Environmental factors in the etiology of esophageal atresia and congenital diaphragmatic hernia: Results of a case-control study

Role of genetics and the environment in the etiology of congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a congenital malformation characterized by failure of diaphragm closure during embryonic development, leading to pulmonary hypoplasia and pulmonary hypertension, which contribute significantly to morbidity and mortality. The occurrence of CDH and pulmonary hypoplasia is theorized to result from both abnormalities in signaling pathways of smooth muscle cells in pleuroperitoneal folds and mechanical compression by abdominal organs within the chest cavity on the developing lungs. Although, the precise etiology of diaphragm maldevelopment in CDH is not fully understood, it is believed that interplay between genes and the environment contributes to its onset. Approximately 30% of patients with CDH possess chromosomal or single gene defects and these patients tend to have inferior outcomes compared with those without genetic associations. At present, approximately 150 gene variants have been linked to the occurrence of CDH. The variable expression of the CDH phenotype in the presence of a recognized genetic predisposition can be explained by an environmental effect on gene penetrance and expression. The retinoic acid pathway is thought to play an essential role in the interactions of genes and environment in CDH. However, apart from the gradually maturing retinol hypothesis, there is limited evidence implicating other environmental factors in CDH occurrence. This review aims to describe the pathogenesis of CDH by summarizing the genetic defects and potential environmental influences on CDH development.

The etiology of congenital diaphragmatic hernia: the retinoid hypothesis 20 years later

Congenital diaphragmatic hernia (CDH) is a severe birth defect and a major cause of neonatal respiratory distress. Impacting ~2-3 in 10,000 births, CDH is associated with a high mortality rate, and long-term morbidity in survivors. Despite the significant impact of CDH, its etiology remains incompletely understood. In 2003, Greer et al. proposed the Retinoid Hypothesis, stating that the underlying cause of abnormal diaphragm development in CDH was related to altered retinoid signaling. In this review, we provide a comprehensive update to the Retinoid Hypothesis, discussing work published in support of this hypothesis from the past 20 years. This includes reviewing teratogenic and genetic models of CDH, lessons from the human genetics of CDH and epidemiological studies, as well as current gaps in the literature and important areas for future research. The Retinoid Hypothesis is one of the leading hypotheses to explain the etiology of CDH, as we continue to better understand the role of retinoid signaling in diaphragm development, we hope that this information can be used to improve CDH outcomes. IMPACT: This review provides a comprehensive update on the Retinoid Hypothesis, which links abnormal retinoic acid signaling to the etiology of congenital diaphragmatic hernia. The Retinoid Hypothesis was formulated in 2003. Twenty years later, we extensively review the literature in support of this hypothesis from both animal models and humans.

The role of genes and environment in the etiology of congenital diaphragmatic hernias

Structural birth defects are a common cause of abnormalities in newborns. While there are cases of structural birth defects arising due to monogenic defects or environmental exposures, many birth defects are likely caused by a complex interaction between genes and the environment. A structural birth defect with complex etiology is congenital diaphragmatic hernias (CDH), a common and often lethal disruption in diaphragm development. Mutations in more than 150 genes have been implicated in CDH pathogenesis. Although there is generally less evidence for a role for environmental factors in the etiology of CDH, deficiencies in maternal vitamin A and its derivative embryonic retinoic acid are strongly associated with CDH. However, the incomplete penetrance of CDH-implicated genes and environmental factors such as vitamin A deficiency suggest that interactions between genes and environment may be necessary to cause CDH. In this review, we examine the genetic and environmental factors implicated in diaphragm and CDH development. In addition, we evaluate the potential for gene-environment interactions in CDH etiology, focusing on the potential interactions between the CDH-implicated gene, Gata4, and maternal vitamin A deficiency.

Maternal cigarette smoking and alcohol consumption and congenital diaphragmatic hernia

Background

Congenital diaphragmatic hernia (CDH) occurs when abnormal diaphragm development allows herniation of abdominal organs into the thoracic cavity. Its etiopathogenesis is not well understood, but cigarette smoking and alcohol exposure may impact diaphragm development. Using data from a large, population‐based case–control study, we examined associations between maternal cigarette smoking and alcohol consumption and CDH in offspring.

Methods

We analyzed maternal interview reports of cigarette smoking and alcohol consumption during early pregnancy for 831 children with CDH and 11,416 children without birth defects with estimated dates of delivery during 1997–2011. Generalized linear mixed effects models with a random intercept for study site were used to estimate associations between measures of exposure to smoking (any, type, frequency, duration) and alcohol (any, quantity, frequency, variability, type) for all CDH combined and selected subtypes (Bochdalek and Morgagni).

