Parental Birthplace Research Articles

From Multiracial Subjects to Multicultural Citizens: Social Stratification and Ethnic and Racial Classification among Children of Immigrants in the United Kingdom

This study examines how immigrant parents’ geographic origins correspond to their adult children's ethnic and racial self-classification; whether discrepancies are associated with socioeconomic status; and the implications of these patterns for assessing socioeconomic inequality. Using linked British census data, we identify immigrants’ children in 1971 and examine how they ethnically/racially self-classify in 2001. We find that fluidity in classification varies across groups, but higher educational attainment is consistently associated with less white British classification. Therefore, grouping immigrants’ children by ethnic/racial self-classification underestimates socioeconomic disadvantage for these groups. However, grouping by parental birthplace overlooks variation in racialization and disadvantage among children of immigrants from the same country of origin.

The Association of Infant Growth Patterns with Adiposity in Adolescence: Prospective Observations from Hong Kong's 'Children of 1997' Birth Cohort.

The role of infant growth in adiposity remains unclear. We used multivariable linear regression, with inverse probability weighting and multiple imputation to account for loss to follow-up, in a population-representative Chinese birth cohort, 'Children of 1997' in Hong Kong, to examine, in terms births, the adjusted association of infant (birth to 12 months) weight growth trajectories with body mass index (BMI) (n = 6861, 88% follow-up), waist-to-height ratio (WHtR), and waist-to-hip ratio (WHR) (n = 5398, 69% follow-up) at ∼ 14 years. Infant weight growth trajectories had graded associations with adolescent BMI and WHtR but not with WHR, such that compared with adolescents born light with slow infant growth, adolescents born heavy with fast infant growth had higher BMI z-score [0.60, 95% confidence interval (CI) 0.49, 0.70], higher WHtR z-score (0.17, 95% CI 0.08, 0.26) but similar WHR z-score (-0.02, 95% CI -0.11, 0.08), adjusted for sex, gestational age, parental education, parental BMI, parental height, and parental place of birth. Varying associations of infant growth with different adiposity measures suggest a complex role of infant growth in long-term health, perhaps because infant growth, or its underlying drivers, influences build and body composition as well as adiposity.

Epidemiology of early-onset Parkinson's disease in Finland.

The contribution of genetic causes to Parkinson's disease (PD) is strongest in early-onset cases. We ascertained a nationwide cohort of patients in order to study the genetic epidemiology of early-onset PD (EOPD) in Finland. By means of a search in a national database we ascertained all patients with EOPD. These patients had become eligible for reimbursement of PD drugs between the years 1995-2006 and were <55 years of age at the time of PD diagnosis. A total of 441 patients consented and provided clinical and genealogical information. The incidence of EOPD increased 1.7-fold between the years 1995-2006, the mean annual incidence being 3.3/100,000. Fifty-two patients (11.8%) reported an affected first-degree relative. The birthplaces of patients with PD among first-degree relatives were clustered in certain regions in the southwestern and western coastal provinces of Finland and in the eastern province of Savo. Furthermore, the distance between the birthplaces of the patients' parents was smaller for patients, who had first-degree relatives with PD than for patients with no family history of PD. Our data suggest that the incidence of EOPD is increasing. The birthplaces of patients with PD among first-degree relatives were clustered in certain provinces of Finland suggesting that monogenic forms of PD or genetic susceptibility of PD are present in the population.

Educational attainment influences levels of homozygosity through migration and assortative mating.

Individuals with a higher education are more likely to migrate, increasing the chance of meeting a spouse with a different ancestral background. In this context, the presence of strong educational assortment can result in greater ancestry differences within more educated spouse pairs, while less educated individuals are more likely to mate with someone with whom they share more ancestry. We examined the association between educational attainment and F roh (= the proportion of the genome consisting of runs of homozygosity [ROHs]) in ~2,000 subjects of Dutch ancestry. The subjects’ own educational attainment showed a nominally significant negative association with F roh (p = .045), while the contribution of parental education to offspring F roh was highly significant (father: p < 10-5; mother: p = 9×10-5), with more educated parents having offspring with fewer ROHs. This association was significantly and fully mediated by the physical distance between parental birthplaces (paternal education: p mediation = 2.4 × 10-4; maternal education: p mediation = 2.3 × 10-4), which itself was also significantly associated with F roh (p = 9 × 10-5). Ancestry-informative principal components from the offspring showed a significantly decreasing association with geography as parental education increased, consistent with the significantly higher migration rates among more educated parents. Parental education also showed a high spouse correlation (Spearman’s ρ = .66, p = 3 × 10-262). We show that less educated parents are less likely to mate with the more mobile parents with a higher education, creating systematic differences in homozygosity due to ancestry differences not directly captured by ancestry-informative principal components (PCs). Understanding how behaviors influence the genomic structure of a population is highly valuable for studies on the genetic etiology of behavioral, cognitive, and social traits.

