Changing lifestyles and oral clefts occurrence in Denmark

Gene×environment associations in orofacial clefting

This chapter reviews the evidence of gene×environment interactions (G×E) in the etiology of orofacial cleft birth defects (OFCs), specifically cleft lip (CL), cleft palate (CP), and cleft lip with or without cleft palate (CL/P). We summarize the current state of our understanding of the genetic architecture of nonsyndromic OFCs and the evidence that maternal exposures during pregnancy influence risk of OFCs. Further, we present possible candidate gene pathways for these exposures including metabolism of folates, metabolism of retinoids, retinoic acid receptor signaling, aryl hydrocarbon receptor signaling, glucocorticoid receptor signaling, and biotransformation and transport. We review genes in these pathways with prior evidence of association with OFCs, genes with evidence from prior candidate gene G×E studies, and genes identified from genome-wide searches specifically for identifying G×E. Finally, we suggest future directions for G×E research in OFCs.

Higher maternal age is associated with higher occurrence of cleft lip/palate in neonates under intensive care

Aim: To assess the prevalence of cleft lip and/or cleft palate (CL/P) and associated variables in neonates admitted to neonatal intensive care units (ICU). Methods: Medical charts for neonates born and admitted to the ICU between 2012 and 2018 were reviewed. Obstetric and neonatal variables were collected by a trained researcher. In the case group, all neonates with CL/P were included. The control group was formed by matching sex, prematurity and month of birth using random number generation. Neonates with congenital malformations were excluded from the control group. Adjusted logistic regression was used (p<0.05). Results: The prevalence of CL/P was 0.43% (n=15). Five cases were excluded, as pairing was not possible. Twenty neonates were included in the control group. In the final multivariate model, CL/P was only associated with increased maternal age. For each year of increase in maternal age, neonates had a 35.2% higher chance of presenting CL/P (95% confidence interval: 1.021–1.792). Conclusions: Higher maternal age was associated with higher occurrence of CL/P in neonates admitted to the ICU. No other neonatal or maternal independent variables were associated with CL/P. Due to missing data, interpretation of study results must be approached with caution.

The impact of changing cigarette smoking habits and smoke-free legislation on orofacial cleft incidence in the United Kingdom: Evidence from two time-series studies

BACKGROUND

Both active and passive cigarette smoking have previously been associated with orofacial cleft aetiology. We aimed to analyse the impact of declining active smoking prevalence and the implementation of smoke-free legislation on the incidence of children born with a cleft lip and/or palate within the United Kingdom.

METHODS AND FINDINGS

We conducted regression analysis using national administrative data in the United Kingdom between 2000-2018. The main outcome measure was orofacial cleft incidence, reported annually for England, Wales and Northern Ireland and separately for Scotland. First, we conducted an ecological study with longitudinal time-series analysis using smoking prevalence data for females over 16 years of age. Second, we used a natural experiment design with interrupted time-series analysis to assess the impact of smoke-free legislation. Over the study period, the annual incidence of orofacial cleft per 10,000 live births ranged from 14.2-16.2 in England, Wales and Northern Ireland and 13.4-18.8 in Scotland. The proportion of active smokers amongst females in the United Kingdom declined by 37% during the study period. Adjusted regression analysis did not show a correlation between the proportion of active smokers and orofacial cleft incidence in either dataset, although we were unable to exclude a modest effect of the magnitude seen in individual-level observational studies. The data in England, Wales and Northern Ireland suggested an 8% reduction in orofacial cleft incidence (RR 0.92, 95%CI 0.85 to 0.99; P = 0.024) following the implementation of smoke-free legislation. In Scotland, there was weak evidence for an increase in orofacial cleft incidence following smoke-free legislation (RR 1.16, 95%CI 0.94 to 1.44; P = 0.173).

CONCLUSIONS

These two ecological studies offer a novel insight into the influence of smoking in orofacial cleft aetiology, adding to the evidence base from individual-level studies. Our results suggest that smoke-free legislation may have reduced orofacial cleft incidence in England, Wales and Northern Ireland.

Epidemiology of orofacial clefts in a Danish county over 35 years - Before and after implementation of a prenatal screening programme for congenital anomalies

