Risk factors for atopic dermatitis in New Zealand children at 3.5 years of age

Antibiotics and allergic disorders in childhood

AIM

This paper explores the possible association between antibiotics prescribed in infancy and allergic disorders, mainly eczema and asthma, in childhood.

BACKGROUND

No-one fully understands why childhood asthma and eczema have become so common. Some authorities suggest that there may be an association between eczema and asthma and antibiotics prescribed in childhood; however, others disagree. METHOD/EVALUATION: The available literature was reviewed to examine the links between prescribed antibiotics and childhood eczema and asthma. FINDINGS/KEY ISSUE: Some, but not all, research indicates that antibiotic administration in pregnancy, childbirth or infancy may be linked to childhood asthma and eczema, but much uncertainty remains. None of the papers identified stated the doses of antibiotics prescribed. In addition, we were unable to locate studies reporting the interactions between antibiotics and the developing immune system.

CONCLUSION

Health care professionals should be selective when prescribing antibiotics. Further prospective work is needed to guide the prescribing of antibiotics in childbirth and infancy.

Environmental factors influencing the prevalence of respiratory diseases and allergies among schoolchildren in Chiang Mai, Thailand

Air quality has seriously deteriorated as a consequence of population growth and urbanisation and respiratory diseases increased among residents of urban areas in Chiang Mai Province, Thailand. An International Study of Asthma and Allergies in Childhood (ISAAC) study was conducted among children attending schools located in the selected sites to assess the potential impacts of air pollution on health. The results showed that the prevalence of asthma was similar in all of the schools (approximately 5%; p = 1.000) but that the prevalence of rhinitis [24.3% (CI = 19.4-30.1) vs. 15.7% (CI = 10.3-23.0); p = 0.029] and atopic dermatitis [12.5% (CI = 9.1-16.8) vs. 7.2% (CI = 3.7-12.6); p = 0.093)] was higher in the urban schools, which were exposed to more pollution. Logistic regression analysis identified factors that may be involved, including air pollution, some components of the diet and contact with animals.

Effects of early nutritional interventions on the development of atopic disease in infants and children: the role of maternal dietary restriction, breastfeeding, timing of introduction of complementary foods, and hydrolyzed formulas

This clinical report reviews the nutritional options during pregnancy, lactation, and the first year of life that may affect the development of atopic disease (atopic dermatitis, asthma, food allergy) in early life. It replaces an earlier policy statement from the American Academy of Pediatrics that addressed the use of hypoallergenic infant formulas and included provisional recommendations for dietary management for the prevention of atopic disease. The documented benefits of nutritional intervention that may prevent or delay the onset of atopic disease are largely limited to infants at high risk of developing allergy (ie, infants with at least 1 first-degree relative [parent or sibling] with allergic disease). Current evidence does not support a major role for maternal dietary restrictions during pregnancy or lactation. There is evidence that breastfeeding for at least 4 months, compared with feeding formula made with intact cow milk protein, prevents or delays the occurrence of atopic dermatitis, cow milk allergy, and wheezing in early childhood. In studies of infants at high risk of atopy and who are not exclusively breastfed for 4 to 6 months, there is modest evidence that the onset of atopic disease may be delayed or prevented by the use of hydrolyzed formulas compared with formula made with intact cow milk protein, particularly for atopic dermatitis. Comparative studies of the various hydrolyzed formulas also indicate that not all formulas have the same protective benefit. There is also little evidence that delaying the timing of the introduction of complementary foods beyond 4 to 6 months of age prevents the occurrence of atopic disease. At present, there are insufficient data to document a protective effect of any dietary intervention beyond 4 to 6 months of age for the development of atopic disease.

Prevalence and risk factors for atopic dermatitis in preschool children

BACKGROUND

Atopic dermatitis (AD) is a common condition in infancy which usually disappears by 3 years of age in a significant proportion of children. The prognosis is mostly determined by severity and presence of atopic sensitization.

