gestational hair dye use and allergies at 3 years old: the Japan environment and Children's study

BACKGROUND

Hair dye use frequently induces allergic contact dermatitis, and on rare occasions induces immunoglobulin E-mediated immediate urticaria, anaphylaxis, and asthma. The effects of hair dye use during pregnancy on offspring have been studied for carcinogenicity, but not for development of allergies. This study aimed to assess the association between hair dye use during pregnancy and allergic disease in children at 3 years old.

METHODS

Data of 77,303 participants from the Japan Environment and Children's Study, which is a prospective birth cohort recruited from January 2011 to March 2014, were used. We examined the associations between using hair dye during pregnancy and allergic diseases (food allergy, asthma, atopic dermatitis and allergic rhinitis) in children after adjustment for covariates by multivariable logistic regression.

RESULTS

Among mothers who were exposed to hair dye during pregnancy, 50.0% were exposed in hair salons, 21.3% had home use, and 9.5% had occupational exposure. The percentages of doctor-diagnosed allergies at 3 years old were 6.3% for food allergies, 7.7% for asthma, 7.3% for atopic dermatitis, and 4.6% for allergic rhinitis. In univariable analyses, hair dye use at home and occupational exposure was significantly associated with asthma respectively (odds ratio [OR] 1.15, 95% CI 1.07-1.24 for at home; OR 1.18, 95% CI 1.08-1.28 for occupational exposure). Hair dye use at home were significantly associated with doctor-diagnosed allergic rhinitis at 3 years old (OR 1.12, 95% CI 1.02-1.22). After adjustment for covariates, these associations for asthma decreased and were no longer significant (aOR 1.06, 95% CI 0.98-1.14 for at home; aOR 1.09, 95% CI 1.00-1.20 for occupational exposure, p = 0.057), also for allergic rhinitis (aOR 1.07, 95% CI 0.97-1.19). Doctor-diagnosed allergic rhinitis at 3 years old was significantly associated with hair dye use at home in the most frequent use group (aOR for quite often versus never 1.78, 95% CI 1.22-2.60).

CONCLUSION

Both home and occupation use of hair dye during pregnancy showed a trend of increased odds of allergic rhinitis and asthma in offspring at 3 years. However, the only association that reached significance was in frequency of use analyses between the highest frequency of home hair dye users and allergic rhinitis.

Dose, Timing, and Spectrum of Prenatal Antibiotic Exposure and Risk of Childhood Asthma

BACKGROUND

The potential for prenatal antibiotic exposure to influence asthma risk is not clear. We aimed to determine the effect of timing, dose, and spectrum of prenatal antibiotic exposure on the risk of childhood asthma.

METHODS

We conducted a population-based cohort study of 84 214 mother-child dyads to examine the association of prenatal antibiotic exposure and childhood asthma using multivariable logistic regression models.

RESULTS

Sixty-four percent of pregnant women received antibiotics. Prenatal antibiotic exposure was associated dose-dependently with increased odds of childhood asthma (adjusted odds ratio [aOR] for interquartile increase of 2 courses [interquartile range, 0-2], 1.26 [95% confidence interval {CI}, 1.20-1.33]). Among children exposed to at least 1 course in utero, the effect of timing at the first course was moderated by total maternal courses. Among pregnant women receiving a single antibiotic course, timing of exposure had no effect on childhood asthma risk. Among women receiving > 1 course, early exposure of the first course was associated with greater childhood asthma risk. Compared to narrow spectrum-only antibiotic use, broad spectrum-only antibiotic exposure was associated with increased odds of asthma (aOR, 1.14 [95% CI, 1.05-1.24]). There were effect modifications (P < .001) by maternal asthma on total courses, and on timing of the first course, significant only among those without maternal asthma.

CONCLUSIONS

Increased cumulative dose, early pregnancy first course, and broad-spectrum antibiotic exposure were associated with childhood asthma risk. Our study provides important evidence supporting judicious prenatal antibiotic use, particularly timing of use and choice of antibiotics, in preventing subsequent childhood asthma.

C hlamydia trachomatis during pregnancy and childhood asthma-related morbidity: a population-based prospective cohort

INTRODUCTION

Chlamydia trachomatis is the most commonly reported sexually transmitted disease and although infection during pregnancy is associated with neonatal complications, long-term respiratory consequences are unknown. We aimed to determine whether C. trachomatis infection during pregnancy is associated with asthma-related symptoms across childhood METHODS: This study among 2475 children and their mothers was embedded in a population-based prospective cohort study. Maternal urine samples were tested for C. trachomatis infection during pregnancy. Questionnaires provided information on childhood physician-attended lower respiratory tract infections and wheezing, and current asthma at age 10 years. Lung function was measured by spirometry at age 10 years.

RESULTS

The prevalence of C. trachomatis infection during pregnancy was 3.2% (78 out of 2475). C. trachomatis infection during pregnancy was not associated with lower respiratory tract infections until age 6 years, but was associated with a higher odds of wheezing in children until age 10 years (OR 1.50 (95% CI 1.10-2.03)). C. trachomatis infection during pregnancy was associated with an increased odds of asthma (OR 2.29 (95% CI 1.02-5.13)), and with a lower forced expiratory volume in 1 s/forced vital capacity and forced expiratory flow at 75% of forced vital capacity (z-score difference -0.28 (95% CI -0.52- -0.04) and -0.24 (95% CI -0.46- -0.01), respectively) in children at age 10 years. The observed associations were only partly explained by mode of delivery, gestational age at birth or birthweight.

CONCLUSIONS

C. trachomatis infection during pregnancy is associated with increased odds of wheezing, asthma and impaired lung function. The causality of the observed associations and potential underlying mechanisms need to be explored.

Association between antibiotic treatment during pregnancy and infancy and the development of allergic diseases

BACKGROUND

Allergies are a serious public health issue, and prevalences are rising worldwide. The role of antibiotics in the development of allergies has repeatedly been discussed, as results remain inconsistent. The aim of this study was to investigate the association between pre- and post-natal antibiotic exposure and subsequent development of allergies (atopic dermatitis, food allergy, asthma, atopic sensitization and allergic rhinitis).

METHODS

A total of 1080 children who participated in a European birth cohort study (PASTURE) were included in this analysis. Data on antibiotic exposure during pregnancy and/or first year of life and allergic diseases were collected by questionnaires from pregnancy up to 6 years of age and analysed by performing logistic regressions. To take into account reverse causation, we included models, where children with diagnosis or symptoms of the respective disease in the first year of life were excluded.