In 2004 the Danish National Board of Health changed its screening recommendations. Since 2005 a first trimester screening for Down syndrome and a prenatal ultrasound screening for congenital anomalies in the second trimester of pregnancy has been offered to all pregnant women. The aim of this study was to describe the prevalence of cleft lip with or without cleft palate and cleft palate in a Danish area and to describe associated anomalies and the development in prenatal diagnosis over time. The study was based on data from the EUROCAT Registry for Funen County. The registry is based on multiple data sources and includes information about live births, fetal deaths with a gestational age >20 weeks and terminations of pregnancy after prenatal diagnosis of severe fetal anomaly. The study included all fetuses/infants out of a population of 182,907 births diagnosed with orofacial clefts born between 1980 and 2014. There were 271 cases diagnosed with cleft lip with or without cleft palate and 127 cases diagnosed with cleft palate, giving a prevalence of 14.8 per 10,000 births for cleft lip with or without cleft palate and 6.9 per 10,000 births for cleft palate. There were no significant changes in prevalence over time for the two anomalies, calculated with and without inclusion of genetic and chromosomal cases. Overall 66 cases were diagnosed prenatally (17% of total). For isolated cleft lip with or without cleft palate none of the 157 cases born before 2005 were diagnosed prenatally compared to 34 of 58 cases (59%) born in 2005-2014 (p < 0.01). The proportion of liveborn infants with multiple congenital anomalies also changed after 2005 with 15% (39/266) of all liveborn infants with orofacial clefts born 1980-2004 having multiple anomalies compared to 7% (7/96) in 2005-2014 (p < 0.05). The implementation of the new screening programme in 2005 has given a major change in prenatal detection rate and reduced the proportion of liveborn infants with orofacial clefts classified as multiple congenital anomaly cases. The prevalence of cleft lip with or without cleft palate was higher than reported from many other countries.

Parental age in relation to the severity of cleft lip and/or palate

OBJECTIVE

To investigate parental age in relation to the severity of cleft diagnosis in a population-based consecutive sample of individuals with clefts.

SETTING/SAMPLE

Retrospective, consecutive.

MATERIAL/METHODS

The sample comprised 545 consecutive cases with nonsyndromic clefts (437 individuals with cleft lip with/without cleft palate [CL ± P] and 106 individuals with isolated cleft palate [CP]) and parental ages recorded. The groups were subdivided according to the extent/severity of cleft. Unilateral clefts were divided according to left/right sidedness. Logistic regression was used to analyse the association between parental age and risk of severe cleft separately for CL ± P and CP, as well as between parental age and risk of right-sided cleft.

RESULTS

In CL ± P, the risk of a complete cleft in the offspring increases with maternal age when the paternal age exceeds approximately 29 years. Moreover, the risk is higher when both parents are old than when both parents are young. In CP, no statistically significant results were identified. However, there were clear trends that indicated a similar pattern as that for CL ± P. No association was identified between increased parental age and the sidedness of clefts.

CONCLUSIONS

Parental age seems to contribute to cleft severity, as older parents showed a higher risk of having offspring with a complete cleft than younger parents.

Nucleotide variants of the NAT2 and EGF61 genes in patients in Northern China with nonsyndromic cleft lip with or without cleft palate

BACKGROUND

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is a common orofacial congenital anomaly. The objective of the present study was to analyze the association of single nucleotide polymorphisms (SNPs) in the NAT2 and EGF61genes with NSCL/P in a Chinese population.

METHODS

The frequencies of NAT2 (rs1799929)and EGF61 (rs4444903) gene variations were examined in a group of 285 NSCL/P patients and in 315 controls. Peripheral venous blood samples were collected for DNA extraction. Genotyping of the 2 SNPs was carried out using a mini sequencing (SNaPshot) method. Data were analyzed using the chi-square test.

RESULTS

We found a significant association between the EGF61 (rs4444903) and NSCL/P (P = .01) genes.Conversely, NAT2 (rs1799929) was not significantly different between the cases and the control group.The genotype frequencies of rs4444903GA showed a significant difference compared with GG genotype as a reference (odds ratio = 0.59; 95% confidence interval: 0.42-0.84, P = .01).

CONCLUSION

Our study showed that the EGF61 rs4444903GA genotype had a decreased risk of NSCL/P. Our data provides further evidence regarding the role of EGF61 variations in the development of NSCL/P in families of the studied populations.

Use of Psychotropic Medications and Visits to Psychiatrists and Psychologists among Individuals with Nonsyndromic Oral Clefts: A Population-Based Cohort Study

BACKGROUND

Oral clefts (OCs) are among the most common congenital malformations and can have a large impact on the life of the affected individual. Research findings regarding the psychological and psychosocial consequences of OC are inconclusive.

METHODS

Using Danish nationwide registers, we investigated redeemed prescriptions of psychotropic medication during 1996 to 2012 and visits to psychiatrists and psychologists during 1996 to 2011 among individuals born with nonsyndromic OC in Denmark between 1936 and 2009 and a comparison cohort of individuals without OC. This includes 8244 individuals with OC and 82,665 individuals without OC.

RESULTS

The Cox regression analysis revealed 12% (95% confidence interval [CI], 7 to 16%) increased risk of using any psychotropic medication for individuals with OC. When examining by cleft type, higher risks for medication use were observed in individuals with cleft lip and palate (CLP) or cleft palate (CP) only. The largest increased relative risk was found for use of antipsychotics and stimulants for individuals with CP followed by use of antipsychotics for individuals with CLP. We found increased risk of visits to psychiatrists for individuals with CP and no increased risk for visits to psychologists for either group.

