The prevalence of consanguineous marriages in an underserved area in Lebanon and its association with congenital anomalies

Background: Consanguinity is a recognized common practice among marriages in the Middle East. Many studies have suggested a strong association between first cousin marriages and the incidence of autosomal recessive diseases and congenital anomalies. The objectives of this study were to study the prevalence of consanguinity among the marriages of Bekaa (a region in Lebanon) with its sociodemographic correlates, and to assess the prevalence of congenital anomalies associated with these marriages. Methods: This study was a cross-sectional study done in three of the major areas of the Bekaa region. The sample size consisted of 552 households chosen based on proportionate random sampling according to population size in each area. The survey was conducted based on face-to-face interview with a member of the couples of each household. Results: The overall prevalence of consanguineous marriages was reported to be 42% with first cousin marriage constituting around 31% of the total marriages. No association was found between different socioeconomic status (SES) correlates and first cousin marriages. Results showed a significant association between first cousin marriage and mental retardation, physical retardation, bilateral cleft lip +/- cleft palate, cystic fibrosis, and congenital blindness. Conclusion: In a population with a high degree of inbreeding, the formulation of a public health program with multiapproach strategy, including education about the anticipated genetic consequences, prenatal diagnosis, neonatal screening, and genetic counseling, is a necessity.     

Prevalence and sociodemographic correlates of consanguineous marriages in Turkey

The aim of this study was to determine the prevalence and sociodemographic correlates of consanguineous marriages in Turkey using data derived from the 2003 Turkey Demographic and Health Survey (TDHS-2003). Demographic surveys conducted in the last 40 years consistently show that Turkey is a country with a high level of consanguinity. In the latest demographic survey (TDHS-2003), a nationally representative sample of 8075 ever-married women, consanguineous marriages accounted for 22% of the total, which is equivalent to a mean coefficient of inbreeding (alpha) of 0.011. There are changing secular profiles in the rates of consanguinity in general and of the specific sub-types of cousin marriages in particular in Turkey. The prevalence of first cousin marriages among all consanguineous marriages presents a steady decline from one marriage cohort to the next. The changes observed over time may be attributable to several factors such as the increase in educational level of women, the nuclearization of the family system, the mobility from rural to urban settings, a better socioeconomic status of families, an increase in women's labour force participation in formal sectors, lower fertility rates resulting in a smaller number of cousins available for marriage, and an increased awareness of the effects of consanguineous unions on child health in cases where there is an inherited recessive disease in the family. Any attempts to discourage consanguinity at the population level appear to be inappropriate and undesirable, especially when the consanguineous union remains an integral part of the cultural and social life of Turkey. Nevertheless the WHO-recommended approach to minimizing the negative effects of consanguinity on child health should be followed, i.e. the identification of families with a high risk of a genetic disease and the provision of prospective genetic counselling.     

The practice of consanguineous marriage in oman: prevalence, trends and determinants

The practice of consanguineous marriage has been the culturally preferred form of marriage in most Arab and the Middle Eastern countries, including Oman, but due to a paucity of population-based data in the past there is a dearth of information about its form and dynamics in Oman. Recent national-level surveys allow this gap to be filled. This paper examines the prevalence, trends and determinants of consanguineous marriages in Oman using data from the 2000 Oman National Health Survey. The results indicate a very high prevalence of consanguineous marriage in Oman, as more than half (52%) of marriages are consanguineous. First cousin unions are the most common type of consanguineous unions, constituting 39% of all marriages and 75% of all consanguineous marriages. The study observed various patterns of consanguinity, some of them common with other Arab nations, and some unique in nature. Women's age at marriage, employment, place of childhood residence and geographical region appear to be significant determinants of consanguineous marriages. Consanguineous marriage shows a strong association with marital stability, early age at marriage and early-age childbearing. There has been no appreciable change in the prevalence of consanguineous unions in Oman over the last four decades despite massive socioeconomic development and modernization. However, recent marriage cohorts show slight declining trends. The results suggest that consanguinity is likely to remain stable in the future or decline at a slow rate. Specific health education and genetic counselling should be followed in line with WHO recommendations to minimize the negative health consequences of consanguinity for child health.     