RESULTS

Antibiotic exposure in utero was significantly and positively associated with atopic dermatitis and food allergy. The strongest effect was on diseases with onset within the first year of life (for atopic dermatitis: aOR 1.66, 95% CI 1.11-2.48 and for food allergy: aOR 3.01, 95% CI 1.22-7.47). Antibiotics in the first year of life were positively associated with atopic dermatitis up to 4 years (aOR 2.73, 95% CI 1.66-4.49) and also suggested a dose-response relationship. A tendency was observed with asthma between 3 and 6 years (aOR 1.65, 95% CI 0.95-2.86).

CONCLUSIONS

Our findings show positive associations between exposure to antibiotics and allergies, mainly atopic dermatitis and food allergy within the first year of life, after prenatal exposure, and atopic dermatitis and asthma after post-natal exposure to antibiotics in children born in rural settings.

Transition From Phasic to Tonic Contractility in Airway Smooth Muscle After Birth: An Experimental and Computational Modeling Study

Fetal airway smooth muscle (ASM) exhibits phasic contractile behavior, which transitions to a more sustained "tonic" contraction after birth. The timing and underlying mechanisms of ASM transition from a phasic to a tonic contractile phenotype are yet to be established. We characterized phasic ASM contraction in preterm (128 day gestation), term (~150 day gestation), 1-4 month, 1 yr, and adult sheep (5yr). Spontaneous phasic activity was measured in bronchial segments as amplitude, frequency, and intensity. The mechanism of phasic ASM contraction was investigated further with a computational model of ASM force development and lumen narrowing. The computational model comprised a two-dimensional cylindrical geometry of a network of contractile units and the activation of neighboring cells was dependent on the strength of coupling between cells. As expected, phasic contractions were most prominent in fetal airways and decreased with advancing age, to a level similar to the level in the 1-4 month lambs. Computational predictions demonstrated phasic contraction through the generation of a wave of activation events, the magnitude of which is determined by the number of active cells and the strength of cell-cell interactions. Decreases in phasic contraction with advancing age were simulated by reducing cell-cell coupling. Results show that phasic activity is suppressed rapidly after birth, then sustained at a lower intensity from the preweaning phase until adulthood in an ovine developmental model. Cell-cell coupling is proposed as a key determinant of phasic ASM contraction and if reduced could explain the observed maturational changes.

Trimester-specific association between antibiotics exposure during pregnancy and childhood asthma or wheeze: the role of confounding

PURPOSE

We conducted the meta-analysis to respectively evaluate the risk of prenatal antibiotics use during specific trimesters (first, second, and third trimester) on childhood asthma or wheeze and to explore whether the association was biased by potential confounding.

METHODS

The quality of included articles was assessed according to Newcastle-Ottawa Quality Assessment Scale and the Strengthening the Reporting of Observational Studies in Epidemiology. A random effects model was used to calculate pooled risk ratios and corresponding 95% confidence interval (CI), and publication bias was tested by Egger statistical test.

RESULTS

Eight studies were included finally. We found a crude positive association of prenatal antibiotics use during each pregnancy trimester and risk of childhood asthma or wheeze with RRs of 1.28 (95% CI, 1.09-1.51) for the first trimester of pregnancy, 1.25 (95% CI, 1.02-1.52) for the second trimester, and 1.25 (95% CI, 1.05-1.49) for the third trimester. However, when considering potential factors of maternal infections and presence of siblings, the relationship for each trimester was insignificant.

CONCLUSIONS

This systemic review and meta-analysis proposed a crude positive association between prenatal antibiotic use in every specific trimester and risk of childhood asthma or wheeze. However, adjustment for confounders decreased the relative risk estimates, supporting the concept that these associations are, at least in part, because of confounding by indication.

Maternal Cytokine Profiles during Pregnancy Predict Asthma in Children of Mothers without Asthma

Little is known about whether maternal immune status during pregnancy influences asthma development in the child. We measured cytokine production in supernatants from mitogen-stimulated peripheral blood immune cells collected during and after pregnancy from the mothers of children enrolled in the Tucson Infant Immune Study, a nonselected birth cohort. Physician-diagnosed active asthma in children through age 9 and a history of asthma in their mothers were assessed through questionnaires. Maternal production of each of the cytokines IL-13, IL-4, IL-5, IFN-γ, IL-10, and IL-17 during pregnancy was unrelated to childhood asthma. However, IFN-γ/IL-13 and IFN-γ/IL-4 ratios during pregnancy were associated with a decreased risk of childhood asthma (n = 381; odds ratio [OR], 0.33; 95% confidence interval [CI], 0.17-0.66; P = 0.002; and n = 368; OR, 0.36; 95% CI, 0.18-0.71; P = 0.003, respectively). The inverse relations of these two ratios with childhood asthma were only evident in mothers without asthma (n = 309; OR, 0.18; 95% CI, 0.08-0.42; P = 0.00007; and n = 299; OR, 0.17; 95% CI, 0.07-0.39; P = 0.00003, respectively) and not in mothers with asthma (n = 72 and 69, respectively; P for interaction by maternal asthma = 0.036 and 0.002, respectively). Paternal cytokine ratios were unrelated to childhood asthma. Maternal cytokine ratios in mothers without asthma were unrelated to the children's skin-test reactivity, total IgE, physician-confirmed allergic rhinitis at age 5, or eczema in infancy. To our knowledge, this study provides the first evidence that cytokine profiles in pregnant mothers without asthma relate to the risk for childhood asthma, but not allergy, and suggests a process of asthma development that begins in utero and is independent of allergy.

Long-term adverse effects of paracetamol - a review

Paracetamol (acetaminophen) is the most commonly used drug in the world, with a long record of use in acute and chronic pain. In recent years, the benefits of paracetamol use in chronic conditions has been questioned, notably in the areas of osteoarthritis and lower back pain. Over the same period, concerns over the long-term adverse effects of paracetamol use have increased, initially in the field of hypertension, but more recently in other areas as well. The evidence base for the adverse effects of chronic paracetamol use consists of many cohort and observational studies, with few randomized controlled trials, many of which contradict each other, so these studies must be interpreted with caution. Nevertheless, there are some areas where the evidence for harm is more robust, and if a clinician is starting paracetamol with the expectation of chronic use it might be advisable to discuss these side effects with patients beforehand. In particular, an increased risk of gastrointestinal bleeding and a small (~4 mmHg) increase in systolic blood pressure are adverse effects for which the evidence is particularly strong, and which show a degree of dose dependence. As our estimation of the benefits decreases, an accurate assessment of the harms is ever more important. The present review summarizes the current evidence on the harms associated with chronic paracetamol use, focusing on cardiovascular disease, asthma and renal injury, and the effects of in utero exposure.

Meta-analysis of antenatal infection and risk of asthma and eczema

BACKGROUND

The influence of maternal infection during pregnancy on allergic disorders in offspring is not well understood. We performed a systematic review and meta-analysis to evaluate current evidence on the association between maternal infection during pregnancy and asthma or eczema in offspring.

