SELECTED STUDIES

Consanguineous marriages in the Arab World

 By Prof. Hanan Hamamy, MD
National Centre for Diabetes, Endocrinology and Genetics, Amman, Jordan

 
Consanguineous marriages are marriages contracted between blood relatives. According to the World Health Organization Guidelines, a consanguineous marriage is defined as a marriage between people who are second cousins or more closely related.  It is estimated that globally about 20% of the human population live in communities with a preference for consanguineous marriage, and that at least 8.5% of children have consanguineous parents [1]

Global consanguinity rates

Consanguineous marriages occur in most populations, with varying percentages among all marriages (Fig 1).

Population types favoring consanguineous marriages include:

·        Populations in the Middle East, North Africa, South West Asia and South India where total consanguinity rates range between 20-50+% of all marriages

·        Populations in South America, China and Japan where consanguinity rates range between 1-10% of all marriages

·        Small population isolates where inbreeding is common. These account for a very small percentage of the world population (e.g. Amish).

·        Recent migrants from Pakistan, India, the Middle East, North Africa and South West Asia who become permanent residents in Europe, USA and Canada. (e.g. Maghrebians in France, Turks in Germany, Pakistanis in the U.K.)

Consanguinity rates among Arabs

Among Arabs, consanguineous marriages are customary and constitute 20-50% of all marriages. First cousin marriages constitute almost one third of all marriages in many Arab countries (Table1). The rates of these marriages differ between countries as well as within one country. Marriages between first cousins are favored culturally and socially and considered the “usual” or “expected” pathway in life for first cousins whether they were reared in close proximity or reared far apart.

 Table (1): First Cousin Marriages among Arabs

 
 Reasons for marrying a cousin

Consanguineous marriages are favorably looked upon among Arabs for one or more of the following reasons:

• Consanguineous marriage is more favorable for the women’s status. The wife would have better relationship with her in-laws and could be protected by them in time of need

• There is a general belief that marrying within the family reduces the possibilities of hidden uncertainties.

• Premarital negotiations regarding financial matters of marriage are more easily conducted

• Consanguinity strengthens family ties, and enforces family solidarity.

• Landlords prefer to keep their property within the family

• The husband and wife share the same social relationships after marriage as before marriage.

• Wife’s parents prefer to have their daughter living near them and to enjoy the presence of their grandchildren.

 
Factors influencing population consanguinity rates:

Several factors may have an influence on the consanguinity rates in Arab countries. These factors include urban/rural residence of families within the country, education levels of parents, religion, and time trend.

 For example, in Jordan, it was evident that the higher the level of education of the female partner, the lower the consanguinity rate. The same level of education for men did not minimize their choice for marrying a cousin [8](Fig 2).  In Yemen, Jurdi [16] confirms the inverse association between consanguineous marriages and women’s education, whereas higher educated men were more likely to be married to cousins. 

Consanguineous marriages are culturally customary among Arabs, with higher rates of first cousin marriages among Muslims than among  Christians (Fig 3)

Reports from some Arab countries have also shown that consanguinity rates are higher in rural as compared to urban settings (Fig 4)

Contrary to what might be expected, the consanguinity rates in at least some Arab countries is not decreasing in the present generation as compared to previous generations (Fig 5). In Yemen, the prevalence of consanguineous marriages appears to have increased over time [16]. Among Muslim Arabs in Israel, rates of first cousin mating were stable over time, in contrast to the significant decrease in the rates of distant consanguineous mating [17]. However, another study among the Israeli Arab community revealed a significant decrease in the frequency of consanguineous marriage from 52.9% in the period 1961– 1970 to 32.8% in the period 1991–1998 [7]. In Algeria, consanguinity rates seem to be increasing in present generation only in rural settings, they remain more or less stable in urban settings [3]

Why are consanguinity rates not declining in some Arab countries?

Ø      Consanguinity is a deeply rooted cultural trend

Ø      The practice is seen as promoting family stability and having significant social and economic advantages

Ø      With improvement in health, there will be more relatives to intermarry.

Ø      The adverse genetic effects on health do not affect 90% of all related marriages.

 
What factors may decrease consanguinity rate?