Results

Mothers of 280 (34.0%) case and 3,451 (30.3%) control children reported early pregnancy exposure to cigarette smoking. Adjusted odds ratios for all CDH were increased for any (1.3; 95% confidence interval 1.1–1.5), active (1.3, 1.0–1.7), and passive (1.4, 1.1–1.7) smoking. Early pregnancy alcohol consumption was reported by mothers of 286 (34.9%) case and 4,200 (37.0%) control children; odds were near the null for any consumption (0.9, 0.8–1.1) and consumption with (0.9, 0.7, 1.1) or without (0.9, 0.8, 1.1) binging. Estimates for smoking and alcohol tended to be higher for Bochdalek CDH and Morgagni CDH than those for all CDH.

Conclusions

Findings suggest that maternal early pregnancy exposure to cigarette smoking, but less so to alcohol consumption, contributes to CDH. These findings need to be replicated in additional large studies that use systematic case ascertainment and classification, detailed exposure assessment, and examine subtype‐specific associations.

Parental risk factors for congenital diaphragmatic hernia - a large German case-control study

Background

Evidence for periconceptional or prenatal environmental risk factors for the development of congenital diaphragmatic hernia (CDH) is still scarce. Here, in a case-control study we investigated potential environmental risk factors in 199 CDH patients compared to 597 healthy control newborns.

Methods

The following data was collected: time of conception and birth, maternal BMI, parental risk factors such as smoking, alcohol or drug intake, use of hairspray, contact to animals and parental chronic diseases. CDH patients were born between 2001 and 2019, all healthy control newborns were born in 2011. Patients and control newborns were matched in the ratio of three to one.

Results

Presence of CDH was significantly associated with maternal periconceptional alcohol intake (odds ratio = 1.639, 95% confidence interval 1.101–2.440, p = 0.015) and maternal periconceptional use of hairspray (odds ratio = 2.072, 95% confidence interval 1.330–3.229, p = 0.001).

Conclusion

Our study suggests an association between CDH and periconceptional maternal alcohol intake and periconceptional maternal use of hairspray. Besides the identification of novel and confirmation of previously described parental risk factors, our study underlines the multifactorial background of isolated CDH.

Unraveling the Genetics of Congenital Diaphragmatic Hernia: An Ongoing Challenge

Congenital diaphragmatic hernia (CDH) is a congenital structural anomaly in which the diaphragm has not developed properly. It may occur either as an isolated anomaly or with additional anomalies. It is thought to be a multifactorial disease in which genetic factors could either substantially contribute to or directly result in the developmental defect. Patients with aneuploidies, pathogenic variants or de novo Copy Number Variations (CNVs) impacting specific genes and loci develop CDH typically in the form of a monogenetic syndrome. These patients often have other associated anatomical malformations. In patients without a known monogenetic syndrome, an increased genetic burden of de novo coding variants contributes to disease development. In early years, genetic evaluation was based on karyotyping and SNP-array. Today, genomes are commonly analyzed with next generation sequencing (NGS) based approaches. While more potential pathogenic variants are being detected, analysis of the data presents a bottleneck-largely due to the lack of full appreciation of the functional consequence and/or relevance of the detected variant. The exact heritability of CDH is still unknown. Damaging de novo alterations are associated with the more severe and complex phenotypes and worse clinical outcome. Phenotypic, genetic-and likely mechanistic-variability hampers individual patient diagnosis, short and long-term morbidity prediction and subsequent care strategies. Detailed phenotyping, clinical follow-up at regular intervals and detailed registries are needed to find associations between long-term morbidity, genetic alterations, and clinical parameters. Since CDH is a relatively rare disorder with only a few recurrent changes large cohorts of patients are needed to identify genetic associations. Retrospective whole genome sequencing of historical patient cohorts using will yield valuable data from which today's patients and parents will profit Trio whole genome sequencing has an excellent potential for future re-analysis and data-sharing increasing the chance to provide a genetic diagnosis and predict clinical prognosis. In this review, we explore the pitfalls and challenges in the analysis and interpretation of genetic information, present what is currently known and what still needs further study, and propose strategies to reap the benefits of genetic screening.

Prevalence and risk factors for congenital diaphragmatic hernia: A global view

PURPOSE

To determine the global prevalence for congenital diaphragmatic hernia (CDH) and identify CDH-related risk factors.

METHODS

Using a defined strategy, a systematic review of the literature was conducted according to PRISMA guidelines, searching for population-based epidemiological studies to evaluate the prevalence of CDH globally and per country. Studies containing overlapping populations or timeframes were excluded. CDH-related risk factors were calculated by meta-analysis using RevMan5.3 and expressed as risk ratio and 95% confidence interval.

RESULTS

Prevalence: Of 8230 abstracts screened, 30 full-text articles published between 1980 and 2019 were included. The overall prevalence of CDH was 2.3 in 10,000 births (16,710 CDH babies in 73,663,758 livebirths).