Consanguineous marriage in a newly developed country: the Qatari population

This study examines the frequency of consanguineous marriage and coefficient of inbreeding in the State of Qatar. The study was conducted in semi-urban areas of Doha between January and May 2004. A sample of 1515 married Qatari females aged 15 years and over participated. The degree of consanguinity between each female and her spouse, and degree of consanguinity between their parents were recorded. The rate of consanguinity in the present generation was high (54.0%) with a coefficient of inbreeding of 0.02706. The commonest type of consanguineous marriage was between first cousins (34.8%). Double first cousin marriages were common (3.1%) compared with other populations. The consanguinity rate in the State of Qatar has increased from 41.8% to 54.5% in one generation.     

Consanguineous marriage and differentials in age at marriage, contraceptive use and fertility in Pakistan

Fertility rates in Pakistan have remained consistently high over the past three decades. While numerous studies have examined sociodemographic determinants, the role of biological factors, and particularly consanguinity, has received little attention, even though marriage between close biological relatives continues to be the norm in Pakistan. Reproductive behaviour among women in consanguineous (first cousin) and non-consanguineous unions was compared, using data from a 1995 study of multi-ethnic communities in Karachi and the 1990-91 Pakistan Demographic & Health Survey (PDHS). The results show that, although female age at first marriage has been gradually rising in both study samples, women in consanguineous unions married at younger ages and were less likely to use modern contraceptive methods. In the Karachi sample, women in first cousin unions experienced a higher mean number of pregnancies and also reported a higher mean number of children ever born (CEB). However, their mean number of surviving children did not differ from those born to women in non-consanguineous unions, implying higher prenatal and/or postnatal losses in couples related as first cousins. On the other hand, the PDHS showed both lower CEB values for women in consanguineous marriages and a lower number of surviving children. Given the continuing popularity of consanguineous marriage, these findings have important implications for future fertility reduction in Pakistan.     

Consanguineous marriages in Afghanistan

The present cross-sectional study was done in order to illustrate the prevalence and types of consanguineous marriages among Afghanistan populations. Data on types of marriages were collected using a simple questionnaire. The total number of couples in the study was 7140 from the following provinces: Badakhshan, Baghlan, Balkh, Bamyan, Kabul, Kunduz, Samangan and Takhar. Consanguineous marriages were classified by the degree of relationship between couples: double first cousins, first cousins, first cousins once removed, second cousins and beyond second cousins. The coefficient of inbreeding (F) was calculated for each couple and the mean coefficient of inbreeding (α) estimated for each population. The proportion of consanguineous marriages in the country was 46.2%, ranging from 38.2% in Kabul province to 51.2% in Bamyan province. The equivalent mean inbreeding coefficient (α) was 0.0277, and ranged from 0.0221 to 0.0293 in these two regions. There were significant differences between provinces for frequencies of different types of marriages (p<0.001). First cousin marriages (27.8%) were the most common type of consanguineous marriages, followed by double first cousin (6.9%), second cousin (5.8%), beyond second cousin (3.9%) and first cousin once removed (1.8%). There were significant differences between ethnic groups for the types of marriages (χ2=177.6, df=25, p<0.001). Tajiks (Soni) and Turkmens (also Pashtuns) showed the lowest (α=0.0250) and highest (α=0.0297) mean inbreeding coefficients, respectively, among the ethnic groups in Afghanistan. The study shows that Afghanistan's populations, like other Islamic populations, have a high level of consanguinity.     

The prevalence and correlates of consanguineous marriages in Yemen: similarities and contrasts with other Arab countries

Using data on 9762 women from the 1997 Yemen Demographic and Maternal and Child Health Survey, this paper examines the prevalence and socioeconomic correlates of consanguineous marriages in Yemen. The results indicate that 40% of marriages are consanguineous, over 85% of which are between first cousins. The prevalence of consanguineous marriages appears to have increased over time, particularly for the last marriage cohort. As for socioeconomic correlates, the study confirms the inverse association between consanguineous marriages and women's education and occupation, age at marriage and economic status. However, no statistically significant difference in the prevalence of consanguinity has been found by place of residence and geographical region. Somewhat unexpected results have been obtained by husband's background characteristics, with higher educated men and those working in the modern sector of the economy being more likely to be married to cousins.     