Sociodemographic and hispanic acculturation factors and isolated anotia/microtia.

It has been observed in several studies that infants with anotia/microtia are more common among Hispanics compared with other racial/ethnic groups. We examined the association between selected Hispanic ethnicity and acculturation factors and anotia/microtia in the National Birth Defects Prevention Study. We examined data from mothers of 351 infants with isolated anotia/microtia and 8435 unaffected infants from the National Birth Defects Prevention Study with an expected delivery date from 1997 to 2007. Sociodemographic, maternal, and acculturation factors (e.g., age, maternal education, household income, body mass index, gestational diabetes, folic acid, smoking, alcohol intake, study center, parental birthplace, and years lived in the United States, maternal language) were assessed as overall risk factors and also as risk factors among subgroups of Hispanics (United States- and foreign-born) versus non-Hispanic whites. Compared with non-Hispanic whites, both United States- and foreign-born Hispanic mothers demonstrated substantially higher odds of delivering infants with anotia/microtia across nearly all strata of sociodemographic and other maternal factors (adjusted odds ratios range: 2.1-11.9). The odds of anotia/microtia was particularly elevated among Hispanic mothers who emigrated from Mexico after age five (adjusted odds ratios = 4.88; 95% confidence interval = 2.93-8.11) or who conducted the interview in Spanish (adjusted odds ratios = 4.97; 95% confidence interval = 3.00-8.24). We observed that certain sociodemographic and acculturation factors are associated with higher risks of anotia/microtia among offspring of Hispanic mothers.

Explaining Ethnic Inequality in the German Labor Market: Labor Market Institutions, Context of Reception, and Boundaries

The descendants of immigrants comprise nearly a third of the West German population under the age of 25 years and will soon become a substantial proportion of the native born labor force. Owing to the young age of this group, and a lack of governmental data on parental place of birth, there is currently little research that compares the labor market outcomes of the second generation of different origins. Exploiting the first data set to allow the disaggregation of all immigrant groups in Germany, this article draws on the concepts of context of reception and boundary crossing to explain variation in the labor market performance of different immigrant origin groups. Positively received ethnic Germans consistently perform better than negatively received guest worker origin groups. Labor market inequality is greatest among men and in obtaining employment. Ethnic differences are more compressed among women and for occupational attainment among the employed. The boundary crossing mechanisms of naturalization and intermarriage have modest association with labor market success. Findings suggest that successful integration in Germany is influenced by labor market institutions, which encourage inequality in unemployment while diminishing inequality amongst the employed.

Language Spoken at Home and Parental Birthplace Moderate the Association of Race/Ethnicity and Distorted Weight Perception

Distorted weight perception (DWP), specifically overestimating weight status, is common in adolescents and may lead to eating disorders. The authors examined the role of acculturation proxies as effect modifiers of the relationship between race/ethnicity and DWP in a diverse adolescent population. Analysis of the 2005 California Health Interview Survey showed that of 2955 adolescents with underweight or healthy weight status, 10.6% reported DWP. Latino adolescents had increased odds of DWP compared with white adolescents (adjusted odds ratio [aOR] = 3.02; 95% confidence interval [CI] = 2.00, 4.57). Latinos who spoke English and other language(s) at home (aOR = 3.38; 95% CI = 2.11, 5.41) and Latino (aOR = 5.00; 95% CI = 2.34, 10.72) and Asian (aOR = 3.10, 95% CI = 1.15, 8.35) adolescents who spoke no English at home had increased odds of DWP compared with white, English-only speakers. Latino adolescents had increased odds (aOR = 3.98, 95% CI = 2.45, 6.47) of DWP if neither parent was US born. Assessing acculturation proxies may help identify adolescents at risk of DWP.

Fine-scale estimation of location of birth from genome-wide single-nucleotide polymorphism data.