OBJECTIVES

To investigate prevalence of AD, comorbidities and risk factors in a population of preschool children aged 3-5 years.

METHODS

Children in kindergartens were evaluated. The International Study of Asthma and Allergies in Childhood written questionnaire (WQ) was used, with additional questions on risk factors. Atopy was investigated by skin prick tests.

RESULTS

One thousand, four hundred and two valid WQs (92% response rate) were returned for evaluation. The prevalence of AD symptoms in the last 12 months in the whole population was 18.1% (254 cases). Seventy-two per cent of these children presented AD-specific localizations. The prevalence of eczema as a doctor's diagnosis in the total population was 15.4%. Positive atopic sensitization was present in 18.6% of the total and in 32.2% of the AD study population, respectively. Multiple sensitivities were observed in 58.2% of sensitized children. The prevalence of sensitization demonstrated that the most common sensitizing allergens in children with AD were mites and grass pollen. Rhinitis symptoms and wheezing were present in 32.2% and 24.2%, respectively, of children with AD. Allergic sensitization to egg, cat, grass pollen and mites, as well as the presence of symptoms of rhinitis, and a positive family history of atopy were all significant risk factors for AD.

CONCLUSIONS

The study demonstrates a high prevalence of AD and a close relationship with rhinitis symptoms. Significant risk factors for AD were sensitization to food or inhalant allergens as well as parental history of atopy.

Environmental factors and allergic disorders

Despite numerous studies on possible associations between environmental exposure and allergic disorders, any conclusions made remain a matter of controversy. We conducted a review of evidence in relation to environmental and nutritional determinants and wheeze, asthma, atopic dermatitis, and allergic rhinitis. Identified were 263 articles for analysis after consideration of 1093 papers that were published since 2000 and selected by electronic search of the PubMed database using keywords relevant to epidemiological studies. Most were cross-sectional and case-control studies. Several prospective cohort studies revealed inconsistent associations between various environmental factors and the risk of any allergic disorder. Therefore, the evidence was inadequate to infer the presence or absence of a causal relationship between various environmental exposures and allergic diseases. However, evidence is suggestive of positive associations of allergies with heredity. Because almost all the studies were performed in Western countries, the application of these findings to people in other countries, including Japan, may not be appropriate. Further epidemiological information gained from population-based prospective cohort studies, in particular among Japanese together with other Asians, is needed to assess causal relationships between various environmental factors and allergic diseases.

Defining a role for ambient TLR ligand exposures in the genesis and prevention of allergic diseases

Environmental variables responsible for the increasing allergic disease burden observed in developed countries over the last century have yet to be adequately characterized. Meta-analyses of epidemiological studies presented in the first half of this paper demonstrate a correlation between farm-associated exposures (i.e., livestock, pets, unpasteurized milk, and endotoxin) and a reduction in allergic risk during childhood. Laboratory investigations discussed in the second half of the paper characterize the intrinsic immunostimulatory activities of living environments. Considered together, experimental findings presented herein suggest a novel paradigm by which early life home exposures to microbial products and other allergen-nonspecific immunostimulants modify allergic risk.

Early exposure to pets: good or bad?

Although pet exposure is known to trigger or worsen allergy symptoms and asthma in patients sensitized to pets, data from recent years has shown that pet exposure in early childhood may actually prevent the development of allergic sensitization and allergic diseases including allergic rhinitis, asthma, and atopic dermatitis. The concept of a protective pet effect remains controversial because these findings have not been duplicated in all studies. Moreover, some studies suggest that pet exposure promotes allergic disease. The protective pet effect may be influenced by multiple factors including type of pet; timing, duration, and intensity of exposure; and genetic factors. The mechanisms behind the protective pet effect remain under investigation but may include alterations in immune development, pet-specific tolerance, and exposure to innate immune stimuli.

Effect of prolonged and exclusive breast feeding on risk of allergy and asthma: cluster randomised trial

OBJECTIVE

To assess whether exclusive and prolonged breast feeding reduces the risk of childhood asthma and allergy by age 6.5 years.