The changing profile of consanguinity rates in Bahrain, 1990-2009

Consanguineous marriage is traditional and respected in most communities of North Africa, the Middle East and West Asia, including Bahrain, with intra-familial unions accounting for 20-50+% of all marriages. Significant secular changes in consanguinity rates have been reported in recent decades in different populations. Among parents of 14,237 newborns in Bahrain in 2008-2009, the total consanguinity and first cousin marriage rates over a period of four months in 2008 were 10.9% and 6.9% respectively, while during all of 2009 the rates were 11.4% and 6.8% respectively. The study confirms that over a ten-year period first cousin marriage rates in Bahrain have declined from 24% to nearly 7%. Although advice against cousin marriages was not attempted at any stage in the comprehensive community genetics programmes in Bahrain, increasing the literacy of the public and of the health care providers on prevention strategies for genetic diseases could have contributed to this decline in consanguinity rate in Bahrain.     

Parental consanguinity as a cause for increased incidence of births defects in a study of 238,942 consecutive births.

The risk for birth defects in the offspring of first-cousin matings has been estimated to increase sharply compared to non consanguineous marriages. As a general decline in the frequency of consanguineous marriages was observed in this century, one wonders whether consanguinity is still a factor in the appearance of birth defects in developed countries. Based on our registry of congenital anomalies we tried to answer to this question. In the population studied in North-Eastern France a consanguineous mating was known in 1.21% of the cases with congenital anomalies, vs. 0.27% in controls, (p < 0.001). The frequency of the malformations recorded paralleled the degree of consanguinity: out of 89 malformed children, 51 were seen in first-cousins mating (10.3 times more frequent than in offspring of non consanguineous couples), 17 in second-cousins marriages and 18 in more distant relatives mating. Three were uncle-niece marriage. Excluding known mendelian conditions these numbers were 73, 36, 17 and 17 respectively and the corresponding relative risk were 3.68, 3.01, 3.41 and 4.89 respectively. Therefore there is a negative dose-response effect between level of inbreeding and risk of congenital malformations. Consanguineous mothers were more often pregnant than non consanguineous mothers (p < 0.01) and they had more stillbirths than non consanguineous mothers. These results show that consanguinity is still a factor of birth defects and they must be taken into account for genetic counseling of inbred marriages, in developed countries.     

Inbreeding pattern and reproductive success in a rural community from Galicia (Spain)

The present paper is based on information on marital patterns and reproductive performance (reconstituted families) in the rural community of Los Nogales, Galicia, Spain. Biodemographic data were used to analyse temporal changes and structure of consanguinity in the population, as well as consanguinity versus reproductive success. Of 2347 marriages celebrated between 1871 and 1977, 5.15% were between relatives (up to third degree). The population's inbreeding coefficient was above the Spanish average after 1890, and levels were high during the first part of the 20th century. A possible underestimation of inbreeding coefficients is attributed to the elevated frequency of extramarital births occurring in the Los Nogales population (13.47%). The structures of consanguineous matings, expressed as C22/C33 and C33/C44, turned out to be 0.86 and 0.82 respectively. Regarding migration, before 1920 consanguinity increased, but net migration was negative. In the period 1920-1929 consanguinity began to decrease, prior to maximum emigration. As for reproductive success, information from 1503 reconstituted families shows that complete fertility was slightly higher among consanguineous families despite a greater infant mortality. Lower infertility in consanguineous matings, as well as lower age at marriage and first maternity, could explain the above results.     