Systematic nonrandom mating in populations results in genetic stratification and is predominantly caused by geographic separation, providing the opportunity to infer individuals' birthplace from genetic data. Such inference has been demonstrated for individuals' country of birth, but here we use data from the Northern Finland Birth Cohort 1966 (NFBC1966) to investigate the characteristics of genetic structure within a population and subsequently develop a method for inferring location to a finer scale. Principal component analysis (PCA) shows that while the first PCs are particularly informative for location, there is also location information in the higher-order PCs, but it cannot be captured by a linear model. We introduce a new method, pcLOCATE, which is able to exploit this information to improve the accuracy of location inference. pcLOCATE uses individuals' PC values to estimate the probability of birth in each town and then averages over all towns to give an estimated longitude and latitude of birth using a fully Bayesian model. We apply pcLOCATE to the NFBC1966 data to estimate parental birthplace, testing with successively more PCs and finding the model with the top 23 PCs most accurate, with a median distance of 23 km between the estimated and the true location. pcLOCATE predicts the most recent residence of NFBC1966 individuals to a median distance of 47 km. We also apply pcLOCATE to Indian individuals from the London Life Sciences Prospective Population Study (LOLIPOP) data, and find that birthplace is predicated to a median distance of 54 km from the true location. A method with such accuracy is potentially valuable in population genetics and forensics.

Isolation by distance between spouses and its effect on children's growth in height

Heterosis is thought to be an important contributor to human growth and development. Marital distance (distance between parental birthplaces) is commonly considered as a factor favoring the occurrence of heterosis and can be used as a proximate measure of its level. The aim of this study is to assess the net effect of expected heterosis resulting from marital migration on the height of offspring, controlling for midparental height and socioeconomic status (SES). Height measurements on 2,675 boys and 2,603 girls ages 6 to 18 years from Ostrowiec Świętokrzyski, Poland were analyzed along with sociodemographic data from their parents. Midparental height was calculated as the average of the reported heights of the parents. Analyses revealed that marital distance, midparental height, and SES had a significant effect on height in boys and girls. The net effect of marital distance was much more marked in boys than girls, whereas other factors showed comparable effects. Marital distance appears to be an independent and important factor influencing the height of offspring. According to the "isolation by distance" hypothesis, greater distance between parental birthplaces may increase heterozygosity, potentially promoting heterosis. We propose that these conditions may result in reduced metabolic costs of growth among the heterozygous individuals.

Immigration Statistics for the Twenty-First Century

Of the three main contributors to population growth-fertility, mortality, and net migration-the latter is by far the most difficult to capture statistically. This article discusses the main sources of federal statistical data on immigration, each with its own characteristic set of strengths, weaknesses, possibilities, and limitations in the context of the interested social scientist. Among the key limitations, the article argues, are the elimination of parental birthplace from the Census and the lack of complete data concerning the legal statuses of the U.S. population. This article will conclude with suggestions on remedying such deficiencies, at relatively low marginal cost, such as the inclusion of questions on parental birthplace, instituting a regular survey of randomly selected legal immigrants, and the use of the "two-card method" in statistical data.

Testicular Germ Cell Cancer Incidence in an Immigration Perspective, Denmark, 1978 to 2003

The incidence rate of testicular germ cell cancer in Denmark increased up to the 1990s to become among the highest in the world. Since recently rate stabilization was suggested, we determined whether it is due to an increasing number of immigrants at lower risk for this cancer. The immigration status of more than 3.6 million men registered in the Danish Central Population Register between 1978 and 2003 was defined by birthplace (first generation immigrant) or parental birthplace (second generation immigrant). Linkage with the Danish Cancer Registry yielded 6,478 testicular cancer cases. Differences between populations are shown as SIR with the 95% CI. The testicular germ cell cancer incidence rate in first generation immigrants was lower than in native born Danish men (SIR 0.4, 95% CI 0.4-0.5). The rate in second generation immigrants was similar (SIR 0.9, 95% CI 0.7-1.1). The impact of immigrant status on the incidence rate increased with time from 0.6% in 1978 to 8.2% in 2003. Recent incidence rates in all men and only in men born in Denmark suggest stabilization. Our finding of a higher incidence rate in second generation immigrants than in their immigrant fathers confirms the early life programming of environmental factors in the etiology of testicular cancer. Our study also shows that trend analysis of the incidence rate of this cancer should consider immigration due to considerable country specific differences in morbidity.