DESIGN

Cluster randomised trial.

SETTING

31 Belarussian maternity hospitals and their affiliated polyclinics.

PARTICIPANTS

A total of 17,046 mother-infant pairs were enrolled, of whom 13,889 (81.5%) were followed up at age 6.5 years.

INTERVENTION

Breastfeeding promotion intervention modelled on the WHO/UNICEF baby friendly hospital initiative.

MAIN OUTCOME MEASURES

International study of asthma and allergies in childhood (ISAAC) questionnaire and skin prick tests of five inhalant antigens.

RESULTS

The experimental intervention led to a large increase in exclusive breast feeding at 3 months (44.3% v 6.4%; P<0.001) and a significantly higher prevalence of any breast feeding at all ages up to and including 12 months. The experimental group had no reduction in risks of allergic symptoms and diagnoses or positive skin prick tests. In fact, after exclusion of six sites (three experimental and three control) with suspiciously high rates of positive skin prick tests, risks were significantly increased in the experimental group for four of the five antigens.

CONCLUSIONS

These results do not support a protective effect of prolonged and exclusive breast feeding on asthma or allergy.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN37687716 [controlled-trials.com].

Risk factors for asthma at 3.5 and 7 years of age

BACKGROUND

It has been suggested that factors in early life including exposure to allergens and microbes may influence the development of asthma.

OBJECTIVE

To identify risk factors for asthma in early childhood. Methods Eight-hundred and seventy-one children of European mothers were enrolled at birth, of whom 385 (44.2%) were born small for gestational age (SGA) and 486 were appropriate for gestational age (AGA). Data were collected at birth, 12 months, 3.5 years of age (y) and 7 y. The outcome of interest (current wheeze) was defined as a positive response to the question: 'Has your child had wheezing or whistling in the chest in the last 12 months?'

RESULTS

Participation rate was 85.4% at 1 y, 63.1% at 3.5 y and 68.0% at 7 y. The prevalence of asthma was 23.8% at 3.5 y and 18.1% at 7 y. Antibiotic use in the first year of life and day care in the first year of life were associated with increased risk of wheeze at 7 y [odds ratio (OR)=4.3 95% confidence interval (CI) (1.8-10.1) and OR=2.8 95% CI (1.2-6.5), respectively], but not at 3.5 y. Exposure to dogs was a risk factor for asthma at both ages [OR=2.1 95% CI (1.1-3.8)] as was sleeping on a used cot mattress in the first year of life [OR=1.8 95% CI (1.0-3.2)].

CONCLUSIONS

There was a significant association between antibiotic use and day care in the first year of life and wheezing at 7 y but not at 3.5 y. This strengthens the argument that these factors increase the risk of asthma. We have also made the novel observation that sleeping on a used mattress in the first year of life is a risk factor for wheezing at 3.5 and 7 y. Capsule summary This prospective study of 871 children made the novel observation that sleeping on a used mattress in the first year of life was a risk factor for wheezing at 3.5 and 7 y.

The prevalence of atopic triad in children with physician-confirmed atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is often associated with comorbidities such as allergic rhinitis and asthma.

OBJECTIVE

We sought to describe the frequency of these comorbidities in children with AD.

METHODS

We conducted a cross-sectional study of the first 2270 children with physician-confirmed AD enrolled in a large postmarketing cohort. All were queried for information on comorbidities using a questionnaire from the International Study of Asthma and Allergies in Childhood.

RESULTS

In all, 71.3% reported at least one additional form of atopy (symptoms of asthma or allergic rhinitis). A total of 33.3% reported only symptoms of asthma or allergic rhinitis whereas 38.0% reported symptoms of asthma and allergic rhinitis. By age 3 years, nearly 66% reported at least one additional form of atopy. A statistically significant trend toward poorer disease control was observed for those with additional atopic illnesses (P < .001).