Consanguineous marriage in the capital city Sana'a, Yemen

Consanguineous marriage is traditionally common throughout the Eastern Mediterranean region, especially in the mainly Muslim countries. To date, there is little information on consanguinity in Yemen. The aim of this study was to ascertain the rate of consanguineous marriage and average coefficient of inbreeding in Sana'a City, Yemen. A population survey was conducted with the intention of covering married couples resident in Sana'a City by means of a multi-stage random sampling technique. A total of 1050 wives and husbands were interviewed on consanguinity in their households. The total incidence of consanguinity was 44-7% (95% CI 41.7-47.7%) with first-cousin marriages constituting 71.6% of the total consanguineous marriages and 32% of all marriages. Paternal parallel first cousins (Type I) accounted for 49% of first-cousin marriages. The average coefficient of inbreeding (F) was 0.02442. The incidence of consanguinity is relatively high in Yemen with predominantly first-cousin marriage. This might be related to the deeply rooted social and cultural beliefs in the country.     

Consanguineous marriage among the Fulani

The Fulani are a broad ethnic category of nomadic and seminomadic pastoralists and agropastoralists living in the semiarid Sahel region of sub-Saharan Africa. The Fulani are patrilineal, patrilocal, and moderately polygynous, with arranged first marriages accompanied by the payment of bridewealth, ideally in the form of cattle. Consanguineous marriage is frequent, with first or second cousin marriage preferred. In this paper we present data on levels of consanguineous marriage among the Fulani of northern Burkina Faso and test the hypothesis that inbreeding may be more frequent when there is a scarcity of cattle available, since bridewealth demands are thought to be reduced with close-kin marriage. Among 308 women's marriages, 203 (65.8%) were between kin up to and including second cousins, and 102 (33.1%) were between nonkin. Among 276 men's marriages, 196 (71.0%) were between kin up to and including second cousins, and 77 (27.9%) were between nonkin. The mean population inbreeding coefficient (alpha) was 0.0355 for women, and 0.0374 for men. No increase was found in population levels of inbreeding estimated from marriages contracted after the droughts of 1973 and 1984, which drastically reduced the Fulani's cattle stocks. However, a significantly higher rate of consanguineous marriage was found in families owning the fewest cattle.     

Estimates of cousin marriage and mean inbreeding in the United Kingdom from 'birth briefs'

From 626 ascendant genealogies, known as 'birth briefs', deposited by members of the Society of Genealogists in their London library, rates of consanguineous marriage and coefficients of mean inbreeding (a) of offspring were estimated for cohorts of marriages contracted in the late nineteenth and early twentieth centuries. The rate of first cousin marriage in the generation estimated to have married during the 1920s was 0.32%, with no marriages between second cousins. The mean inbreeding coefficient for the offspring of these marriages was estimated as 0.0002. In the previous generation 1.12% of the marriages were between first cousins, and the estimate of mean inbreeding was 0.0007. Comparison with data taken from the published literature suggests that the levels of cousin marriage observed are consistent with a secular decline during the late nineteenth and twentieth centuries.     

Trends of consanguineous marriages in a Sunni Muslim population of West Bengal, India

The Muslim population of the Chaltaberia village in the district of South 24 Parganas in West Bengal is divided into several wards (paras) inhabited by people of specific surnames. The frequency of endogamous marriages within surnames is greater than randomly expected ones. An incomplete reproductive isolation is observed among the five dominant surnames. Consanguineous marriages occur more often outside the village than inside. Leaving out marriages between long distances, a small median distance of 6.36 km is recorded. The neighborhood area works up to be 552.2 km2, which is rather small. There is an underlying process of breeding isolation by distance. A generation length of 21 years has been used for examining the temporal change in consanguineous marriages and inbreeding, which generally appears to increase. There is a general trend of decline in consanguineous marriages towards the southern part of West Bengal and eastern part of Assam among the Bengalee Muslims. The frequency of consanguineous marriages is 7.3% out of all marriages (N=1153) that have taken place in six generations in the population. The first cousin marriage is nearly 50% of all marriages. Patrilineal marriages are common in marriages between second and third cousins. An increase of consanguineous marriages in the younger generation was observed, but the total frequency agrees with a general trend of a decline in the frequency of consanguineous marriages among the Muslims in this part of India.     