METHODS

We searched databases (PubMed, EMBASE, Medline, and Web of Science) for all relevant studies published before March 2016. Any cohort studies, case-control studies, or cross-sectional studies published in English and focused on the association between maternal infection during pregnancy and the risk of asthma or eczema in offspring were included. Random-effects models were used for combined analyses.

RESULTS

A total of 10 studies with 299,830 participants were included. Maternal infection was associated with an increased risk for asthma (odds ratio [OR]: 1.55; 95% confidence interval [CI]: 1.24-1.92; P < 0.01) and eczema (OR: 1.36; 95% CI: 1.13-1.64; P < 0.01). Further analyses showed associations between asthma and several specific maternal infections: fever episode (OR: 1.73; 95% CI: 1.35-2.23), chorioamnionitis (OR: 1.42; 95% CI: 0.96-2.11), respiratory infection (OR: 1.49; 95% CI: 0.94-2.36), and urogenital infection (OR: 1.39; 95% CI: 1.18-1.64).

CONCLUSION

The results from this meta-analysis and systematic review provide evidence that maternal infection during pregnancy might be related to subsequent asthma and eczema in offspring. However, there was variation of included studies with regard to type of maternal infection, age of children, and methods of exposure ascertainment. Additional studies are needed to further confirm these associations.

The Association between Birth Weight and Gestational Age and Asthma in 6-7- and 13-14-Year-Old Children

Background. Previous studies that assessed the role of birth weight and gestational age in the risk of asthma have been conflicting. Objectives. To examine the association between birth weight and gestational age and symptoms of asthma. Patients and Methods. Subjects were 6656 school children of ages 6-7 and 13-14 years from urban districts of Mazandaran, Iran. ISAAC questionnaires were used. Results. There was an increased risk of "wheeze ever" in both age groups with birth weight under 2.5 kg and in all subgroups of low birth weight (LBW). Birth weight more than 3.5 kg was associated with lower risk of "severe asthma" in age group 6-7 years. With respect to gestational age, higher risks of "wheeze ever," "asthma ever," and "night cough in the past 12 months" were found in age group 13-14 years born before 37 weeks and the risk of "severe asthma" was higher in younger group (6-7 years). A lower risk of "asthma ever" was also found in 6-7-year-old children and 13-14-year-old girls who were born after 40 weeks. Conclusions. This study showed that there is a direct relation between "wheeze ever" and LBW and an inverse relation between risk of "severe asthma" and birth weight more than 3.5 kg.

Paracetamol exposure in pregnancy and early childhood and development of childhood asthma: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

While paracetamol exposure in pregnancy and early infancy has been associated with asthma, it remains unclear whether this is confounded by respiratory tract infections, which have been suggested as an alternative explanation. We undertook a systematic review and meta-analysis of longitudinal studies that reported the association between paracetamol exposure during pregnancy or infancy and the subsequent development of childhood asthma (≥5 years).

METHODS

Two independent researchers searched the databases EMBASE and PUBMED on 12 August 2013 for relevant articles using predefined inclusion and exclusion criteria. Study quality was assessed and results were pooled using fixed effect models or random effect models when moderate between-study heterogeneity was observed. We explicitly assessed whether the observed associations are due to confounding by respiratory tract infections.

RESULTS

Eleven observational cohort studies met the inclusion criteria. Any paracetamol use during the first trimester was related to increased risk of childhood asthma (5 studies, pooled OR=1.39, 95% CI 1.01 to 1.91) but there was marked between-study heterogeneity (I(2)=63%) and only one of these studies adjusted for maternal respiratory tract infections. Increasing frequency of use of paracetamol during infancy was associated with increased odds of childhood asthma (3 studies, pooled OR=1.15, 95% CI 1.00 to 1.31 per doubling of days exposure), but in these same three studies adjusting for respiratory tract infections reduced this association (OR=1.06, 95% CI 0.92 to 1.22).

DISCUSSION

The association during early pregnancy exposure was highly variable between studies and exposure during infancy appears to be moderately confounded by respiratory tract infections. There is insufficient evidence to warrant changing guidelines on early life paracetamol exposure at this time.

Elucidation of pathways driving asthma pathogenesis: development of a systems-level analytic strategy

Asthma is a genetically complex, chronic lung disease defined clinically as episodic airflow limitation and breathlessness that is at least partially reversible, either spontaneously or in response to therapy. Whereas asthma was rare in the late 1800s and early 1900s, the marked increase in its incidence and prevalence since the 1960s points to substantial gene × environment interactions occurring over a period of years, but these interactions are very poorly understood (1-6). It is widely believed that the majority of asthma begins during childhood and manifests first as intermittent wheeze. However, wheeze is also very common in infancy and only a subset of wheezy children progress to persistent asthma for reasons that are largely obscure. Here, we review the current literature regarding causal pathways leading to early asthma development and chronicity. Given the complex interactions of many risk factors over time eventually leading to apparently multiple asthma phenotypes, we suggest that deeply phenotyped cohort studies combined with sophisticated network models will be required to derive the next generation of biological and clinical insights in asthma pathogenesis.

Respiratory viral infections in pregnant women with asthma are associated with wheezing in the first 12 months of life

BACKGROUND

There are few studies investigating the relationship between respiratory viral infection in pregnancy and asthma in the offspring, and none among mothers with asthma. Infants of mothers with asthma are more likely to wheeze and have a higher risk of developing asthma than infants of non-asthmatic mothers.

METHODS

A prospective cohort study of viral infection in pregnancy was conducted between 2007 and 2009, and a subgroup of infants of mothers with asthma was followed up at 6 and 12 months of age. During common colds, nasal and throat swabs were collected from mothers and respiratory viruses detected by polymerase chain reaction. Respiratory health of infants was assessed by parent-completed questionnaire.

RESULTS

Twelve-month-old infants whose mothers had confirmed viral infections in pregnancy (n = 26) reported more frequent wheeze (40% had 4-12 wheeze attacks compared with 0%), sleep disturbed by wheeze (1 night per week or more in 60% vs. 11%), beta agonist treatment for wheeze (27% vs. 0%), prolonged colds (2 wk or longer 31% vs. 0%), more eczema (40% vs. 6.3%), and parent-perceived asthma (32% vs. 0%), compared with infants whose mothers had common colds without laboratory-confirmed viral infection (n = 16).

CONCLUSIONS

This study demonstrates a relationship between maternal respiratory viral infection in pregnancy and wheezing illness in infants of mothers with asthma. Viral infections are the most common cause of asthma exacerbations in pregnancy, and infants of asthmatic mothers are at increased risk of asthma themselves. Further research is needed to elucidate the mechanisms involved.