LIMITATIONS

This is a cross-sectional study.

CONCLUSION

Individuals with AD exhibit a predisposition to additional atopic illnesses by age 3 years and in turn the presence of these illnesses correlates with poor disease control.

Cross-sectional study of allergic disorders associated with breastfeeding in Japan: the Ryukyus Child Health Study

Uncertainties remain as to whether breastfeeding is protective against childhood allergic disorders. Positive relationships of breastfeeding with asthma and atopic eczema were observed in two previous Japanese studies. This cross-sectional study investigated the association between the feeding pattern after birth and the prevalence of allergic disorders during the past 12 months in Japanese schoolchildren. Study subjects were 24,077 children aged 6-15 yr in Okinawa. The outcomes were based on diagnostic criteria from the International Study of Asthma and Allergies in Childhood. Allowance was made for age, sex, number of siblings, smoking in the household, paternal and maternal history of asthma, atopic eczema, and allergic rhinitis, and paternal and maternal educational level. Breastfeeding, regardless of exclusivity, for 13 months or longer and exclusive breastfeeding for 4-11 months were independently associated with a higher prevalence of atopic eczema, particularly among children without a parental allergic history. A clear positive dose-response relationship was observed between prolonged duration of breastfeeding, regardless of exclusivity, but not exclusive breastfeeding, and the prevalence of atopic eczema. We found a significant positive trend for atopic eczema across the three categories (formula milk, partial and exclusive breastfeeding) in the first 4 months of life although the odds ratio for exclusive breastfeeding was not statistically significant. No material association was found between the feeding pattern after birth and the prevalence of wheeze or allergic rhinoconjunctivitis. Prolonged breastfeeding may be associated with a higher prevalence of atopic eczema in Japanese children.

Is breast feeding a risk factor for eczema during the first year of life?

Breast feeding (BF) provides many advantages to the offspring; however, at present there is an ongoing debate as to whether or not it prevents allergic diseases. The aim of the current study was to investigate the effect of duration of BF on eczema in the first year of life. A birth cohort of 1128 infants was followed prospectively from 5 months of pregnancy. Data were collected using questionnaires, a medical examination and blood tests for allergy at the age of 1 yr. Breast feeding was not statistically significant associated with eczema in the first year of life [adj ORs with 95% CIs: 0.8 (0.4-1.3), 0.8 (0.5-1.3) and 1.0 (0.6-1.5) for BF duration of 1-6 wk, 7-12 wk and > or = 13 wk, respectively]. Eczema was positively associated with atopy and educational level of the mother, use of antibiotics in pregnancy and passive smoking by the child during the first 12 months. Regular postnatal contact of the infants with dogs was inversely associated with eczema. Breast feeding was positively associated with eczema among children with non-atopic parents [adj ORs with 95% CIs: 2.1 (0.4-10.6), 2.2 (0.4-11.3) and 1.9 (0.4-8.5) for BF duration of 1-6 wk, 7-12 wk and > or = 13 wk, respectively], whereas an inverse association was found among children with atopic parents [adj ORs with 95% CIs: 0.6 (0.3-1.3), 0.7 (0.3-1.4) and 0.9 (0.5-1.7) for the same BF durations]. However, these associations were not statistically significant. Breast feeding has no significant effect on the prevalence of eczema in the first year of life. The effect of BF on eczema in children depends on parental atopy.