RISK FACTORS

From 9 studies we found that male sex [RR 1.38 (1.05-1.80), p=0.02] and maternal age >35 years [RR 1.69 (1.26-2.25), p=0.0004] were associated with CDH. Conversely, maternal black ethnicity resulted as a protective factor [RR 0.82 (0.77-0.89, p<0.00001].

CONCLUSION

This study reveals that there is a worldwide paucity of population-based studies, and those studies that report on prevalence and risk factors come from a small number of countries. The prevalence of CDH varies within and across geographical world regions. The main risk factors for CDH identified are male sex and older maternal age. More epidemiological studies, involving more world regions, are needed to identify possible strategies to help strengthen our understanding of the risk factors, provide clinicians with the tools necessary for prenatal and postnatal counseling, and inform policy makers on how to strategize CDH care in different parts of the world.

TYPE OF STUDY

Systematic review and meta-analysis.

LEVEL OF EVIDENCE

Level III.

Genetic Mouse Models and Induced Pluripotent Stem Cells for Studying Tracheal-Esophageal Separation and Esophageal Development

Esophagus and trachea arise from a common origin, the anterior foregut tube. The compartmentalization process of the foregut into the esophagus and trachea is still poorly understood. Esophageal atresia/tracheoesophageal fistula (EA/TEF) is one of the most common gastrointestinal congenital defects with an incidence rate of 1 in 2,500 births. EA/TEF is linked to the disruption of the compartmentalization process of the foregut tube. In EA/TEF patients, other organ anomalies and disorders have also been reported. Over the last two decades, animal models have shown the involvement of multiple signaling pathways and transcription factors in the development of the esophagus and trachea. Use of induced pluripotent stem cells (iPSCs) to understand organogenesis has been a valuable tool for mimicking gastrointestinal and respiratory organs. This review focuses on the signaling mechanisms involved in esophageal development and the use of iPSCs to model and understand it.

Infantile hypertrophic pyloric stenosis in patients with esophageal atresia

BACKGROUND

Patients born with esophageal atresia (EA) have a higher incidence of infantile hypertrophic pyloric stenosis (IHPS), suggestive of a relationship. A shared etiology makes sense from a developmental perspective as both affected structures are foregut derived. A genetic component has been described for both conditions as single entities and EA and IHPS are variable components in several monogenetic syndromes. We hypothesized that defects disturbing foregut morphogenesis are responsible for this combination of malformations.

METHODS

We investigated the genetic variation of 15 patients with both EA and IHPS with unaffected parents using exome sequencing and SNP array-based genotyping, and compared the results to mouse transcriptome data of the developing foregut.

RESULTS

We did not identify putatively deleterious de novo mutations or recessive variants. However, we detected rare inherited variants in EA or IHPS disease genes or in genes important in foregut morphogenesis, expressed at the proper developmental time-points. Two pathways were significantly enriched (p < 1 × 10^-5 ): proliferation and differentiation of smooth muscle cells and self-renewal of satellite cells.

CONCLUSIONS

None of our findings could fully explain the combination of abnormalities on its own, which makes complex inheritance the most plausible genetic explanation, most likely in combination with mechanical and/or environmental factors. As we did not find one defining monogenetic cause for the EA/IHPS phenotype, the impact of the corrective surgery could should be further investigated.

Patterns of malformation associated with esophageal atresia/tracheoesophageal fistula: A retrospective single center study

Esophageal atresia/tracheoesophageal fistula (EA/TEF) is one of the most common gastrointestinal birth defects. It can occur in isolation or in association with other birth defects or genetic syndromes. We retrospectively reviewed the EA/TEF cases evaluated at Rady Children's Hospital San Diego (San Diego, CA) between 2007 and 2016. Data were collected for 157 patients. The majority of patients (105, 66.8%) had an associated major malformation present, and 52 patients (33.1%) had isolated EA/TEF. The patients with associated malformations were distributed as follows: 16 patients (10.2%) had a known genetic syndrome (the most common being Trisomy 21 in 11 patients); six patients (3.8%) had a suspected genetic syndrome; one patient had a suspected teratogenic syndrome (diabetic embryopathy); 30 patients had VACTERL association (19.1%); 32 patients had a "partial VACTERL" association (only two VACTERL-type defects without other malformation); nine patients (5.7%) had one additional non-VACTERL-type birth defect, two patients had VACTERL-type defects plus auricular malformations; and nine patients (5.7%) were classified as "unknown syndrome." A classification of the patterns of malformation of patients with congenital EA/TEF is proposed based on reviewing the data of this relatively large and phenotypically diverse patient group.