CONCLUSIONS

This study indicates that a small group of individuals with nonsyndromic OC, in particular those with palatal involvement, have greater risk of using psychotropic medications. However, elevated use was also observed among younger individuals with cleft lip (CL) only. There seems to be only a modest increase in visits to health professionals for psychological reasons. Undiagnosed syndromes (e.g., 22q11 deletion syndrome), may, however, contribute to an overestimation of the associations. Birth Defects Research 109:824-835, 2017. © 2017 Wiley Periodicals, Inc.

Psychiatric Diagnoses in Individuals with Non-Syndromic Oral Clefts: A Danish Population-Based Cohort Study

Background

The aim of this study was to investigate the risk of psychiatric diagnoses in individuals with non-syndromic oral clefts (OC) compared with individuals without OC, including ages from 1 to 76 years.

Methods

Linking four Danish nationwide registers, we investigated the risk of psychiatric diagnoses at Danish psychiatric hospitals during the period 1969–2012 for individuals born with non-syndromic OC in Denmark 1936–2009 compared with a cohort of 10 individuals without OC per individual with OC, matched by sex and birth year. The sample included 8,568 individuals with OC, observed for 247,821 person-years, and 85,653 individuals without OC followed for 2,501,129 person-years.

Results

A total of 953 (11.1%) of the individuals with OC (9.6% for cleft lip (CL), 10.8% for cleft lip and palate (CLP) and 13.1% for cleft palate (CP)) and 8,117 (9.5%) in the comparison group had at least one psychiatric diagnosis. Cox proportional hazard regression model revealed that individuals with OC had significantly higher risk of a psychiatric diagnosis (hazard ratio (HR) = 1.19, 95% CI: 1.12–1.28). When examining cleft type, no difference was found for CL (HR = 1.03, 95% CI: 0.90–1.17), but CLP was associated with a small increased risk (HR = 1.13, 95% CI: 1.01–1.26), whereas individuals with CP had the largest increased risk (HR = 1.45, 95% CI: 1.30–1.62). The largest differences were found in schizophrenia-like disorders, mental retardation and pervasive developmental disorders, but we found no increased risk of mood disorders and anxiety-related disorders.

Conclusion

Individuals with non-syndromic OC had significantly higher risk of psychiatric diagnoses compared with individuals without OC. However, the elevated risk was observed for individuals with CLP and CP but not for individuals with CL and the absolute risk increase was modest.

Cholesteatoma risk in 8,593 orofacial cleft cases and 6,989 siblings: A nationwide study

OBJECTIVES/HYPOTHESIS

To estimate the risk of surgically treated middle ear cholesteatoma in individuals with a nonsyndromic orofacial cleft and in their siblings compared with the general population.

STUDY DESIGN

Historical cohort study.

METHODS

Using the unique civil registration number for linkage, data from three national registers were used for the Danish 1936-2009 birth cohorts. Hazard ratios (HRs) were estimated with Cox regression analyses using age as the underlying time variable. Individuals were followed from January 1, 1977 until time of surgically treated cholesteatoma, and censored at emigration, death, or end of follow-up (December 31, 2010).

RESULTS

A total of 8,593 individuals with nonsyndromic orofacial cleft and 6,989 siblings were identified, undergoing 201 and 21 first-time cholesteatoma surgeries, respectively. A 5% random sample of the Danish population comprising 249,708 persons without an orofacial cleft was created, and 175,724 siblings to these persons were identified. These controls underwent 485 and 332 first-time cholesteatoma surgeries, respectively. For individuals with cleft lip and palate the HR for cholesteatoma surgery was 14 (95% confidence interval [CI], 12-18) and for individuals with cleft palate the HR was 20 (95% CI, 16-24) when compared with the random sample. In siblings of individuals with cleft palate, the HR for cholesteatoma surgery was 2.1 (95% CI, 1.1-4.1) when compared with siblings of the random sample.

CONCLUSIONS

A 20-fold increase in the risk of cholesteatoma was found in individuals with cleft palate, whereas cleft lip did not pose a risk of cholesteatoma. Furthermore, the study indicates an increased risk of cholesteatoma in unaffected siblings of individuals with cleft palate.

LEVEL OF EVIDENCE

2b Laryngoscope, 125:1225-1229, 2015.

Ethnic Variation in Oral Cleft Occurrence in Denmark 1981–2002

Objective

To examine differences in oral cleft (OC) occurrence based on maternal only and parental country of origin in Denmark from 1981 to 2002.

Methods

Data on all live births from the Danish Medical Birth Register from 1981 to 2002 were linked with the Danish Facial Cleft Database. Cleft cases were categorized into isolated and nonisolated cleft lip with or without palate (CL/P) and cleft palate only (CP). Birth prevalence was calculated as cases per 1,000 live born children by maternal country of origin, world region, and mixed parental groups.