Genome-wide Association Study in a High-Risk Isolate for Multiple Sclerosis Reveals Associated Variants in STAT3 Gene

Genetic risk for multiple sclerosis (MS) is thought to involve both common and rare risk alleles. Recent GWAS and subsequent meta-analysis have established the critical role of the HLA locus and identified new common variants associated to MS. These variants have small odds ratios (ORs) and explain only a fraction of the genetic risk. To expose potentially rare, high-impact alleles, we conducted a GWAS of 68 distantly related cases and 136 controls from a high-risk internal isolate of Finland with increased prevalence and familial occurrence of MS. The top 27 loci with p < 10(-4) were tested in 711 cases and 1029 controls from Finland, and the top two findings were validated in 3859 cases and 9110 controls from more heterogeneous populations. SNP (rs744166) within the STAT3 gene was associated to MS (p = 2.75 x 10(-10), OR 0.87, confidence interval 0.83-0.91). The protective haplotype for MS in STAT3 is a risk allele for Crohn disease, implying that STAT3 represents a shared risk locus for at least two autoimmune diseases. This study also demonstrates the potential of special isolated populations in search for variants contributing to complex traits.

Prevalence and Risk Factors for Adult Paternity Among Adolescent Females Ages 14 through 16 Years

To investigate sociodemographic factors associated with adolescent females ages 14-16 years having children fathered by males age 20 years or older and identify differences in correlates across rural, urban, and border areas. The method section was a cross-sectional study using Texas birth record data. From 2000 through 2004, there were 29,186 births to adolescent females aged 14-16 years with valid paternal age. Prevalence of and adjusted odds of paternal age of 20 years or older were identified by paternal and maternal factors. The Results section Having both parents born outside of the U.S. was associated with a 5.29 (95% CI: 4.82, 5.80) times increase in the odds of paternal age of 20 years or older as compared to having both parents born in the U.S. Parental place of birth was associated with greater odds of paternal age of 20 years or older in urban areas compared to rural or border areas. Compared to those with average or high educational attainment relative to age, low educational attainment relative to age was associated with an increase in the odds of paternal age of 20 years or older. This association was present whether maternal or paternal educational attainment was low relative to age. Messages are needed to help adolescent females avoid pregnancy with adult males. In addressing this specific prevention challenge, it is important to consider maternal/paternal place of birth and its association with adolescent births with adult males.

W1812 Rheumatologists Awareness and General Practice in Screening for Hepatitis B Virus (HBV) Infection Prior to Initiating Immunomodulating Therapies

Chronic hepatitis B infection affects approximately 400 million people worldwide, with a disproportionately high prevalence in Asian Pacific Islanders (APIs). HCC is the second leading cause of cancer deaths among APIA men. It is estimated that one in ten APIs is chronically infected with HBV. The guidelines set forth by various organizations lack consistency with regard to HBV screening in APIs. Although screening of all APIs for chronic HBV has been advocated by multiple research groups and mandated by recent legislation in Congress, the Center for Disease Control and Prevention and AASLD each recommend slightly different guidelines. As part of the San Francisco Hep B Free campaign, we offered free serologic screening and vaccination, if appropriate, to over 2000 APIs between January and October 2008. Of the total number of participants screened (2,118), 72 (3.4%) were chronically infected. Of those people who reported previous vaccination, 90 (32.5%) lacked protective antibodies and 3 (1.1%) were actually chronically infected. Among the APIs screened, 64 (3.3%) were chronically infected with HBV. Of those not chronically infected, 993 (51%) lacked protective antibodies and were at risk for future infections. Men were 1.5 times as likely as women to be chronically infected. Adults aged sixty or older were three times more likely to be infected than people under the age of sixty. APIs born in endemic regions were 4.6 times more likely to be chronically infected than U.S.-born APIs. In an earlier study by Hutton et al., a Markov model of different screening strategies suggested that it is cost-effective to screen all APIs, irrespective of birthplace. To date, no studies have examined the rates of chronic infection in secondand third-generation APIs, i.e. U.S.-born APIs whose parents were born in Asia or the U.S. Based on an interim analysis of the San Francisco Hep B Free Campaign, we hypothesize that it is not cost-effective to screen all APIs given the lower prevalence rates in 2nd and 3rd generation U.S.-born APIs. We plan to integrate the data from our screening program with Hutton's model to re-evaluate costeffectiveness of HBV screening across different generations of APIs. Clearly, there is a need for identification of hepatitis B cases in the API community and vaccination when appropriate. By identifying non-traditional risk factors such as parental birthplace in U.S.-born APIs, we hope to make screening efforts more targeted, cost-effective, and successful.