Advances in our understanding of the biology of human milk and its effects on the offspring

There is an intense interest in the effects of breast-feeding on the offspring and in understanding the mechanisms behind these effects. More than 50 papers are published monthly on topics such as the influence of breast-feeding on aspects of growth, immune-related effects, mental development, and noncommunicable diseases. Most breast-feeding data are observational; confounding can be difficult to rule out because some maternal factors are associated with both breast-feeding and infant outcomes (e.g., obesity and mental development). The most important short-term immunological benefit of breast-feeding is the protection against infectious diseases. There is also some evidence of lower prevalence of inflammatory bowel diseases, childhood cancers, and type I diabetes in breast-fed infants, suggesting that breast-feeding influences the development of the infant's own immune system. One of the most consistent findings of breast-feeding is a positive effect on later intelligence tests with a few test points advantage for breast-fed infants. In the last few years, several systematic reviews and meta-analyses have examined the effect of breast-feeding on noncommunicable diseases. There seems to be a small protective effect against later overweight and obesity. Blood pressure and blood cholesterol seem to be slightly lower in breast-fed infants; however, the few studies examining breast-feeding and the risk of coronary heart disease in later life did not find an association. Recent data have suggested that breast-feeding can program the insulin-like growth factor-I axis, as 3 studies found that breast-fed infants are taller as adults.

Breastfeeding and infant eczema in the first year of life in the KOALA birth cohort study: a risk period-specific analysis

OBJECTIVE

We studied the association between breastfeeding and eczema, taking into account the possible influence of reverse causation, with risk period-specific analyses.

METHODS

Information on breastfeeding, determinants, and outcomes at 1 year of age was collected with repeated questionnaires for 2405 mother-infant pairs participating in the KOALA (Child, Parent and Health: Lifestyle and Genetic Constitution [in Dutch]) birth cohort study. By using multivariate logistic regression analysis, we compared an overall analysis with risk period-specific analyses.

RESULTS

By the age of 1 year, 535 infants (22.2%) had developed eczema. In an overall analysis, we found a weak nonsignificant trend toward a reduced risk of eczema in the first year of life with increasing duration of breastfeeding (lowest risk for those breastfed for > or = 7 months versus never breastfed). In the risk period-specific analysis (confined to infants "at risk" for eczema onset after 3 months of age), no indication for reverse causation was found (results were not very different, compared with the overall analysis). Infants who were breastfed from birth on had a slightly (although not statistically significantly) increased risk for eczema in the first 3 months of life, compared with infants who were formula fed from birth on.

CONCLUSIONS

Our results indicated that no strong effect of breastfeeding on eczema in the first year of life was present. This conclusion was strengthened by risk period-specific analysis, which made the influence of reverse causation unlikely.

Vaccines, antibiotics, and atopy

PURPOSE

Early exposure to vaccines and antibiotics may increase the risk of developing atopy by protecting against infectious agents and reducing duration and severity of infections (the hygiene hypothesis). It may also shift the developing immune system towards a more allergic response. We assess possible associations in young allergy clinic patients.

METHODS

We conducted a case-control study of 6- to 16-year-old new allergy clinic patients who were skin tested for inhalant allergens during 1987-2001 and enrolled in KPNW since birth (n = 1074). Atopic cases had positive tests for at least one inhalant allergen. Non-atopic controls had negative tests for all inhalant allergens. Using logistic regression analysis, we estimated atopy odds ratios for vaccine and antibiotic exposure variables and associations between vaccine and antibiotic exposures during the first 2 years of life and subsequent new allergy diagnoses.

RESULTS

Atopy was not significantly associated with numbers of vaccine and antigen doses, or number of different antigens during the first 2 years of life. Number of antibiotic prescriptions was negatively associated with atopy risk. Neither exposure was significantly associated with risk of new allergy diagnoses in atopic children.

CONCLUSIONS

Atopy development appears to be unrelated to early vaccine exposure. Frequency of antibiotic prescriptions during early life, a proxy for infection frequency, appears to protect against allergic sensitization. Neither vaccines nor antibiotics appear to induce subsequent allergic reactions in atopic children.

Atopic eczema in children: another harmful sequel of divorce

BACKGROUND

Different lifestyle factors seem to be associated with the risk for atopic diseases and some studies suggest that stress increases the risk of allergic sensitization, asthma and atopic eczema. Only few studies have investigated the association of early stressful life events and atopic eczema (AE) in children.