Maternal Risk Factors and Perinatal Characteristics in Congenital Diaphragmatic Hernia: A Nationwide Population-Based Study

BACKGROUND

The etiology of congenital diaphragmatic hernia (CDH) remains poorly understood. We hypothesize that environmental factors play an important role in the development of CDH.

AIM

The objective of this study was to investigate associated maternal risk factors in pregnancies with CDH.

MATERIAL AND METHODS

The study was a nationwide, population-based prospective case-control study consisting of a cohort of newborn children entered into the records of pregnant women receiving antenatal care in Sweden, registered in the Medical Birth Registry during the period from January 1, 1982 to December 31, 2015. The study outcome CDH and the different exposures were assessed through linkage to the Swedish National Patient Registry for both cases and mothers.

RESULTS

A total of 972 cases of CDH were registered into one of the national registries in Sweden between 1982 and 2015. The incidence of neonates with CDH in Sweden from 1982 to 2015 was 3/10,000 live births. The mortality rate during the study period was 31%. Maternal age, ethnicity, parity, exposure to tobacco, BMI, IVF, previous history of spontaneous abortion or intrauterine fetal demise, and coexisting chronic diseases (urinary tract infection, chronic renal disease, pregestational diabetes, epilepsy, asthma, ulcerative colitis, inflammatory bowel disease, or systemic lupus erythematous) were not associated with an increased risk of CDH in the fetus. There was a significant association between maternal hypertension and the risk of the child being affected by CDH (OR 3.32, 95% CI 1.41-7.79, p = 0.01). No association was found between preeclampsia and CDH.

CONCLUSIONS

Pregestational hypertension is associated with an increased risk of giving birth to a baby with CDH, but no association was observed in pregnancies developing preeclampsia and the occurrence of CDH.

Trends, correlates, and survival of infants with congenital diaphragmatic hernia and its subtypes

OBJECTIVE

To identify the live-birth prevalence, trends, correlates, and neonatal and 1-year survival rates of congenital diaphragmatic hernia.

METHODS

Using a population-based, retrospective cohort study design, we examined 1,025 cases of congenital diaphragmatic hernia from the 1998-2012 Florida Birth Defects Registry. We used Poisson and joinpoint regression models to compute prevalence ratios and temporal trends, respectively. Kaplan-Meier survival curves and Cox proportional hazards regression were used to describe neonatal and 1-year survival and estimate hazard ratios representing the predictors of infant survival.

RESULTS

The birth prevalence of congenital diaphragmatic hernia was 3.19 per 10,000 live births (95% confidence interval [CI]: 3.00-3.39); there was a 4.2% yearly increase among multiple cases only. Among all cases, maternal education less than high school (prevalence ratio: 1.25, 95% CI: 1.02-1.53), high school/associate degree/GED (prevalence ratio: 1.15, 95% CI: 1.01-1.32), multiple birth (prevalence ratio: 1.38, 95% CI: 1.05-1.81), and male sex (prevalence ratio: 1.18, 95% CI: 1.05-1.32) were associated with increased risk for congenital diaphragmatic hernia. The 24-hr, neonatal, and 1-year survival rates were 93.6%, 79.8%, and 71.2%, respectively. The highest hazard ratio of 17.87 (95% CI: 1.49-213.82) was observed for neonatal mortality among cases associated with chromosomal anomalies and born <37 weeks at < 1,500 g. Among isolated cases, multiple birth (hazard ratio: 0.41, 95% CI: 0.20-0.86) was associated with decreased 1-year mortality.

CONCLUSION

Low maternal education and multiple birth may be linked to congenital diaphragmatic hernia. The trends in prevalence, epidemiologic correlates, and predictors of early survival can differ between congenital diaphragmatic hernia subtypes-isolated, multiple, and chromosomal.© 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Comparison of environmental risk factors for esophageal atresia, anorectal malformations, and the combined phenotype in 263 German families