Results

We identified 3094 OC cases among 1,319,426 live births. Danish-born women had an OC birth prevalence of 2.38 with a 95% confidence interval (CI) (2.29–2.47) and foreign-born women a significant lower prevalence of 2.01 (CI, 1.77–2.27). This difference was explained by a lower isolated CL/P birth prevalence among foreign-born women of 0.97 (CI, 0.81–1.16) versus 1.35 (CI, 1.28–1.41). No significant differences were seen for the remaining subtypes. Parents with the same foreign country of origin had a lower overall OC (1.63; CI, 1.35–1.94) and isolated CL/P (0.76; CI, 0.57–0.99) birth prevalence than Danish-born parents. This was not the case for any of the mixed parental groups. Overall and subtype prevalence rates varied according to maternal categories of world region.

Conclusion

In this study we found differences in OC occurrence among all live births in the Danish population based on maternal country of origin from 1981 to 2002. Danish-born women had higher OC and isolated CL/P birth prevalence compared with foreign-born women.

Genetics of cleft lip and cleft palate

Orofacial clefts are common birth defects and can occur as isolated, nonsyndromic events or as part of Mendelian syndromes. There is substantial phenotypic diversity in individuals with these birth defects and their family members: from subclinical phenotypes to associated syndromic features that is mirrored by the many genes that contribute to the etiology of these disorders. Identification of these genes and loci has been the result of decades of research using multiple genetic approaches. Significant progress has been made recently due to advances in sequencing and genotyping technologies, primarily through the use of whole exome sequencing and genome-wide association studies. Future progress will hinge on identifying functional variants, investigation of pathway and other interactions, and inclusion of phenotypic and ethnic diversity in studies.

[Orofacial closure defects: cleft lip and palate. A literature review]

Orofacial clefts are a common problem that can lead to significant healthcare use and costs, as well as suffering on the part of the affected individuals and families. There are several theories explaining their origin, but some of the findings are inconsistent. The most accepted theories involve a major genetic basis that could be modified by the presence of external agents. Understanding the underlying causes could help to prevent its occurrence, an area in which the family physician can play an important role.

Prevention of oro-facial clefts in developing world

Oro-facial cleft (OFC) remains a prominent health issue in developed and developing countries alike. It is the commonest craniofacial birth defect in humans. Mounting evidence suggest a polygenic, multifactorial and a list of epigenetic events. Primary prevention of OFC is based on recognition of the etiologic and risk factors. While a number of preventive strategies are in place for OFC in most developed countries of the world, the majority of developing countries are distant from achieving this goal for a number of reasons. Notable among these are a huge knowledge and practice gap in the field of genetics and dearth of accurate data. In addition, improper coordination and absenteeism from antenatal care contributed greatly to this set back. With ongoing efforts aimed at determining the genetics of nonsyndromic OFC in developing countries, researches directed at identifying environmental factors should equally be in place. Pending the outcome of these, implicated environmental and attitudinal risk factors in other populations could serve as preventive template in health education and interventions. Since risk factors vary between populations, definitive and effective preventive strategies and models would vary from place to place and from time to time. Frantic effort directed at identifying specific implicated risk factors in developing countries should include developing and keeping comprehensive national perinatal database and centralization of antenatal care protocol. Additionally, active health education at every level and a focus on developing manpower in the field of genetics should be in place. These would be designed and tailored toward identified, proven, and emerging risk factors.

X-linked genes and risk of orofacial clefts: evidence from two population-based studies in Scandinavia

BACKGROUND

Orofacial clefts are common birth defects of complex etiology, with an excess of males among babies with cleft lip and palate, and an excess of females among those with cleft palate only. Although genes on the X chromosome have been implicated in clefting, there has been no association analysis of X-linked markers.

METHODOLOGY/PRINCIPAL FINDINGS

We added new functionalities in the HAPLIN statistical software to enable association analysis of X-linked markers and an exploration of various causal scenarios relevant to orofacial clefts. Genotypes for 48 SNPs in 18 candidate genes on the X chromosome were analyzed in two population-based samples from Scandinavia (562 Norwegian and 235 Danish case-parent triads). For haplotype analysis, we used a sliding-window approach and assessed isolated cleft lip with or without cleft palate (iCL/P) separately from isolated cleft palate only (iCPO). We tested three statistical models in HAPLIN, allowing for: i) the same relative risk in males and females, ii) sex-specific relative risks, and iii) X-inactivation in females. We found weak but consistent associations with the oral-facial-digital syndrome 1 (OFD1) gene (formerly known as CXORF5) in the Danish iCL/P samples across all models, but not in the Norwegian iCL/P samples. In sex-specific analyses, the association with OFD1 was in male cases only. No analyses showed associations with iCPO in either the Norwegian or the Danish sample.

CONCLUSIONS

The association of OFD1 with iCL/P is plausible given the biological relevance of this gene. However, the lack of replication in the Norwegian samples highlights the need to verify these preliminary findings in other large datasets. More generally, the novel analytic methods presented here are widely applicable to investigations of the role of X-linked genes in complex traits.

Risk of breast cancer in families with cleft lip and palate

PURPOSE

To test whether female subjects in families with cleft lip and/or palate (CL/P) have an increased risk of breast cancer.