Systematic review and meta-analyses: fever in pregnancy and health impacts in the offspring

BACKGROUND AND OBJECTIVE

Fever during pregnancy has been suspected to harm the developing fetus. However, until now, no systematic analysis of the available evidence has been undertaken to assess the impact of maternal fever on health outcomes in the child. The goal of this study was to systematically review evidence from epidemiologic studies on adverse health outcomes of the offspring in relation to exposure to maternal fever during pregnancy.

METHODS

Systematic searches in PubMed, Web of Science, and the Cochrane Library were performed by using Medical Subject Headings, Boolean operators, and truncation, and references of references were reviewed. Cohort and case-control studies addressing health outcomes of prenatal fever exposure in humans were eligible for inclusion. Studies with no direct reference to fever, studies in selected populations (eg, preterm births), and studies published before 1990 were excluded.

RESULTS

The available literature supported an increased risk of adverse offspring health in association with fever during pregnancy. The strongest evidence was available for neural tube defects, congenital heart defects, and oral clefts, in which meta-analyses suggested between a 1.5- and nearly 3-fold increased risk with fever exposure in the first trimester. We did not find strong evidence of a dose-response relationship, but there was some evidence that antipyretic medications may have a protective effect when used in relation to febrile episodes.

CONCLUSIONS

We found substantial evidence to support the contention that maternal fever during pregnancy may negatively affect offspring health. The harmful effects seemed to cover both short- and longer-term health outcomes; however, for several outcomes, the evidence was insufficient to judge any association.

Prenatal and childhood infections: implications for the development and treatment of childhood asthma

Bacterial and viral infections occur early and recurrently in life and thereby impose a substantial disease burden. Besides causing clinical symptoms, a potential role of infection in the development of the asthma syndrome later in life has also been suggested. However, whether bacterial and viral infections unmask host factors in children at risk of asthma or whether they directly cause asthma remains unclear; both viewpoints could be justified, but the underlying mechanisms are complex and poorly understood. Recently, the role of the bacterial microbiome has been emphasised. But data are still sparse and future studies are needed for definitive conclusions to be made. In this Review, we discuss present knowledge of viruses and bacteria that infect and colonise the respiratory tract and mucosal surfaces, including their timepoint of action, host factors related to infection, and their effect on childhood asthma. Childhood asthma could be the result of a combination of altered host susceptibility and infectious agents.

The 'Hygiene hypothesis' and the sharp gradient in the incidence of autoimmune and allergic diseases between Russian Karelia and Finland

Autoimmune and allergic diseases have become a major health problem in the Western world during past decades. The hygiene hypothesis suggests that decreased microbial exposure in childhood leads to increasing prevalence of these diseases. This review summarizes epidemiological evidence and current immunological knowledge concerning the hygiene hypothesis. Recent results from Russian Karelia and Finland imply that environmental factors have greatly contributed to the increasing prevalence of immune-mediated disorders. Infections, or lack of them, may indeed be strongly involved in the development of both autoimmune and allergic diseases.

Pregnancy exposures and risk of childhood asthma admission in a population birth cohort

BACKGROUND

There is increasing interest in the potential for in utero exposures to affect the risk of asthma. We used population data to explore the associations between perinatal conditions and the risk of hospital admission with asthma between the 2nd and 5th birthday.

METHODS

The study population was 240,511 singleton infants born during 2001-2003. Birth records and longitudinally linked hospital admissions were used to identify asthma admissions and to model potential risk factors.

RESULTS

A total of 7245 children (3.0%) had one or more childhood admissions with asthma. In utero infectious exposures associated with childhood asthma were maternal antenatal admission with a urinary tract infection (UTI) [adjusted odds ratio (aOR) = 1.49, 95% confidence interval (1.23-1.79)] and pre-term pre-labor rupture of membranes (PROM) [aOR = 1.23 (1.04-1.45)]. There was no evidence that gestational age at time of first antenatal UTI admission (<28, ≥ 28 wks) affected the risk of asthma (homogeneity test p = 0.6). Pre-term birth was a risk factor for asthma admission, with the risk decreasing by 5.3% with each extra week of gestation. Autumn and winter conceptions were associated with an increased risk of childhood asthma admission: winter aOR = 1.15 (1.08-1.23), autumn aOR = 1.09 (1.02-1.16).

CONCLUSIONS

As in utero exposure to both UTI and PROM carry an increased risk of childhood asthma admission, this suggests that the immune system response generally is the relevant factor rather than a specific organism. The season-associated risk is consistent with early pregnancy exposures such as the winter flu season or low vitamin D.

Prenatal or early-life exposure to antibiotics and risk of childhood asthma: a systematic review

CONTEXT

The increasing prevalence of childhood asthma has been associated with low microbial exposure as described by the hygiene hypothesis.

OBJECTIVE

We sought to evaluate the evidence of association between antibiotic exposure during pregnancy or in the first year of life and risk of childhood asthma.

METHODS

PubMed was systematically searched for studies published between 1950 and July 1, 2010. Those that assessed associations between antibiotic exposure during pregnancy or in the first year of life and asthma at ages 0 to 18 years (for pregnancy exposures) or ages 3 to 18 years (for first-year-of-life exposures) were included. Validity was assessed according to study design, age at asthma diagnosis, adjustment for respiratory infections, and consultation rates.

RESULTS

For exposure in the first year of life, the pooled odds ratio (OR) for all studies (N = 20) was 1.52 (95% confidence interval [CI]: 1.30-1.77). Retrospective studies had the highest pooled risk estimate for asthma (OR: 2.04 [95% CI: 1.83-2.27]; n = 8) compared with database and prospective studies (OR: 1.25 [95% CI: 1.08-1.45]; n = 12). Risk estimates for studies that adjusted for respiratory infections (pooled OR: 1.16 [95% CI: 1.08-1.25]; n = 5) or later asthma onset (pooled OR for asthma at or after 2 years: OR: 1.16 [95% CI: 1.06-1.25]; n = 3) were weaker but remained significant. For exposure during pregnancy (n = 3 studies), the pooled OR was 1.24 (95% CI: 1.02-1.50).

CONCLUSIONS

Antibiotics seem to slightly increase the risk of childhood asthma. Reverse causality and protopathic bias seem to be possible confounders for this relationship.

Prenatal paracetamol exposure and asthma: further evidence against confounding

BACKGROUND

Observational studies have reported an association between maternal use of paracetamol in pregnancy and childhood asthma, which was not explained by measured confounding factors. However, it is possible that this relation might be confounded by unmeasured behavioural factors linked to paracetamol usage; if that were the case, effects of similar magnitude of partner's paracetamol use and/or postnatal maternal use would be expected.

METHODS

In the Avon Longitudinal Study of Parents and Children (ALSPAC), a population-based birth cohort, we compared the univariate effects of maternal use of paracetamol in pregnancy on risk of doctor-diagnosed asthma, wheeze and elevated immunoglobulin E (IgE) in the offspring at 7 years of age, with the univariate effects of partner's use and postnatal maternal use on these phenotypes.