Esophageal atresia with or without tracheoesophageal fistula (EA/TEF) and anorectal malformations (ARM) represent the severe ends of the fore- and hindgut malformation spectra. Previous research suggests that environmental factors are implicated in their etiology. These risk factors might indicate the influence of specific etiological mechanisms on distinct developmental processes (e.g. fore- vs. hindgut malformation). The present study compared environmental factors in patients with isolated EA/TEF, isolated ARM, and the combined phenotype during the periconceptional period and the first trimester of pregnancy in order to investigate the hypothesis that fore- and hindgut malformations involve differing environmental factors. Patients with isolated EA/TEF (n = 98), isolated ARM (n = 123), and the combined phenotype (n = 42) were included. Families were recruited within the context of two German multicenter studies of the genetic and environmental causes of EA/TEF (great consortium) and ARM (CURE-Net). Exposures of interest were ascertained using an epidemiological questionnaire. Chi-square, Fisher's exact, and Mann-Whitney U-tests were used to assess differences between the three phenotypes. Newborns with isolated EA/TEF and the combined phenotype had significantly lower birth weights than newborns with isolated ARM (P = 0.001 and P < 0.0001, respectively). Mothers of isolated EA/TEF consumed more alcohol periconceptional (80%) than mothers of isolated ARM or the combined phenotype (each 67%). Parental smoking (P = 0.003) and artificial reproductive techniques (P = 0.03) were associated with isolated ARM. Unexpectedly, maternal periconceptional multivitamin supplementation was most frequent among patients with the most severe form of disorder, i.e. the combined phenotype (19%). Significant differences in birth weight were apparent between the three phenotype groups. This might be attributable to the limited ability of EA/TEF fetuses to swallow amniotic fluid, thus depriving them of its nutritive properties. Furthermore, the present data suggest that fore- and hindgut malformations involve differing environmental factors. Maternal periconceptional multivitamin supplementation was highest among patients with the combined phenotype. This latter finding is contrary to expectation, and warrants further analysis in large prospective epidemiological studies.

Human exposure to environmental contaminants and congenital anomalies: a critical review

Congenital anomalies are an important cause of infant mortality and disability. Developmental exposure to environmental contaminants is thought to increase the risk for congenital anomalies. Herein, we describe a critical review of the literature conducted between February and March 2014 yielding 3057 references from which 97 unique relevant articles published from 2003 through 2014 were evaluated. Common congenital anomalies including hypospadias, cryptorchidism, anogenital distance (AGD), congenital heart defects and oral clefts were well represented in the literature whereas other outcomes such as neural tube defects, limb deficiency defects and gastroschisis were rarely described. While definitions used for congenital anomalies and methods of ascertainment were usually consistent across studies, inconsistencies were frequently found in grouping of different congenital heart defects. Despite strong links between some congenital anomalies and parental occupation, these studies are unable to provide clear insight into the specific chemicals responsible owing to lack of direct measures of exposure. In comparison, data are mixed for contaminant exposures at concentrations representative of results from contemporary biomonitoring studies. Of the environmental contaminants studied, the association between phthalate exposures and developmental abnormalities of the male reproductive tract received the greatest attention. Important limitations of the literature studied relate to adequacy of sample size, absence of or weaknesses in exposure assessment methodologies, failure to account for biological plausibility and grouping of congenital anomalies with divergent mechanisms. We conclude that the literature is inadequate at this time to support a conclusion that exposure to environmental contaminants are or are not associated with increased risks for congenital anomalies in the general population.

Environmental factors in the etiology of isolated and nonisolated esophageal atresia in a Chinese population: A case-control study

BACKGROUND

Esophageal atresia (EA) is a common birth defect that occurs with tracheoesophageal fistula (TEF), although etiological studies on EA/TEF have produced inconsistent results.

METHODS

The aim of this study was to examine the association between environmental factors during pregnancy and the risk of EA/TEF in a Chinese population. Cases of isolated EA and nonisolated EA and unaffected controls were identified between July 2005 and November 2015, and face-to-face questionnaires concerning exposure to environmental factors were administered to the birth mothers of 130 cases and 400 controls. The adjusted odds ratio (OR) and 95% confidence interval (CI) were calculated to assess the association between environmental factors and the risk of EA/TEF.

RESULTS

The results of this case-control study suggest that lower maternal education (p < 0.0001), maternal binge drinking (OR = 2.63; 95% CI, 1.05-6.6) and pickled food consumption (OR = 2.04; 95% CI, 1.31-3.71) during pregnancy increase the risk of EA in offspring, while maternal folic acid supplementation (OR = 0.45; 95% CI, 0.29-0.71) is significantly associated with a decreased risk of EA.

CONCLUSION

These results suggest a role for environmental exposures in the etiology of EA/TEF; however, further studies are needed to replicate the observed associations. Birth Defects Research (Part A) 106:840-846, 2016. © 2016 Wiley Periodicals, Inc.

Maternal smoking during pregnancy and birth defects in children: a systematic review with meta-analysis

This systematic review aimed to investigate the association between maternal smoking during pregnancy and birth defects in children. We performed an electronic search of observational studies in the databases ovid MEDLINE (1950 to April 2010), LILACS and SciELO. We included 188 studies with a total of 13,564,914 participants (192,655 cases). Significant positive associations were found between maternal smoking and birth defects in the following body systems: cardiovascular (OR: 1.11; 95%CI: 1.03-1.19), digestive (OR: 1.18; 95%CI: 1.07-1.30), musculoskeletal (OR: 1.27; 95%CI: 1.16-1.39) and face and neck (OR: 1.28; 95%CI: 1.19-1.37). The strength of association between maternal smoking and birth defects measured by the OR (95%CI) is significantly related to the amount of cigarettes smoked daily (χ2 = 12.1; df = 2; p = 0.002). In conclusion, maternal smoking during pregnancy is associated with congenital malformations in children and this association is dose-dependent.