METHODS

By using the Danish Facial Cleft Registry, we identified female subjects with CL/P, mothers of children with CL/P, and sisters to CL/P cases for the Danish birth cohorts 1911-1975. These subjects were compared with a 5% random sample of these cohorts regarding the incidence and age of onset for breast cancer registered in the Danish Hospital Discharge Register 1977-2005.

RESULTS

Examining 48,404 person-years for 1809 female CL/P cases (49 breast cancer cases) and 212,795 person-years for 7935 female relatives (188 breast cancer cases), we found no increased breast cancer risk for either CL/P cases (hazard ratio [HR], 1.23; 95% confidence interval (CI), 0.92-1.63), mothers of children with CL/P (HR, 0.93; 95% CI, 0.80-1.08), or sisters of CL/P cases (HR, 0.94; 95% CI, 0.55-1.60), nor was there any significant differences in age of onset.

CONCLUSION

Both epidemiological and genetic studies have suggested common etiological factors for breast cancer and CL/P. However, in this population-based study we were not able to confirm a general increase in the risk of breast cancer among female subjects in families with CL/P.

Risk of oral clefts in twins

BACKGROUND

Small studies have indicated that twinning increases the risk of oral cleft.

METHODS

We used data from a Danish national population-based cohort study to investigate whether twinning was associated with isolated oral cleft, and to estimate the twin probandwise concordance rate and heritability. Twins (207 affected/130,710) and singletons (7766 affected/4,798,526) born from 1936 through 2004 in Denmark were ascertained by linkage among the Danish Facial Cleft Database, the Danish Twin Registry, and the Civil Registration System. We computed oral cleft prevalence and prevalence proportion ratio for twins versus singletons, stratified for 3 subphenotypes. Probandwise concordance rates and heritability for twins were estimated for 2 phenotypes--cleft lip with or without cleft palate (CL/P) and cleft palate (CP).

RESULTS

The prevalence of oral cleft was 15.8 per 10,000 twins and 16.6 per 10,000 singletons (prevalence proportion ratio = 0.95; 95% confidence interval = 0.83-1.1). This prevalence was similar for monozygotic and dizygotic twins. The probandwise concordance rate was higher for CL/P for monozygotic twins than for dizygotic twins (50% vs. 8%, respectively). A similar contrast was present for CP. Recurrence risk for both types of clefts was greater in dizygotic twins than in non-twin siblings. Heritability estimates were above 90% for both CL/P and CP.

CONCLUSIONS

No excess risk of oral cleft could be demonstrated for twins compared with singletons. The concordance rates and heritability estimates for both types of clefts show a strong genetic component.

Cleft lip and palate: understanding genetic and environmental influences

Clefts of the lip and/or palate (CLP) are common birth defects of complex aetiology. CLP can occur in isolation or as part of a broad range of chromosomal, Mendelian or teratogenic syndromes. Although there has been marked progress in identifying genetic and environmental triggers for syndromic CLP, the aetiology of the more common non-syndromic (isolated) forms remains poorly characterized. Recently, using a combination of epidemiology, careful phenotyping, genome-wide association studies and analysis of animal models, several distinct genetic and environmental risk factors have been identified and confirmed for non-syndromic CLP. These findings have advanced our understanding of developmental biology and created new opportunities for clinical translational research.

Fetal genetic risk of isolated cleft lip only versus isolated cleft lip and palate: a subphenotype analysis using two population-based studies of orofacial clefts in Scandinavia

Background

Cleft lip only (CLO) and cleft lip and palate (CLP) are commonly regarded as variants of the same defect and traditionally combined to form the single group of cleft lip with or without cleft palate (CL/P) prior to analysis. However, recent data have suggested that at least a subgroup of isolated CLO may be etiologically distinct from isolated CLP.

Methods

To explore fetal genetic risk of isolated CLO separately from isolated CLP, we performed a sub-phenotype analysis using two population-based studies of clefts in Scandinavia. One hundred and twenty-one isolated CLO, 190 isolated CLP, and 592 control triads were available from Norway(1996–2001), and a further 76 isolated CLO and 107 isolated CLP triads were available from Denmark (1991–2001). Genotypes for 1315 SNPs in 334 autosomal cleft candidate genes were analyzed using two complementary statistical methods, TRIMM and HAPLIN, to look for genetic associations across the two national samples.

Results

Both TRIMM and HAPLIN identified strong associations between FGF12 and isolated CLO in both populations. In addition, only TRIMM identified associations with IRF6 and VCL , and only HAPLIN found an association with CX43 . When analyses were repeated on the larger sample of isolated CLP, no significant associations were found with FGF12 , IRF6, VCL or CX43 .

Conclusions

Despite some inconsistency in the pattern of associations across the two populations, the associations themselves were phenotype-specific. While both IRF6 and FGF12 have previously shown strong associations with isolated CL/P, the associations with VCL and CX43 are novel and warrant further investigation in other isolated CLO samples.