RESULTS

Maternal use of paracetamol in pregnancy was strongly associated with all outcomes. Partner's use was very weakly associated with asthma but not associated with wheezing or IgE. Postnatal maternal use was associated with asthma and wheezing, though less strongly than was prenatal use, and was not associated with IgE. On mutual adjustment, the effects of maternal use in pregnancy on all outcomes were not substantially attenuated, whereas the effects of partner's use on asthma, and of postnatal maternal use on asthma and wheezing, were reduced.

CONCLUSIONS

These findings suggest that the relation between maternal use of paracetamol in pregnancy and childhood asthma is unlikely to be confounded by unmeasured behavioural factors linked to paracetamol use.

Antibiotic use in infancy and symptoms of asthma, rhinoconjunctivitis, and eczema in children 6 and 7 years old: International Study of Asthma and Allergies in Childhood Phase III

BACKGROUND

Phase III of the International Study of Asthma and Allergies in Childhood measured the global prevalence of symptoms of asthma, rhinoconjunctivitis, and eczema in children.

OBJECTIVE

To investigate the associations between the use of antibiotics in the first year of life and symptoms of asthma, rhinoconjunctivitis, and eczema in children 6 and 7 years old.

METHODS

Parents or guardians of children 6 and 7 years old completed written questionnaires on current symptoms and possible risk factors. Prevalence odds ratios (ORs) were estimated by using logistic regression.

RESULTS

A total of 193,412 children from 71 centers in 29 countries participated. Reported use of antibiotics in the first year of life was associated with an increased risk of current asthma symptoms (wheezing in the previous 12 months) with an OR (adjusted for sex, region of the world, language, and per capita gross national income) of 1.96 (95% CI, 1.85-2.07); this fell to 1.70 (1.60-1.80) when adjusted for other risk factors for asthma. Similar associations were observed for severe asthma symptoms (OR, 1.82; 95% CI, 1.67-1.98), and asthma ever (OR, 1.94; 95% CI, 1.83-2.06). Use of antibiotics in the first year of life was also associated, but less strongly, with increased risks of current symptoms of rhinoconjunctivitis (OR, 1.56; 95% CI, 1.46-1.66) and eczema (OR, 1.58; 95% CI, 1.33-1.51).

CONCLUSION

There is an association between antibiotic use in the first year of life and current symptoms of asthma, rhinoconjunctivitis, and eczema in children 6 and 7 years old. Further research is required to determine whether the observed associations are causal or are a result of confounding by indication or reverse causation.

Vacuum-assisted delivery is associated with late-onset asthma

BACKGROUND

Perinatal factors during delivery might modulate fetal immunological development and thereby be associated with the development of allergic diseases and asthma later.

METHODS

Perinatal data was recorded during pregnancy and at the time of delivery in regard to 5823 children who were born in Northern Finland in 1985-1986. Data from self-administered questionnaires were available at the ages of 7 and 15-16 years and skin prick tests for four main allergens were carried out at the age of 15-16 years. Only singletons delivered by the vaginal route were analyzed.

RESULTS

There was a higher prevalence of doctor-diagnosed asthma at any time of life among children who were delivered by vacuum extraction (RR 1.80, 95% CI 1.27-2.56; P < 0.001) in comparison with spontaneously delivered children. In particular, this risk was increased as regards late-onset asthma (RR 2.41, 95% CI 1.52-3.81; P < 0.001). Perinatal effects had less impact on the development of other asthma, atopy or hay fever.

CONCLUSIONS

The delivery by vacuum extraction had significant impact on the development of late-onset asthma compared with spontaneously delivered children.

A novel study design to investigate the early-life origins of asthma in children (SAGE study)

This is a description of the Study of Asthma, Genes and the Environment (SAGE), a novel birth cohort created from provincial healthcare administrative records. It is a general population-based cohort, composed of children at high and low risk for asthma, living in urban and rural environments in Manitoba, Canada. The SAGE study captures the complete longitudinal healthcare records of children born in 1995 and contains detailed information on early-life exposures, such as antibiotic utilization and immunization, in relationship to the development of asthma. Nested within the birth cohort is a case-control study, which was created to collect information on home environmental exposures from detailed surveys and home dust sampling, to confirm asthma status in children and use this data to validate healthcare database measures of asthma, to determine differences in immune system responsiveness to innate and adaptive immune stimuli in asthma, to genotype children for genes likely associated with the development of asthma and to study the epigenetic regulation of pre-established protective vs allergic immune responses. The SAGE study is a multidisciplinary collaboration of researchers from pediatric allergy, population health, immunology, and genetic and environmental epidemiology. As such, it serves as a fertile, interdisciplinary training ground for graduate students, and postdoctoral and clinician fellows.

Intrauterine bacterial growth at birth and risk of asthma and allergic sensitization among offspring at the age of 15 to 17 years

BACKGROUND

Microbial colonization of the airways and intestine during birth might have an effect on the risk of asthma and allergic diseases later in life.

OBJECTIVE

We sought to evaluate the association between intrauterine microbial growth at the time of delivery and the development of asthma and allergic sensitization among offspring.

METHODS

Intrauterine bacterial culture results were recorded at the time of cesarean delivery of 460 children who were born at Kuopio University Hospital during 1990-1992. When the children reached the age of 15 to 17 years, self-administered questionnaires were sent to the mothers, and 382 of the children were also examined by using skin prick tests.

RESULTS

Intrauterine growth of potential pathogenic anaerobic bacteria and Streptococcus species at birth was associated with an increased risk of doctor-diagnosed asthma ever (odds ratio [OR], 4.51 [95% CI, 1.56-13.0]; OR, 2.53 [95% CI, 1.19-5.38]) and doctor-diagnosed current asthma (OR, 7.34 [95% CI, 2.44-22.03]; OR, 3.37 [95% CI, 1.46-7.76]) at the age of 15 to 17 years compared with the risk seen in subjects with negative microbial cultures. These findings remained significant also after applying the Bonferroni correction. No significant association after the Bonferroni correction was detected between intrauterine microbial growth and allergic sensitization among offspring.

CONCLUSION

The results of this study indicated that specific intrauterine microbial growth at the time of birth might increase the risk of asthma among offspring through inflammatory mechanisms. These results indicate new potential targets for future studies on the effects of maternal vaginal microflora and intrauterine infection in the development of asthma among children.

Maternal mood scores in mid-pregnancy are related to aspects of neonatal immune function

BACKGROUND

Although there are recognised associations between psychological and immune function, the effects of maternal depressive symptoms on fetal immune development have not been investigated.