Respiratory Care of Infants and Children with Congenital Tracheo-Oesophageal Fistula and Oesophageal Atresia

Despite acute respiratory and chronic respiratory and gastro-intestinal complications, most infants and children with a history of oesophageal atresia / trachea-oesophageal fistula [OA/TOF] can expect to live a fairly normal life. Close multidisciplinary medical and surgical follow-up can identify important co-morbidities whose treatment can improve symptoms and optimize pulmonary and nutritional outcomes. This article will discuss the aetiology, classification, diagnosis and treatment of congenital TOF, with an emphasis on post-surgical respiratory management, recognition of early and late onset complications, and long-term clinical outcomes.

[Diseases of the diaphragm]

The diaphragm is the main muscle involved in ventilation and is supplied exclusively by the phrenic nerves. Congenital defects of the diaphragm muscle or phrenic nerve injury cause diaphragmatic paralysis-eventration. Prognosis and treatment depend on whether involvement is unilateral or bilateral and on the patient's previous clinical status. In addition, the diaphragm is an anatomical barrier between the thoracic and abdominal cavities and is traversed by the esophagus and important vascular and nerve structures. Abnormal dilation of the natural orifices of the diaphragm or loss of its continuity can cause abdominal structures to pass into the chest cavity, an occurrence known as diaphragmatic hernias. According to their etiology, hernias are divided into congenital, acquired and traumatic. Clinical manifestations, prognosis and treatment depend mainly on hernia size and age at diagnosis. Like any muscle, the diaphragm can develop benign or malignant primary tumors. However, diaphragm involvement due to tumors arising in adjacent organs is much more common. The prognosis is good in benign primary tumors and poor in both primary and secondary malignant tumors. This article reviews the main anatomical and physiological characteristics of the diaphragm, routes of surgical access and the most frequent diseases affecting this structure.

Maternal medical and behavioral risk factors for congenital diaphragmatic hernia

PURPOSE

Maternal factors contributing to the etiology of congenital diaphragmatic hernia (CDH) remain unclear. We hypothesized that specific maternal medical conditions (pregestational diabetes, hypertension), and behaviors (alcohol, tobacco) would be associated with CDH.

METHODS

We conducted a population-based case-control study using Washington State birth certificates linked to hospital discharge records (1987-2009). We identified all infants with CDH (n=492). Controls were randomly selected among non-CDH infants. Maternal data were extracted from the birth record. Logistic regression was used to adjust for covariates.

RESULTS

Cases and controls were generally similar regarding demographics, although CDH infants were more likely to be male than controls (58.5% vs. 52.5%). Isolated and complex (multiple-anomaly) CDH had similar characteristics. Each of the exposures of interest was more common among case mothers than among control mothers. In univariate analysis, alcohol use, hypertension, and pregestational diabetes were each significantly associated with the outcome. After multivariate adjustment, only alcohol use (OR=3.65, p=0.01) and pregestational diabetes (OR=12.53, p=0.003) maintained significance. Results were similar for both isolated and complex CDH.

CONCLUSIONS

Maternal pregestational diabetes and alcohol use are significantly associated with occurrence of CDH in infants. These are important modifiable risk factors to consider with regard to efforts seeking to impact the incidence of CDH.

Dietary vitamin A intake below the recommended daily intake during pregnancy and the risk of congenital diaphragmatic hernia in the offspring

BACKGROUND

Vitamin A has been related to the etiology of congenital diaphragmatic hernia (CDH). We performed a case-control study to investigate whether maternal dietary vitamin A intake is related to CDH in the offspring.

METHODS

Thirty-one pregnancies diagnosed with CDH and 46 control pregnancies were included during the study. After CDH diagnosis and inclusion of controls by risk set sampling, maternal vitamin A intake was investigated with a food frequency questionnaire. Serum retinol and retinol-binding protein were determined. Univariable and multivariable logistic regression models were used to calculate risk estimates with adjustment for potential confounders.

RESULTS

We found no significant differences in the overall nutrient and vitamin A intake between case and control mothers. After stratification in body mass index (BMI) categories, case mothers with normal weight showed a lower energy adjusted vitamin A intake (685 vs. 843 μg retinol activity equivalents [RAEs] / day; p = 0.04) and a slightly lower serum retinol (1.58 vs. 1.67 μmol/L; p = 0.08) than control mothers. Vitamin A intake <800 μg retinol activity equivalents (recommended daily intake) in normal weight mothers was associated with a significantly increased CDH risk (odds ratio [OR], 7.2; 95% confidence interval [CI], 1.5-34.4; p = 0.01). Associations were not significantly different in underweight and overweight mothers.