W1815 Elevated ALT Levels Are Common in Chinese Americans Without Hepatitis B

Chronic hepatitis B infection affects approximately 400 million people worldwide, with a disproportionately high prevalence in Asian Pacific Islanders (APIs). HCC is the second leading cause of cancer deaths among APIA men. It is estimated that one in ten APIs is chronically infected with HBV. The guidelines set forth by various organizations lack consistency with regard to HBV screening in APIs. Although screening of all APIs for chronic HBV has been advocated by multiple research groups and mandated by recent legislation in Congress, the Center for Disease Control and Prevention and AASLD each recommend slightly different guidelines. As part of the San Francisco Hep B Free campaign, we offered free serologic screening and vaccination, if appropriate, to over 2000 APIs between January and October 2008. Of the total number of participants screened (2,118), 72 (3.4%) were chronically infected. Of those people who reported previous vaccination, 90 (32.5%) lacked protective antibodies and 3 (1.1%) were actually chronically infected. Among the APIs screened, 64 (3.3%) were chronically infected with HBV. Of those not chronically infected, 993 (51%) lacked protective antibodies and were at risk for future infections. Men were 1.5 times as likely as women to be chronically infected. Adults aged sixty or older were three times more likely to be infected than people under the age of sixty. APIs born in endemic regions were 4.6 times more likely to be chronically infected than U.S.-born APIs. In an earlier study by Hutton et al., a Markov model of different screening strategies suggested that it is cost-effective to screen all APIs, irrespective of birthplace. To date, no studies have examined the rates of chronic infection in secondand third-generation APIs, i.e. U.S.-born APIs whose parents were born in Asia or the U.S. Based on an interim analysis of the San Francisco Hep B Free Campaign, we hypothesize that it is not cost-effective to screen all APIs given the lower prevalence rates in 2nd and 3rd generation U.S.-born APIs. We plan to integrate the data from our screening program with Hutton's model to re-evaluate costeffectiveness of HBV screening across different generations of APIs. Clearly, there is a need for identification of hepatitis B cases in the API community and vaccination when appropriate. By identifying non-traditional risk factors such as parental birthplace in U.S.-born APIs, we hope to make screening efforts more targeted, cost-effective, and successful.

W1811 HBV Screening in Asian Pacific Islander Americans: An Interim Analysis of the Hep B Free Program

Chronic hepatitis B infection affects approximately 400 million people worldwide, with a disproportionately high prevalence in Asian Pacific Islanders (APIs). HCC is the second leading cause of cancer deaths among APIA men. It is estimated that one in ten APIs is chronically infected with HBV. The guidelines set forth by various organizations lack consistency with regard to HBV screening in APIs. Although screening of all APIs for chronic HBV has been advocated by multiple research groups and mandated by recent legislation in Congress, the Center for Disease Control and Prevention and AASLD each recommend slightly different guidelines. As part of the San Francisco Hep B Free campaign, we offered free serologic screening and vaccination, if appropriate, to over 2000 APIs between January and October 2008. Of the total number of participants screened (2,118), 72 (3.4%) were chronically infected. Of those people who reported previous vaccination, 90 (32.5%) lacked protective antibodies and 3 (1.1%) were actually chronically infected. Among the APIs screened, 64 (3.3%) were chronically infected with HBV. Of those not chronically infected, 993 (51%) lacked protective antibodies and were at risk for future infections. Men were 1.5 times as likely as women to be chronically infected. Adults aged sixty or older were three times more likely to be infected than people under the age of sixty. APIs born in endemic regions were 4.6 times more likely to be chronically infected than U.S.-born APIs. In an earlier study by Hutton et al., a Markov model of different screening strategies suggested that it is cost-effective to screen all APIs, irrespective of birthplace. To date, no studies have examined the rates of chronic infection in secondand third-generation APIs, i.e. U.S.-born APIs whose parents were born in Asia or the U.S. Based on an interim analysis of the San Francisco Hep B Free Campaign, we hypothesize that it is not cost-effective to screen all APIs given the lower prevalence rates in 2nd and 3rd generation U.S.-born APIs. We plan to integrate the data from our screening program with Hutton's model to re-evaluate costeffectiveness of HBV screening across different generations of APIs. Clearly, there is a need for identification of hepatitis B cases in the API community and vaccination when appropriate. By identifying non-traditional risk factors such as parental birthplace in U.S.-born APIs, we hope to make screening efforts more targeted, cost-effective, and successful.