Recurrence risk for offspring of twins discordant for oral cleft: a population-based cohort study of the Danish 1936-2004 cleft twin cohort

Our objective in this Danish population-based cohort study was to estimate the recurrence risk of isolated oral cleft (OC) for offspring of the unaffected co-twins of OC discordant twin pairs and to compare this risk to the recurrence risk in the offspring of the affected co-twin as well as to the risk in the background population. During 1936-2004, 207 twin pairs were ascertained, among whom at least one twin had an OC. The index persons were twins discordant for OC who had children (N=117), and their offspring (N=239). The participants were ascertained by linkage between The Danish Facial Cleft Database, The Danish Twin Registry and The Danish Civil Registration System. In the study OC recurrence risk for offspring of the affected and unaffected twin and relative risk were compared to the background prevalence. We found that among 110 children of the 54 OC affected twins, two (1.8%) children had OC corresponding to a significantly increased relative risk (RR=10; 95% CI 1.2-35) when compared to the frequency in the background population. Among the 129 children of the 63 unaffected twins, three (2.3%) children were affected, corresponding to a significantly increased relative risk (RR=13; 95% CI 2.6-36) when compared the background prevalence. We concluded that in OC discordant twin pairs similar increased recurrence risks were found among offspring of both OC affected and OC unaffected twins. This provides further evidence for a genetic component in cleft etiology and is useful information for genetic counseling of twin pairs discordant for clefting.

Reproductive patterns among Danish women with oral clefts

OBJECTIVE

The aim of this study was to compare reproduction patterns among Danish women born with isolated oral clefts versus the Danish background population.

DESIGN AND SETTING

A nationwide population-based historic cohort study based on three registers: The Danish Facial Cleft Register, The Danish Civil Registration System, and the Fertility of Women and Couples Dataset.

PARTICIPANTS

Through linkages of the registers, the number of children and the exact age at childbirth of all Danish women born with an oral cleft from 1950 through 1988 (N = 1931) were obtained. These data were compared with similar data for the entire Danish female background population (N = 1,184,390).

RESULTS AND CONCLUSIONS

This study suggests that childlessness is higher among women born with an oral cleft (55%) than among women in the Danish background population (44%). Excluding women without children, women born with oral cleft had an average of 1.98 children per woman. This did not differ significantly from the background population (2.02 children/woman). Furthermore, the present study found that Danish women born with oral clefts on average were older (27.3 years of age) than the background population (24.7 years of age) when they had their first child (difference = 2.6 years, confidence interval = 2.41 to 2.80).

CONCLUSION

Danish women born with an oral cleft more often are childless or have their first child later, but if they have children, they tend to have as many children as other Danish women. Social, psychological, and biological reasons might be responsible for the reduced fertility.

Maternal genes and facial clefts in offspring: a comprehensive search for genetic associations in two population-based cleft studies from Scandinavia

BACKGROUND

Fetal conditions can in principle be affected by the mother's genotype working through the prenatal environment.

METHODOLOGY/PRINCIPAL FINDINGS

Genotypes for 1536 SNPs in 357 cleft candidate genes were available from a previous analysis in which we focused on fetal gene effects. After data-cleaning, genotypes for 1315 SNPs in 334 autosomal genes were available for the current analysis of maternal gene effects. Two complementary statistical methods, TRIMM and HAPLIN, were used to detect multi-marker effects in population-based samples from Norway (562 case-parent and 592 control-parent triads) and Denmark (235 case-parent triads). We analyzed isolated cleft lip with or without cleft palate (iCL/P) and isolated cleft palate only (iCP) separately and assessed replication by looking for genes detected in both populations by both methods. In iCL/P, neither TRIMM nor HAPLIN detected more genes than expected by chance alone; furthermore, the selected genes were not replicated across the two methods. In iCP, however, FLNB was identified by both methods in both populations. Although HIC1 and ZNF189 did not fully satisfy our stringency criterion for replication, they were strongly associated with iCP in TRIMM analyses of the Norwegian triads.

CONCLUSION/SIGNIFICANCE

Except for FLNB, HIC1 and ZNF189, maternal genes did not appear to influence the risk of clefting in our data. This is consistent with recent epidemiological findings showing no apparent difference between mother-to-offspring and father-to-offspring recurrence of clefts in these two populations. It is likely that fetal genes make the major genetic contribution to clefting risk in these populations, but we cannot rule out the possibility that maternal genes can affect risk through interactions with specific teratogens or fetal genes.

Autoantibodies to folate receptor alpha during early pregnancy and risk of oral clefts in Denmark

The objective of this study was to determine whether IgG and IgM autoantibodies to folate receptor alpha (FRalpha) in pregnant women are associated with an increased risk of oral cleft-affected offspring. A case-control study nested in the prospective Danish National Birth Cohort (100,418 pregnancies, enrolled during 1997-2003) was done. Hundred eighty-five children were born with an oral cleft. Maternal serum from their mothers (cases) was compared with maternal serum from 779 randomly selected mothers of nonmalformed children (controls). We found that the average level of FRalpha IgG autoantibodies did not differ significantly among cases and controls (p = 0.71). Slightly higher levels of FRalpha IgM autoantibodies were found among controls compared with cases. This was, however, not statistically significant (p = 0.06), except for mothers of children with isolated cleft lip (p = 0.04). Blocking of folate binding to FR was similar among cases and controls (p = 0.54). The results did not change when stratifying into the cleft subgroups, nor when only isolated oral cleft cases were considered. In conclusion, high maternal autoantibody levels and blocking of folate binding to FRalpha in maternal serum during pregnancy are not associated with an increased risk of oral clefts in the offspring in this population-based cohort.