METHODS

This study examined the relationship between maternal depression scores as assessed by the Beck Depression Inventory (BDI) in the second trimester and measure of neonatal immune function measured in cord blood. This study was conducted in a cohort of women (n=83) who had received either fish oil containing 3.7 g/day n-3 polyunsaturated fatty acid (n-3PUFA) or a placebo from 20 weeks gestation as part of a randomised controlled trial.

RESULTS

At 20 weeks gestation, prior to the intervention, 22% of women in the study manifested mild to moderate depressive symptoms (BDI > or =10). Neonates of these women had higher lymphoproliferative responses to a range of stimuli (including egg ovalbumin and cat allergen) compared with neonates of women with normal BDI scores (<10). These neonates also showed higher spontaneous cytokine production including (IL-6 and IL-10) and higher stimulated cytokine responses to both bacterial antigens and allergens. These patterns were evident after allowing for maternal age and education, parity, gestation, infant gender, delivery method and neonatal n-3/n-6 PUFA status.

CONCLUSION

This exploratory study supports the notion that maternal mood in pregnancy may have the potential to influence fetal immune development. Further studies are needed to determine the significance of this.

Prenatal factors and the development of asthma

PURPOSE OF REVIEW

There is increasing evidence that both prenatal and perinatal events influence both allergic diseases and early-life respiratory morbidity.

RECENT FINDINGS

Studies in the last year have suggested that in-utero exposures including tobacco smoke exposure, dietary exposures including vitamin D, and prenatal infection and exposure to microbial products may modulate both atopy and respiratory disease. There have been studies revealing gene x environment interactions between inflammatory pathway genes and in-utero smoke exposure. There have also been studies which have revealed that prenatal exposure to endotoxin may be protective. On the other hand, a recent study also suggested that chorioamnionitis may increase the risk of recurrent wheezing in combination with preterm birth. Finally, two separate large cohort studies evaluated maternal diet in pregnancy and suggested that vitamin D levels may be protective against asthma and wheezing.

SUMMARY

There is epidemiological evidence for multiple prenatal factors impacting early-life respiratory morbidity. The mechanisms of these factors need further investigation and may act via various pathways which include effects on lung development, allergic and nonallergic inflammation, and airway remodeling. It remains to be determined if some of these early-life factors which predispose to wheezing will all translate into increased risk of asthma.

Fish oil intake compared with olive oil intake in late pregnancy and asthma in the offspring: 16 y of registry-based follow-up from a randomized controlled trial

BACKGROUND

Evidence suggests that asthma is rooted in the intrauterine environment and that intake of marine n-3 polyunsaturated fatty acids (n-3 PUFAs) in pregnancy may have immunomodulatory effects on the child.

OBJECTIVE

Our aim was to examine whether increasing maternal intake of n-3 PUFAs in pregnancy may affect offspring risk of asthma.

DESIGN

In 1990, a population-based sample of 533 women with normal pregnancies were randomly assigned 2:1:1 to receive four 1-g gelatin capsules/d with fish oil providing 2.7 g n-3 PUFAs (n = 266); four 1-g, similar-looking capsules/d with olive oil (n = 136); or no oil capsules (n = 131). Women were recruited and randomly assigned around gestation week 30 and asked to take capsules until delivery. Among 531 live-born children, 528 were identified in registries and 523 were still alive by August 2006. Diagnoses from the International Coding of Diseases version 10 were extracted from a mandatory registry that recorded diagnoses reported from hospital contacts.

RESULTS

During the 16 y that passed since childbirth, 19 children from the fish oil and olive oil groups had received an asthma-related diagnosis; 10 had received the diagnosis allergic asthma. The hazard rate of asthma was reduced by 63% (95% CI: 8%, 85%; P = 0.03), whereas the hazard rate of allergic asthma was reduced by 87% (95% CI: 40%, 97%; P = 0.01) in the fish oil compared with the olive oil group.

CONCLUSION

Under the assumption that intake of olive oil in the dose provided here was inert, our results support that increasing n-3 PUFAs in late pregnancy may carry an important prophylactic potential in relation to offspring asthma.

Stress and childhood asthma risk: overlapping evidence from animal studies and epidemiologic research

Rapidly expanding evidence increasingly strengthens the evidence linking psychological factors to asthma and allergy expression. Parallel studies in animals and humans demonstrating the influence of prenatal maternal stress and early caregiving experiences on the disrupted regulation of defensive biological systems [eg, sympathetic and adrenomedullary (SAM) system and the hypothalamicpituitary-adrenocortical (HPA) axis] provide strong proof of concept for this line of research. The consequent altered neuroimmune responses may influence the expression of immune-mediated disorders such as asthma as well as enhance an individual's susceptibility to other environmental factors that may also contribute to asthma risk.

Prematurity, chorioamnionitis, and the development of recurrent wheezing: a prospective birth cohort study

BACKGROUND

Prematurity (< 37 weeks) has been inconsistently associated with asthma and wheezing. Chorioamnionitis may promote both prematurity and inflammatory pathways in infants' airways.

OBJECTIVE

To investigate the relationship of prematurity and chorioamnionitis with the development of early childhood recurrent wheezing.

METHODS

The Boston Birth Cohort (n = 1096) were followed prospectively from birth to a mean age of 2.2 +/- 2 years. Perinatal and postnatal clinical data and placental pathology were collected. The primary outcome was recurrent wheezing (> or =2 physician documented episodes). Secondary outcomes included physician-diagnosed asthma, food allergy, and eczema. Preterm children were grouped by gestational age into moderately (33-36.9 weeks) and very preterm (< 33 weeks) with and without chorioamnionitis, and compared with term children without chorioamnionitis (reference group). Chorioamnionitis was diagnosed either by intrapartum fever or by placental histology findings. Logistic regression models were performed to investigate the independent and joint associations of degree of prematurity and chorioamnionitis.

RESULTS

Prematurity was associated with recurrent wheezing (odds ratio [OR], 1.7; 95% CI, 1.2-2.6). However, when subjects were grouped by degree of prematurity with or without chorioamnionitis, the highest risk of wheezing (OR, 4.0; 95% CI, 2.0-8.0) and physician-diagnosed asthma (OR, 4.4; 95% CI, 2.2-8.7) was present in the very preterm children with chorioamnionitis. The effect on both wheezing (OR, 5.4; 95% CI, 2.4-12.0) and asthma (OR, 5.2; 95% CI, 2.3-11.9) was greater in African Americans. Neither prematurity nor chorioamnionitis was associated with food allergy or eczema.

CONCLUSION

We found a strong joint effect of prematurity and chorioamnionitis on early childhood wheezing. This effect was stronger in African American subjects.

Maternal pre-pregnancy obesity and diagnosis of asthma in offspring at age 3 years

OBJECTIVE

The objective of this study was to examine the relationship between maternal pre-pregnancy obesity and a diagnosis of asthma in offspring at age 3 years.