CONCLUSIONS

In normal-weight mothers, dietary vitamin A intake during pregnancy below the recommended daily intake is significantly associated with an increased risk of a child with CDH. This finding supports the retinoid hypothesis in human CDH, but warrants further investigation in larger study populations. Birth Defects Research (Part A), 2013. © 2013 Wiley Periodicals, Inc.

Developmental and genetic aspects of congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a frequent occurring cause of neonatal respiratory distress and occurs 1 in every 3,000 liveborns. Ventilatory support and pharmaceutical treatment of the co-occurring lung hypoplasia and pulmonary hypertension are insufficient in, respectively, 20% of isolated cases and 60% of complex ones leading to early perinatal death. The exact cause of CDH remains to be identified in the majority of human CDH patients and prognostic factors predicting treatment refraction are largely unknown. Their identification is hampered by the multifactorial and heterogenic nature of this congenital anomaly. However, application of high-resolution molecular cytogenetic techniques to patients' DNA now enables detection of chromosomal aberrations in 30% of the patients. Furthermore, recent insights in rodent embryogenesis pointed to a specific disruption of the early mesenchymal structures in the primordial diaphragm of CDH-induced offspring. Together, these data allowed for the introduction of new hypotheses on CDH pathogenesis, although many issues remain to be resolved. In this review, we have combined these new insights and remaining questions on diaphragm pathogenesis with a concise overview of the clinical, embryological, and genetic data available.

Eosinophilic esophagitis after esophageal atresia: is there an association? Case presentation and literature review

Eosinophilic esophagitis (EoE) is a relatively new condition resulting in dysphagia or symptoms resembling gastroesophageal reflux disease, symptoms that also are common in patients with a history of esophageal atresia. We present 2 patients with persistent dysphagia after repair of esophageal atresia that was caused by EoE. Although the exact etiology and pathogenesis of EoE remain unclear, it is now generally accepted that it is the result of a T-helper cell 2-type immune response with a crucial role for the eosinophil-specific chemotaxis factor eotaxin 3 and eosinophils. Because there are genetic similarities between esophageal atresia and EoE, we speculate that patients with esophageal atresia are at increased risk for developing EoE.

Maternal smoking in pregnancy and birth defects: a systematic review based on 173 687 malformed cases and 11.7 million controls

BACKGROUND

There is uncertainty over whether maternal smoking is associated with birth defects. We conducted the first ever comprehensive systematic review to establish which specific malformations are associated with smoking.

METHODS

Observational studies published 1959–2010 were identified (Medline), and included if they reported the odds ratio (OR) for having a non-chromosomal birth defect among women who smoked during pregnancy compared with non-smokers. ORs adjusted for potential confounders were extracted (e.g. maternal age and alcohol), otherwise unadjusted estimates were used. One hundred and seventy-two articles were used in the meta-analyses: a total of 173 687 malformed cases and 11 674 332 unaffected controls.

RESULTS

Significant positive associations with maternal smoking were found for: cardiovascular/heart defects [OR 1.09, 95% confidence interval (CI) 1.02–1.17]; musculoskeletal defects (OR 1.16, 95% CI 1.05–1.27); limb reduction defects (OR 1.26, 95% CI 1.15–1.39); missing/extra digits (OR 1.18, 95% CI 0.99–1.41); clubfoot (OR 1.28, 95% CI 1.10–1.47); craniosynostosis (OR 1.33, 95% CI 1.03–1.73); facial defects (OR 1.19, 95% CI 1.06–1.35); eye defects (OR 1.25, 95% CI 1.11–1.40); orofacial clefts (OR 1.28, 95% CI 1.20–1.36); gastrointestinal defects (OR 1.27, 95% CI 1.18–1.36); gastroschisis (OR 1.50, 95% CI 1.28–1.76); anal atresia (OR 1.20, 95% CI 1.06–1.36); hernia (OR 1.40, 95% CI 1.23–1.59); and undescended testes (OR 1.13, 95% CI 1.02–1.25). There was a reduced risk for hypospadias (OR 0.90, 95% CI 0.85–0.95) and skin defects (OR 0.82, 0.75–0.89). For all defects combined the OR was 1.01 (0.96–1.07), due to including defects with a reduced risk and those with no association (including chromosomal defects).

CONCLUSIONS

Birth defects that are positively associated with maternal smoking should now be included in public health educational materials to encourage more women to quit before or during pregnancy.