A cohort study of recurrence patterns among more than 54,000 relatives of oral cleft cases in Denmark: support for the multifactorial threshold model of inheritance

OBJECTIVES

To determine if the anatomical severity of oral clefting affects familial recurrence in a large population based sample. To provide reliable recurrence risk estimates for oral cleft for first, second, and third degree relatives.

DESIGN

Population based cohort study.

SETTING

Denmark.

PARTICIPANTS

6776 individuals affected with an oral cleft born from 1952 to 2005 and 54 229 relatives.

MAIN OUTCOME MEASURES

Recurrence risk estimates for oral cleft for first, second, and third degree relatives and stratification by severity, specificity, parent of origin effect, and family size for first degree relatives.

RESULTS

For cleft lip and palate probands we observed recurrence risks for first, second, and third degree relatives of respectively 3.5% (95% CI 3.1% to 4.0%), 0.8% (95% CI 0.6% to 1.0%), and 0.6% (95% CI 0.4% to 0.8%). Individuals affected by the most severe oral cleft had a significantly higher recurrence risk among both offspring and siblings, eg, the recurrence risk for siblings of a proband with isolated bilateral cleft lip with cleft palate was 4.6% (95% CI 3.2 to 6.1) versus 2.5% (95% CI 1.8 to 3.2) for a proband born with a unilateral defect.

CONCLUSIONS

Anatomical severity does have an effect on recurrence in first degree relatives and the type of cleft is predictive of the recurrence type. Highly reliable estimates of recurrence have been provided for first cousins in addition to more accurate estimates for first and second degree relatives. These results and the majority of prior data continue to support a multifactorial threshold model of inheritance.

Genetic determinants of facial clefting: analysis of 357 candidate genes using two national cleft studies from Scandinavia

Background

Facial clefts are common birth defects with a strong genetic component. To identify fetal genetic risk factors for clefting, 1536 SNPs in 357 candidate genes were genotyped in two population-based samples from Scandinavia (Norway: 562 case-parent and 592 control-parent triads; Denmark: 235 case-parent triads).

Methodology/Principal Findings

We used two complementary statistical methods, TRIMM and HAPLIN, to look for associations across these two national samples. TRIMM tests for association in each gene by using multi-SNP genotypes from case-parent triads directly without the need to infer haplotypes. HAPLIN on the other hand estimates the full haplotype distribution over a set of SNPs and estimates relative risks associated with each haplotype. For isolated cleft lip with or without cleft palate (I-CL/P), TRIMM and HAPLIN both identified significant associations with IRF6 and ADH1C in both populations, but only HAPLIN found an association with FGF12. For isolated cleft palate (I-CP), TRIMM found associations with ALX3, MKX, and PDGFC in both populations, but only the association with PDGFC was identified by HAPLIN. In addition, HAPLIN identified an association with ETV5 that was not detected by TRIMM.

Conclusion/Significance

Strong associations with seven genes were replicated in the Scandinavian samples and our approach effectively replicated the strongest previously known association in clefting—with IRF6. Based on two national cleft cohorts of similar ancestry, two robust statistical methods and a large panel of SNPs in the most promising cleft candidate genes to date, this study identified a previously unknown association with clefting for ADH1C and provides additional candidates and analytic approaches to advance the field.

Identification of microdeletions in candidate genes for cleft lip and/or palate

BACKGROUND

Genome-wide association studies are now used routinely to identify genes implicated in complex traits. The panels used for such analyses can detect single nucleotide polymorphisms and copy number variants, both of which may help to identify small deleted regions of the genome that may contribute to a particular disease.

METHODS

We performed a candidate gene analysis involving 1,221 SNPs in 333 candidate genes for orofacial clefting, using 2,823 samples from 725 two- and three-generation families with a proband having cleft lip with or without cleft palate. We used SNP genotyping, DNA sequencing, high-resolution DNA microarray analysis, and long-range PCR to confirm and characterize the deletion events.

RESULTS

This dataset had a high duplicate reproducibility rate (99.98%), high Mendelian consistency rate (99.93%), and low missing data rate (0.55%), which provided a powerful opportunity for deletion detection. Apparent Mendelian inconsistencies between parents and children suggested deletion events in 15 individuals in 11 genomic regions. We confirmed deletions involving CYP1B1, FGF10, SP8, SUMO1, TBX1, TFAP2A, and UGT7A1, including both de novo and familial cases. Deletions of SUMO1, TBX1, and TFAP2A are likely to be etiologic.