Migration as a determinant of marriage pattern: preliminary report on consanguinity among Afghans

Two sample populations, one refugee and one resident, were studied. The frequencies of consanguineous marriages came out to be 49.8%and 55.4%, respectively, for the refugees and the residents. Caste endogamy was dominant both in the residents and the refugees. The mean coefficient of inbreeding was calculated to be 0.0303 for the refugee population and 0.0332 for the resident population samples. First cousin marriage was the dominant type of marriage in both samples; father's brother's daughter (FBD) marriage was more frequent among the refugees while mother's brother's daughter(MBD) marriage was more frequent among the residents. Education has no decreasing effect on the incidence of consanguineous marriages. A significant difference in the pattern of marriages in the refugees is observed after the Saur Revolution of 1979.     

Ancestral consanguinity and mortality among three endogamous populations of Chittoor District, Andhra Pradesh, India

Consanguineous marriages have been practiced around the globe by many societies from time immemorial, particularly in South India. Consanguineous marriages play a major role in the health of a population, and diseases leading to mortality of the progeny are a consequence of detrimental recessive genes. To evaluate the effects of ancestral consanguinity on mortality in relation to consanguineous marriage, we have ascertained data from 1,500 women belonging to three endogamous communities (Akuthota Reddy, Odde, and Madiga) of Chittoor District, Andhra Pradesh, India. There were 500 women from each community. For each marriage we drew a family pedigree, extended upward to two earlier generations on either side of the spouses, to determine the prevalence and pattern of consanguinity, with detailed information on fertility and mortality. We observed a significant difference in the mortality rates between consanguineous and nonconsanguineous marriages when all the marriages of the women, women's parents, and (women's) husband's parents were considered in all three communities. In inbreeding, the offspring of earlier generations might have passed on deleterious genes to later generations (under unfavorable conditions), which resulted in a negative aspect of reproduction (among the offspring of the present couple).     

Consanguinity, caste and deaf-mutism in Punjab, 1921

The effects of religion, population sub-division and geography on the prevalence of deaf-mutism were investigated using information collected in the 1921 Census of Punjab. The total sample size was 9.36 million, and comprised data on thirteen Hindu castes, seventeen Muslim biraderis and two Sikh castes. A two-way analysis of variance comparing males in Hindu castes in which consanguineous marriage was prohibited, with males in Muslim biraderis which favoured first cousin marriage, indicated major differences with respect to the patterns of deaf-mutism within each religion. In the Muslim population 9.1% of the relative variation in the prevalence of deaf-mutism was inter-biraderi, 36.8% between geographical regions, and 48.8% an interaction between biraderi and region, whereas among Hindus 46.8% of the observed variation was inter-caste, 12.8% inter-region and 33.6% due to caste region interaction. From a wider disease perspective the results obtained with the Hindu community indicate the significant genetic differentiation associated with caste endogamy. As the overwhelming majority of Hindu marriages continue to be within-caste, it can be predicted that similar levels of inter-caste differences in disease frequency currently exist. By comparison, the lower level of inter-biraderi variation among Muslims is probably indicative of the dissolution of pre-existing caste boundaries and the resultant gene pool mixing that followed the large-scale conversion of Hindus to Islam during Muslim rule in North India from the 13th to the 19th centuries.     

Isolation and marriage patterns in four South Tyrolean villages (Italy) during the nineteenth century

No information is currently available on the marriage patterns of German-speaking communities of the South Tyrol area. The aim of this study is to investigate the reproductive isolation of four South Tyrolean mountain villages during the 19th century. Data about 3953 marriages were drawn from existing pedigrees and completed with data from the parish registers of the studied villages to calculate the following indicators: age at marriage, endogamy, inbreeding from dispensations and from isonymy and repeated pairs of surnames among couples. The results show high levels of endogamy (78-87%) and an elevated age at marriage in all the studied villages. The percentages of consanguineous marriages (10-33%) vary considerably but result overall in relatively low inbreeding values (alpha 0.0015-0.0036; Ft 0.0098-0.0138). Levels of endogamy are consistent with the geographic characteristics of the area, while inbreeding values are lower than those observed in previous studies on Alpine communities. This is due to a low frequency of marriages between close relatives, probably related to the peculiar demographic and cultural characteristics of the studied populations that differentiate them from neighbouring Italian-speaking villages.