Etiology of esophageal atresia and tracheoesophageal fistula: "mind the gap"

Esophageal atresia and tracheoesophageal fistula (EA/TEF) are major congenital malformations affecting 1:3500 live births. Current research efforts are focused on understanding the etiology of these defects. We describe well-known animal models, human syndromes, and associations involving EA/TEF, indicating its etiologically heterogeneous nature. Recent advances in genotyping technology and in knowledge of human genetic variation will improve clinical counseling on etiologic factors. This review provides a clinical summary of environmental and genetic factors involved in EA/TEF.

Chronic hypertension with related drug treatment of pregnant women and congenital abnormalities in their offspring: a population-based study

Chronic hypertension (CH) is a common chronic disease and occurs frequently in pregnant women. The teratogenic/fetotoxic effect of certain antihypertensive drugs has been shown. The objective of this study was to investigate the association between pregnant women with CH and the possible risk of congenital abnormalities (CAs) among their offspring. The prevalence of medically recorded CH in the prenatal maternity logbook was compared between 1030 pregnant women who later had offspring with CA (case group) and 1579 pregnant women with CH who later delivered newborn infants without CA (control group). Control newborn infants were matched to cases in the population-based data set of the Hungarian Case-Control Surveillance System of Congenital Abnormalities during 1980-1996. Of 23 different CA groups with informative offspring, esophageal atresia/stenosis was a greater risk in pregnant women with CH (adjusted odds ratios with 95% confidence intervals: 3.1, 1.4-6.8). In conclusion, a higher risk of esophageal atresia/stenosis was found in the offspring of pregnant women with severe CH, which could not be explained by related drug treatments. This finding requires confirmation or lack thereof by future studies.

Maternal periconceptional exposure to cigarette smoking and alcohol consumption and congenital diaphragmatic hernia

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a major birth defect that occurs when abdominal organs herniate through a diaphragmatic opening into the thoracic cavity and is associated with high mortality (>50%). The etiology of CDH is not well understood.

METHODS

Using data from the National Birth Defects Prevention Study, we examined associations between CDH and maternal periconceptional exposure (1 month before through the third month of pregnancy) to cigarette smoking and alcohol. Interview reports of exposures were provided by mothers of CDH (n = 503) and unaffected control (n = 6703) infants delivered from October 1997 through December 2005. Any exposure (yes/no), as well as quantity (average number of cigarettes or drinks), type (active/passive smoking; beer, wine, distilled spirits), and duration (e.g., number of months exposed) were examined. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were calculated for all CDH cases combined, selected subtypes (Bochdalek, Morgagni, not otherwise specified), and phenotypes (infants with/without additional major birth defects).

RESULTS

The aOR for any smoking was nonsignificantly elevated for all CDH cases combined. Odds of any smoking was significant for isolated Bochdalek CDH (aOR, 1.9; 95% CI, 1.2-3.0). The aORs associated with all measures of alcohol consumption were near unity for each CDH category examined. Stratification of smoking exposure by alcohol consumption and stratification of alcohol consumption by smoking exposure did not appreciably change the aORs.

CONCLUSIONS

These findings identified periconceptional smoking exposure as a potential risk factor for CDH. Future studies need to confirm our findings and explore possible pathways accounting for the teratogenic effect of smoking.

Maternal periconceptional exposure to cigarette smoking and alcohol and esophageal atresia +/- tracheo-esophageal fistula

BACKGROUND

Esophageal atresia (EA) is a moderately frequent birth defect that often occurs with tracheo-esophageal fistula (TEF). Etiologic studies for EA+/-TEF have produced inconsistent results.

METHODS

This study used data from the National Birth Defects Prevention Study (NBDPS) to examine the association between maternal periconceptional exposure to cigarette smoking and alcohol and EA+/-TEF. Cases of EA+/-TEF and unaffected controls with an estimated date of delivery from October 1997 through December 2003 were identified, and telephone interview reports for smoking and alcohol exposure were obtained from birth mothers of 334 cases and 4,967 controls. Odds ratios (OR)s and 95% confidence intervals (CI)s, adjusted for several covariates, were calculated to assess associations.

RESULTS

ORs were near unity for all EA+/-TEF cases combined and any periconceptional exposure to cigarette smoking (OR = 1.1; CI = 0.8,1.6) or alcohol (OR = 1.2; CI = 0.8,1.8). For cigarette smoking, some elevated ORs were found but varied by type of smoking exposure. No consistent patterns were identified for number of cigarettes smoked per day. For alcohol, ORs were weak to moderately elevated with increasing number of drinks consumed and for binge drinkers compared to non-binge drinkers. ORs were further elevated among mothers who reported active+passive exposure to cigarette smoking and alcohol (OR = 2.5; CI = 1.1,5.6). For both exposures, ORs were higher for cases with additional major defects compared to isolated cases.

CONCLUSIONS

These results, based on one of the largest published samples of EA+/-TEF cases, suggest a role for these exposures in the etiology of EA+/-TEF, although further study is needed to replicate the observed associations.