CONCLUSIONS

These deletions suggest the potential roles of genes or regulatory elements contained within deleted regions in the etiology of clefting. Our analysis took advantage of genotypes from a candidate-gene-based SNP survey and proved to be an efficient analytical approach to interrogate genes potentially involved in clefting. This can serve as a model to find genes playing a role in complex traits in general.

Review on genetic variants and maternal smoking in the etiology of oral clefts and other birth defects

A spectrum of adverse pregnancy outcomes, including preterm birth, low birth weight, and birth defects has been linked with maternal smoking during pregnancy. This article includes a review of studies investigating interactions between genetic variants and maternal smoking in contributing to birth defects using oral clefting as a model birth defect. The primary gene-smoking studies for other major birth defects are also summarized. Gene-environment interaction studies for birth defects are still at an early stage with several mixed results, but evolving research findings have begun to document clinically and developmentally important interactions. As samples and data become increasingly available, more effort is needed in designing innovative analytical methods to study gene-environment interactions.

Folic acid supplements and risk of facial clefts: national population based case-control study

OBJECTIVE

To explore the role of folic acid supplements, dietary folates, and multivitamins in the prevention of facial clefts.

DESIGN

National population based case-control study.

SETTING

Infants born 1996-2001 in Norway.

PARTICIPANTS

377 infants with cleft lip with or without cleft palate; 196 infants with cleft palate alone; 763 controls.

MAIN OUTCOME MEASURES

Association of facial clefts with maternal intake of folic acid supplements, multivitamins, and folates in diet.

RESULTS

Folic acid supplementation during early pregnancy (> or =400 microg/day) was associated with a reduced risk of isolated cleft lip with or without cleft palate after adjustment for multivitamins, smoking, and other potential confounding factors (adjusted odds ratio 0.61, 95% confidence interval 0.39 to 0.96). Independent of supplements, diets rich in fruits, vegetables, and other high folate containing foods reduced the risk somewhat (adjusted odds ratio 0.75, 0.50 to 1.11). The lowest risk of cleft lip was among women with folate rich diets who also took folic acid supplements and multivitamins (0.36, 0.17 to 0.77). Folic acid provided no protection against cleft palate alone (1.07, 0.56 to 2.03).

CONCLUSIONS

Folic acid supplements during early pregnancy seem to reduce the risk of isolated cleft lip (with or without cleft palate) by about a third. Other vitamins and dietary factors may provide additional benefit.

Oral clefts and life style factors — A case-cohort study based on prospective Danish data

This study examines the association between oral clefts and first trimester maternal lifestyle factors based on prospective data from the Danish National Birth Cohort. The cohort includes approximately 100,000 pregnancies. In total 192 mothers gave birth to child with an oral cleft during 1997-2003. Information on risk factors such as smoking, alcohol consumption, tea, coffee, cola, and food supplements was obtained during pregnancy for these and 828 randomly selected controls. We found that first trimester maternal smoking was associated with an increased risk of oral clefts (odds ratio (OR): 1.50; 95% confidence interval (CIs): 1.05, 2.14). Although not statistically significant, we also saw associations with first trimester consumption of alcohol (OR: 1.11; CIs: 0.79, 1.55), tea (OR: 1.31; CIs: 0.93, 1.86), and drinking more than 1 l of cola per week (OR: 1.40; CIs: 0.92, 2.12). Furthermore supplementation with > or =400 mcg folic acid daily during the entire first trimester (OR: 0.75; CIs: 0.46, 1.22) suggested an inverse associated with oral clefts, similar to our results on coffee drinking. No effects were found for smaller doses of folic acid, vitamin A, B6 or B12 in this study. The present study found an association between oral clefts and smoking and, although not conclusive, supports an association of oral cleft with alcohol.

Cancer risk in persons with oral cleft--a population-based study of 8,093 cases

The authors conducted a nationwide study of the occurrence of cancer among 8,093 Danish oral cleft cases born in 1936 through 1998 and followed in the Danish Cancer Registry from 1968 through 1998, a total of 175,863 person-years, to assess a possible association between cancer and oral clefts. Observed and expected numbers of cancers among oral cleft cases were summarized as the overall and as 52 site-specific standardized incidence ratios. The expected overall number of all cancers was 131, but 140 incident cancers were found, corresponding to a standardized incidence ratio of 1.07 (95% confidence interval (CI): 0.90, 1.26). Analyses of the 52 sites for all oral cleft cases and analyses stratified for three cleft subgroups and the two sexes revealed only a few significant associations: an increased occurrence of breast cancer among females born with cleft lip and/or cleft palate (standardized incidence ratio (SIR) = 1.52, 95% CI: 1.05, 2.14), primary brain cancer among females born with cleft palate (SIR = 3.11, 95% CI: 1.14, 6.78), and primary lung cancer among males born with both cleft lip and cleft palate (SIR = 2.49, 95% CI: 1.00, 5.14). The results do not provide evidence for an increased overall cancer risk for individuals born with oral clefts.