METHODS

A population-based sample of children born in large U.S. cities in 1998-2000 was followed since birth (N=1971). The main outcome measure was whether the mother reported at 3 years that the child had ever been diagnosed with asthma. Multilevel logistic regression models were used to estimate the association between maternal pre-pregnancy obesity and child asthma diagnosis, as well as the extent to which the association can be explained by sociodemographic, medical, obstetric, and behavioral factors associated with both conditions.

RESULTS

Children with obese mothers had 52% higher odds of having an asthma diagnosis by age 3 (OR=1.52; 95% CI: 1.18-1.93). Sociodemographic, medical, obstetric, and behavioral factors explained some, but not all, of the association.

CONCLUSIONS

Maternal pre-pregnancy obesity is associated with diagnosis of asthma in offspring at age 3 years. The results from this study are preliminary and need to be replicated and further explored, but are suggestive of a complex intergenerational linkage between obesity and asthma.

Prenatal maternal stress and early caregiving experiences: implications for childhood asthma risk

There is still much debate as to the pathways through which some children develop asthma and others do not. One possible mechanism outlined here concerns the way in which stress may influence the neuroendocrine system and thence the immune system. Supporting evidence from animal experiments suggests that maternal prenatal stress may be of importance, resulting in programming of the infant's HPA axis. In addition, social stressors during the early part of a child's life may also affect the HPA axis and thence dysregulation of immune system functioning with implications for the development of asthma.

Antenatal steroid therapy and childhood asthma: Is there a possible link?

This paper presents a hypothesis that fetal exposure to corticosteroids is an independent risk factor for the development of asthma in childhood. The prevalence of childhood asthma saw a dramatic rise from the 1980s up until the early 2000s. Among the explanations for the increase in asthma prevalence included interest in exposures arising in the gestational period. Overlapping the time period of the increasing prevalence of childhood asthma is the increased use of antenatal corticosteroid therapy for fetal lung maturation. Through an examination of the published literature, a time dependent association between year of birth (and hence exposure to the antenatal corticosteroids) and the relationship between preterm birth and childhood asthma is noted. A brief review of the trends in the prevalence of asthma, the use of antenatal corticosteroids including their established latent effects and the time dependant association between preterm birth and the risk of childhood asthma are provided.

The influence of maternal respiratory infections during pregnancy on infant lung function

INTRODUCTION

We studied whether maternal respiratory infections during pregnancy adversely influence lung growth and development of the offspring, resulting in poor early life lung function.

METHODS

Infants were participants of the Wheezing Illnesses Study Leidsche Rijn (WHISTLER). Lung function measurements (single occlusion technique) were performed during natural sleep. Questionnaire data were used to obtain information on maternal respiratory infections during pregnancy. Multivariate analysis was conducted to assess the relationship between maternal respiratory infections during pregnancy and resistance and compliance of the respiratory system, adjusting for potential confounding variables.

RESULTS

Lower values of compliance (Crs) were found in infants of mothers with respiratory infections during pregnancy; Crs fell by 5.5% (P = 0.031). The difference in Crs between infants of mothers with and without respiratory infections during pregnancy remained unchanged and statistically significant after adjusting for potential confounding variables. The more respiratory infections the mother experienced during pregnancy, the lower the value of Crs was in her offspring (P for trend = 0.016). Using Crs corrected for body weight the relationship with maternal infections was non-significant, however still showing a trend.

CONCLUSIONS

The results of this study may indicate that mothers who experience respiratory infections during pregnancy have newborns with lower compliance of the respiratory system.

Diet and the developing immune system

Undernutrition during fetal life is known to have programming effects upon tissue morphology and function. This generally promotes poor health in adult life, with increased risk of metabolic syndrome and cardiovascular mortality noted among individuals whose growth was constrained in utero. Undernutrition in early life impacts upon the development of the immune organs and appears to diminish cellular immunity and increase the risk of atopic disorders during childhood. A limited body of evidence implicates fetal programming in the development of autoimmune disorders. This area represents an interesting target for further research and preventive medicine.

Antenatal risk factors, cytokines and the development of atopic disease in early childhood

Atopic diseases are complex entities influenced by an array of risk factors, including genetic predisposition, environmental allergens, antenatal exposures, infections and psychosocial factors. One proposed mechanism by which these risk factors contribute to the development of atopic disease is through changes in the production of T helper cell type 1 (Th1) and T helper cell type 2 (Th2) cytokines. The objectives of this review are to discuss antenatal exposures that are associated with paediatric atopic diseases, to discuss the influence of the intrauterine environment on neonatal immune responses, to provide an overview of the Th1 and Th2 pathways and how they relate to atopic disease, and to summarise our current understanding of the association between cytokine responses in cord blood and the development of atopic disease in early childhood.

Maternal testosterone in pregnancy and atopic outcomes in childhood

BACKGROUND

In mice, androgens downregulate Th2 cytokine responses, but whether androgen levels during pregnancy might influence the development of allergy in the offspring has not been studied.

METHODS

In the Avon Longitudinal Study of Parents and Children (ALSPAC), a population-based birth cohort of 14 541 pregnancies, we related maternal blood total testosterone during pregnancy, measured in a subset of the cohort, to allergic outcomes in the offspring, including asthma, hayfever, eczema (n=543) and wheezing (n=532) at 69-81 months, and atopy (positive skin prick test to Dermatophagoides pteronyssinus, cat or grass, n=386) and blood total immunoglobulin E (IgE; n=314) at 7 years. We used logistic and linear regression to analyse binary outcomes and log-transformed IgE, respectively, controlling for potential confounders.

RESULTS

Maternal testosterone was negatively associated with total IgE in boys [adjusted geometric mean ratio (GMR), per doubling of testosterone, 0.33 (0.20-0.55), P=0.000038 (n=168)], but not in girls [GMR 1.04 (0.53-2.06), P=0.91 (n=146)], P-value interaction 0.0086. The effect in boys was even stronger in the absence of maternal atopic disease. Testosterone was not associated with skin test positivity or atopic disease in either sex.

CONCLUSIONS

Higher testosterone levels in pregnancy are associated with lower IgE production in boys.

Can allergic diseases be prevented prenatally?

Allergic diseases continue to increase in prevalence, and now affect over a third of the population in many countries. There is evidence that the increase in such diseases has its origins in early life exposures. Pregnancy or early childhood may therefore be critical periods for preventing the onset of allergic disease, and prenatal interventions are an attractive possibility for a population-based preventive approach. Here we review the data suggesting that prenatal exposures are important in the development of allergic disease, and that interventions during this time might be effective in prevention. We find evidence from both animal and human studies that prenatal interventions can influence the future development of allergic disease. There are a number of mechanisms through which such interventions may act to prevent allergic sensitization. We conclude that prenatal interventions have the potential to reduce the burden of allergic disease, and merit continued investigation. Further research in this area may lead to significant public health initiatives.