SUBJECTS AND METHODS

Parents of participants of the ongoing LISA birth cohort study were asked to give information on life events, such as severe disease or death of a family member, unemployment, or divorce of the parents. Lifetime prevalence of AE and incidence after the assessment period for life events were compared.

RESULTS

Prevalence of AE until the age of 4 years was 21.4%. Reported life events within the first 2 years were: severe disease (17.5%) or death (8.4%) of a family member, divorce/separation (3.4%), and unemployment (2.7%). Divorce/separation was associated with a significantly [odds ratio (OR) 3.59, 95% confidence interval (CI) 1.69-7.66] increased and disease with a significantly (OR 0.29, 95% CI 0.13-0.68) decreased incidence of AE for the subsequent 2 years of life. No effect was seen for unemployment.

CONCLUSIONS

Divorce/separation of the parents and severe disease of a family member influence the risk of developing AE.

Atopic eczema: what's new?

Atopic eczema (AE) is a chronic inflammatory skin disease characterized by recurrent intense pruritus and a typical age-related distribution of skin lesions. Several new aspects with regard to the pathogenetic background as well as strategies for prevention, diagnosis and treatment of AE have emerged. There are ongoing studies on genetic susceptibility loci, as well as environmental and nutritional factors associated with an increase or a decrease of AE lesions. The atopy patch test is now available for identification of allergens in aeroallergen-triggered AE. New topical therapies, such as the calcineurin inhibitors, have broadened the therapeutic armamentarium substantially. In order to increase knowledge and coping strategies, patient education programs have been launched. Learning objective Upon completing this paper, the reader should be aware of new developments in AE, especially on nomenclature, prevention strategies, diagnostic tests, as well as therapeutic options.

Diagnosis and treatment of atopic dermatitis in children and adults: European Academy of Allergology and Clinical Immunology/American Academy of Allergy, Asthma and Immunology/PRACTALL Consensus Report

There are remarkable differences in the diagnostic and therapeutic management of atopic dermatitis practiced by dermatologists and pediatricians in different countries. Therefore, the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology nominated expert teams who were given the task of finding a consensus to serve as a guideline for clinical practice in Europe as well as in North America. The consensus report is part of the PRACTALL initiative, which is endorsed by both academies.

Breast feeding and future health

PURPOSE OF REVIEW

This review discusses the long-term health effects of breast feeding, based on the most relevant publications from the second half of 2004 and 2005.

RECENT FINDINGS

The positive effect of breast feeding on later cognitive function continues to be the most consistent and important effect. Also, breast feeding is likely to protect against some immune-related diseases later in life, such as type 1 diabetes, coeliac disease, inflammatory bowel diseases and perhaps cancer. The evidence for an effect on allergic disease continues to be inconclusive. Furthermore, breast feeding seems to be associated with a lower blood pressure and serum cholesterol, but there is no clear association with cardiovascular disease or death. Most new studies and meta-analyses show a protective effect against later obesity, but this seems to be small. A new hypothesis suggests that breast feeding programmes the insulin-like growth factor axis and results in higher growth velocity later in childhood.

SUMMARY

Evidence is increasing that breast feeding, beyond its well-established beneficial effects during the breast-feeding period, also confers long-term benefits. These effects are not strong at the individual level, but are likely to be of importance at the population level. Since the majority of the studies are observational, however, it is difficult to prove causality.

Optimal duration of exclusive breastfeeding

BACKGROUND

: Although the health benefits of breastfeeding are widely acknowledged, opinions and recommendations are strongly divided on the optimal duration of exclusive breastfeeding. Much of the debate has centered on the so-called 'weanling's dilemma' in developing countries: the choice between the known protective effect of exclusive breastfeeding against infectious morbidity and the (theoretical) insufficiency of breast milk alone to satisfy the infant's energy and micronutrient requirements beyond four months of age. The debate over whether to recommend exclusive breastfeeding for four to six months versus 'about six months' has recently become heated and acrimonious.