Amyotrophic lateral sclerosis in Finland: birthplaces of patients, parents and grandparents.

Amyotrophic lateral sclerosis (ALS) appears to be more prevalent in the southeastern part of Finland and among the war evacuees displaced from this area after the World War II than elsewhere in the country. A random sample of 31 ALS patients was chosen and the birthplaces of their ancestors traced back in two generations to find out whether there would be any tendency of clustering in certain regions of the country. No such trend was found. This finding speaks against a genetically determined tendency for the disease.

Inheritance of microtia in the Finnish population

To study the inheritance of microtia in the Finnish population, identify families for genetic linkage analyses and compare the phenotype between sporadic and familial patients. Retrospective case series and patient questionnaire of 109 microtia patients referred for reconstruction of the earlobe to the Helsinki University Central Hospital during the years 1980-2005. 22 out of the 109 patients had a relative with microtia or preauricular tag. The familial and sporadic patients did not differ in microtia phenotype or sex distribution. Urinary system anomalies were statistically more prevalent in familial patients (p<0.01). The analyses of the birthplace of parents or grandparents of familial or sporadic microtia patients resulted in no evidence for founder effect. The prevalence of familial microtia/OAVS in the Finnish population is higher than 20%. The sporadic and familial microtia/OAVS patients do not differ in the phenotype or sex distribution. The mode of inheritance seems to be autosomal dominant with incomplete penetrance.

Human DNA bank in Sao Miguel Island (Azores): A resource for genetic diversity studies

The peopling of São Miguel Island in the 15th century was made by Portuguese and settlers of foreign origin (Flemish, Jews, Moorish prisoners and black slaves), generating an admixture signature. Thus, to unravel São Miguel's population genetic background and to characterize its population's polymorphisms, we decided to establish a human DNA bank. Here, we describe the construction of the DNA bank and analyse the information of 997 samples obtained from healthy blood donors. The bank follows the international ethical guidelines, which include informed consent, confidentiality, anonymity of personal data, and abandonment in case of expressed will. DNA was isolated from blood samples, coded and immediately stored in a locked refrigerator. The identifiable DNA bank has self-reported data concerning sex, age, birth, current place of living, and parental birthplaces. The samples are representative of all the island's municipalities (r=0.995, p<0.01). The majority (87%) of the participants is male, with mean age of 36.3 years (18–64 years). Birthplace analysis reveals that 902 (90%) have both parents born in São Miguel. Moreover, 477 (54%) have their parents born in the same locality, confirming a relatively high rate of consanguinity in rural area. To date, this DNA bank was used to assess the Y-chromosome phylogeny and diversity in Azorean population. Now, we are analysing autosomal STRs for the better understanding of the gene pool and genetic structure of the archipelago's people.

Effects of familial risk factors and place of birth on the risk of autism: a nationwide register‐based study

The etiology of autism is unknown. A strong genetic component has been detected but non-genetic factors may also be involved in the etiology. We used data from the Danish Psychiatric Central Register and the Danish Civil Registration System to study some risk factors of autism, including place of birth, parental place of birth, parental age, family history of psychiatric disorders, and paternal identity. A total of 943,664 children younger than ten years were followed from 1994 to 2001; of those, 818 children developed autism. The highest risks of autism were found in siblings of children with autism, or Asperger's syndrome and other pervasive developmental disorders (PDDs), with relative risks of 22 and 13, respectively. The relative risk of autism in the child was about twice as high if the mother had been diagnosed with a psychiatric disorder. The risk of autism was associated with increasing degree of urbanisation of the child's place of birth and with increasing paternal, but not maternal, age. An increased relative risk of 1.4 was found if the mother was born outside Europe, and in children of parents who were born in different countries. The highest risk of autism was found in families with a history of autism, or Asperger's syndrome and other PDDs in siblings, supporting the commonly accepted knowledge that genetic factors are involved in the etiology of autism.