Maternal complications and procedures in pregnancy and at birth and wheezing phenotypes in children

RATIONALE

There is increasing interest in the potential influence of fetal and early life conditions on childhood wheezing.

OBJECTIVES

To investigate the associations between maternal complications and procedures in pregnancy and at birth and the risk of various wheezing phenotypes in young children.

METHODS

We studied 15,609 children, aged 6-7 yr, enrolled in a population-based study. Standardized questionnaires were completed by the children's mothers.

RESULTS

Of the children, 9.5% (1,478) had transient early wheezing, 5.4% (884) had persistent wheezing, and 6.1% (948) had late-onset wheezing. Maternal hypertension or preeclampsia was associated with an increased risk of all three wheezing phenotypes (for transient early wheezing: odds ratio [OR], 1.40; 95% confidence interval [95% CI], 1.08-1.82; for persistent wheezing: OR, 1.59; 95% CI, 1.15-2.19; and for late-onset wheezing: OR, 1.47; 95% CI, 1.06-2.01). Use of antibiotics for urinary tract infections was associated with transient early wheezing (OR, 1.52; 95% CI, 1.16-2.00), whereas antibiotic administration at delivery was associated with both transient early wheezing (OR, 1.21; 95% CI, 1.01-1.46) and persistent wheezing (OR, 1.39; 95% CI, 1.10-1.75). Children who had a mother with diabetes were also more likely to have persistent wheezing (OR, 1.72; 95% CI, 0.99-3.00). Neither amniocentesis/chorionic villus sampling, nor weight gain in pregnancy, nor cesarean section was associated with the subsequent development of wheezing. Maternal asthma or atopy was not an effect modifier of the associations found.

CONCLUSIONS

Some maternal complications during pregnancy and at delivery may increase the risk of developing different phenotypes of wheezing in childhood.

Are influences during pregnancy associated with wheezing phenotypes during the first decade of life?

AIM

Recently, attention has focused on possible early life origins for asthma. We sought to identify whether factors present during pregnancy were associated with development of childhood wheezing phenotypes.

METHODS

A whole population birth cohort (n=1456) on the Isle of Wight, UK, was followed through to age 10 y. Where possible, information regarding environmental exposures and events during pregnancy was obtained from the maternity records (n=1238). Children were seen at ages 1, 2, 4 and 10 y, and wheezing symptoms were used to define wheezing phenotypes in the first decade (n=1034).

RESULTS

Risk of early-onsetpersistent wheeze (onset in the first 4 y, still present at age 10) was increased by environmental tobacco smoke exposure in pregnancy (OR=2.44; 95% CI: 1.37-4.34) plus maternal asthma (3.57; 1.84-6.94), but reduced by cat ownership (0.30; 0.13-0.62). Early transient wheeze (onset in the first 4 y, but not present at age 10) was increased by environmental tobacco smoke exposure (1.58; 1.02-2.45), male gender (1.68; 1.09-2.60) and low birthweight (3.65; 1.27-10.52). No environmental factors in pregnancy were associated with late-onset persistent wheeze (onset after age 4 y, still present at 10 y).

CONCLUSION

In addition to genetics, maternal exposures during pregnancy show association with childhood and especially early-life wheezing phenotypes.

Prenatal paracetamol exposure and risk of asthma and elevated immunoglobulin E in childhood

BACKGROUND

We recently found that paracetamol (acetaminophen) use in late pregnancy was associated with an increased risk of early wheezing in the offspring.

OBJECTIVE

To see whether use of paracetamol in late pregnancy is associated with an increased risk of asthma, wheezing and other atopic outcomes in the child at school age.

METHODS

In the population-based Avon Longitudinal Study of Parents and Children, we measured associations of paracetamol and aspirin use in late pregnancy (20-32 weeks) with asthma, hayfever, eczema (n = 8511) and wheezing (8381) in the offspring at 69-81 months, and with atopy (positive skin prick test to Dermatophagoides pteronyssinus, cat or grass, n = 6527) and blood total IgE (n = 5148) at 7 years. We used logistic and linear regression to analyse binary outcomes and log-transformed IgE, respectively, controlling for potential confounders.

RESULTS

Use of paracetamol, but not aspirin, in late pregnancy was positively associated with asthma (odds ratios (ORs), comparing children whose mothers took paracetamol 'sometimes' and 'most days/daily' with those whose mothers never took it, 1.22 (95% confidence interval (CI): 1.06-1.41) and 1.62 (95% CI: 0.86-3.04), respectively; P trend = 0.0037), wheezing (ORs 1.20 (95% CI: 1.02-1.40) and 1.86 (95% CI: 0.98-3.55), respectively; P trend = 0.011), and total IgE (geometric mean ratios 1.14 (95% CI: 1.03-1.26) and 1.52 (95% CI: 0.98-2.38), respectively; P trend = 0.0034), but not hayfever, eczema or skin test positivity. The proportion of asthma attributable to paracetamol use in late pregnancy, assuming a causal relation, was 7%.

CONCLUSION

Paracetamol exposure in late gestation may cause asthma, wheezing and elevated IgE in children of school age.

Infections, medication use, and the prevalence of symptoms of asthma, rhinitis, and eczema in childhood

BACKGROUND

The "hygiene hypothesis" postulates that infections during infancy may protect against asthma and atopy. There is also some evidence that antibiotic and/or paracetamol use may increase the risk of asthma.

METHODS

The study measured the association between infections, and medication use early in life and the risk of asthma at age 6-7 years. It involved 1584 children who had been notified to public health services with serious infections at age 0-4 years, and 2539 children sampled from the general population. For both groups, postal questionnaires were completed by parents.

RESULTS

There was little difference in the prevalence of current wheezing between the childhood infections group (prevalence = 23.5%) and the general population group (prevalence = 24.3%). There was also little difference whether the major site of infection was gastrointestinal (prevalence = 24.1%), invasive (prevalence = 24.6%) or respiratory (prevalence = 21.1%). However, in both groups, there were associations with antibiotic (OR = 1.78, 95% CI 1.49 to 2.14) or paracetamol (OR = 1.38, 95% CI 1.04 to 1.83) use in the first year of life or recent paracetamol use (OR = 2.10, 95% CI 1.78 to 2.49) and current wheezing. There was a weak protective effect of childhood infections in children who had not used antibiotics in the first year of life (OR = 0.78, 95% CI 0.55 to 1.10).

CONCLUSIONS

These findings are consistent with other evidence that antibiotic use early in life may increase the risk of asthma. They are also consistent with some preliminary evidence associating paracetamol use with an increased risk of asthma. Any protective effect of notifiable childhood infections was weak.