OBJECTIVES

: The primary objective of this review was to assess the effects on child health, growth, and development, and on maternal health, of exclusive breastfeeding for six months versus exclusive breastfeeding for three to four months with mixed breastfeeding (introduction of complementary liquid or solid foods with continued breastfeeding) thereafter through six months. A secondary objective was to assess the child and maternal health effects of prolonged (greater than six months) exclusive breastfeeding versus exclusive breastfeeding for six months followed by mixed breastfeeding thereafter.

SEARCH STRATEGY

: Two independent literature searches were carried out, together comprising the following databases: MEDLINE (as of 1966), Index Medicus (prior to 1966), CINAHL, HealthSTAR, BIOSIS, CAB Abstracts, EMBASE-Medicine, EMBASE-Psychology, Econlit, Index Medicus for the WHO Eastern Mediterranean Region, African Index Medicus, Lilacs (Latin American and Caribbean literature), EBM Reviews-Best Evidence, the Cochrane Database of Systematic Reviews (The Cochrane Library Issue 3, 2000), and the Cochrane Controlled Trials Register (The Cochrane Library Issue 3, 2000). No language restrictions were imposed. The two searches yielded a total of 2,668 unique citations. Contacts with experts in the field yielded additional published and unpublished studies.

SELECTION CRITERIA

: We selected all internally-controlled clinical trials and observational studies comparing child or maternal health outcomes with exclusive breastfeeding for six or more months versus exclusive breastfeeding for at least three to four months with continued mixed breastfeeding until at least six months. Studies were stratified according to study design (controlled trials versus observational studies), provenance (developing versus developed countries), and timing of compared feeding groups (three to seven months versus later).

DATA COLLECTION AND ANALYSIS

: Two reviewers independently assessed study quality (using a priori assessment criteria) and extracted data.

MAIN RESULTS

: Twenty independent studies meeting the selection criteria were identified by the literature search: nine from developing countries (two of which were controlled trials in Honduras) and 11 from developed countries (all observational studies). The two trials did not receive high methodologic quality ratings but were nonetheless superior to any of the observational studies included in this review. The observational studies were of variable quality; in addition, their nonexperimental designs were not able to exclude potential sources of confounding and selection bias. Definitions of exclusive breastfeeding varied considerably across studies. Neither the trials nor the observational studies suggest that infants who continue to be exclusively breastfed for six months show deficits in weight or length gain, although larger sample sizes would be required to rule out modest differences in risk of undernutrition. The data are conflicting with respect to iron status, but at least in developing country settings where newborn iron stores may be suboptimal, suggest that exclusive breastfeeding without iron supplementation through six months may compromise hematologic status. Based primarily on an observational analysis of a large randomized trial in Belarus, infants who continue exclusive breastfeeding for six months or more appear to have a significantly reduced risk of one or more episodes of gastrointestinal infection. No significant reduction in risk of atopic eczema, asthma, or other atopic outcomes has been demonstrated in studies from Finland, Australia, and Belarus. Data from the two Honduran trials suggest that exclusive breastfeeding through six months is associated with delayed resumption of menses and more rapid postpartum weight loss in the mother.

REVIEWER'S CONCLUSIONS

: We found no objective evidence of a 'weanling's dilemma'. Infants who are exclusively breastfed for six months experience less morbidity from gastrointestinal infection than those who are mixed breastfed as of three or four months, and no deficits have been demonstrated in growth among infants from either developing or developed countries who are exclusively breastfed for six months or longer. Moreover, the mothers of such infants have more prolonged lactational amenorrhea. Although infants should still be managed individually so that insufficient growth or other adverse outcomes are not ignored and appropriate interventions are provided, the available evidence demonstrates no apparent risks in recommending, as a general policy, exclusive breastfeeding for the first six months of life in both developing and developed country settings. Large randomized trials are recommended in both types of setting to rule out small effects on growth and to confirm the reported health benefits of exclusive breastfeeding for six months or beyond.