Higher maternal education

Lower fertility

More mobility from rural to urban

Better economic status of families

Prof. Samia Temtamy (Egypt)

Dr. Sadika A. Al-Awadi (Kuwait)

Prof. Mohsen Al-Hazmi (Saudi Arabia)

Dr. Anna Rajab (Sultanate of Oman)

Prof. Ahmed S. Teebi (Canada)

Consanguinity and reproductive health

Reproductive criteria related to consanguineous couples versus non-consanguineous include:

·        Earlier parental age at marriage

·        Younger maternal age at first live birth

·        Higher number of infants born to consanguineous parents

·        Lower rates of primary sterility

·        Same or lower rates of abortion

·        Higher rates of postnatal mortality in offspring

·        Higher rates of congenital malformations in offspring

• Higher risk of having offspring with autosomal recessive disorders if such a gene is segregating in the family

When genetic counseling is offered to families with a segregating autosomal recessive condition, some points which may be observed include:  

o       In some families advice on limiting further intermarriages in the family faces many difficulties. The decision could involve many members in the family.

o       Counselling against cousin marriages when there is an autosomal recessive condition in the family may not be welcomed, because nobody wants to admit to others that the family is harbouring a ‘bad’ gene

o       The term “hereditary disorder” may arouse feelings of hostility and denial, leading to refusal of medical advice.

o       Response to genetic counseling depends more on the educational level and understanding of the parents, than upon the severity of the disease.

In net terms, consanguinity was not found to be associated either with a significant positive or negative effect on fertility [18]. Among the offspring of consanguineous marriages worldwide, there is an increased postnatal mortality rate and an increased frequency of congenital malformations [19]. Similar results were obtained from studies conducted among Arabs [6,9,10,20-25]. A recent study suggested that having consanguineous parents seems to decrease the risk of breast cancer especially in younger women [26].

What consanguineous marriage means to the public in general

Arabs culturally and socially favor consanguineous marriages. They are at times more stable than marriages between non-relatives. The husband’s family would side with the wife in marital disputes since she is considered a part of the extended family. When there are children with disabilities, the family ties strengthen more so that everybody has a share in caring and rehabilitating these children. Parents, grandparents, aunts and uncles are frequently seen together in visits to genetic clinics. Advise against cousin marriage at the population level may disrupt family ties and interfere with the care given to genetically disabled children [1].

In the minds of lay people, consanguinity is linked to congenital malformations, mental retardation and disability. However the concepts of inheritance is not clear. For example, some may think that inherited disorders are only linked with cousin marriages from the paternal side, that is the fathers of the couple are brothers. Sometimes cousin marriages are avoided when the disease is autosomal dominant. Education of the public in general and of primary health personnel is an important first step in clarifying the advantages and disadvantages of consanguinity in the population [27,28].

Reports from Arab countries on consanguinity rates may sometimes include marriages between third cousins or far relatives within the consanguineous category. Although this discrepancy affects the total consanguinity rate, it does not markedly alter the average inbreeding coefficient. However, standardized methodologies and guidelines in conducting studies on consanguinity among Arabs are needed to validate comparisons between the various geographical, ethnic and socio-economic groups studied [27]

In 1994 and 1996, the World Health Organization’s Regional Office for the Eastern Mediterranean held meetings to review the place of genetics in medical services in the Region. The participants agreed that consanguineous marriage is an integral part of cultural and social life in many areas, and that attempts to discourage it at the population level are inappropriate and undesirable, even though it is associated with an increased birth prevalence of children with recessive disorders. Instead, they recommended an approach that identifies families at increased risk and provides them with genetic counseling. They pointed out that this approach could be unusually effective in populations that favor consanguineous marriages [1,28]

References

1. Modell B , Darr A. Genetic counseling and customary consanguineous marriage. Nature Reviews Genetics ,2002 ;3:225-229.

2. Bittles AH. Consanguinity and its relevance to clinical genetics.Clin Genet ,2001; 60: 89–98.

3. Zaoui S, Biemont C.  [Frequency of consanguineous unions in the Tlemcen area (West Algeria)] [Article in French]  Sante ,2002 ;12(3):289-95

4. Al-Arrayed S. The frequency of consanguineous marriages in the state of Bahrain. Bahrain Medical Bulletin, 1995;2:63-67.

5. Hafez M, El-Tahan H, Awadalla M, El-Khayat H, Abdel-Gafar A, Ghoneim M. Consanguineous matings in the Egyptian population . J Med Genet ,1983 ;20(1):58-60

6. Hamamy H., Bayati N, Kubaisy W. Consanguineous marriages in the Iraqi urban population and the effect on pregnancy outcome and infant mortality. Iraqi Medical Journal,1986;34;75-79

7. Jaber L, Halpern GJ, Shohat T. Trends in the frequencies of consanguineous marriages in the Israeli Arab community. Clin Genet, 2000; 58: 106–110

8. Khoury SA, Massad D. Consanguineous marriage in Jordan. Am J Med Genet ,1992 ;43(5):769-75.

9. Al-Awadi SA, Moussa MA, Naguib KK, Farag TI, Teebi AS, el-Khalifa M, el-Dossary L.  Consanguinity among the Kuwaiti population. Clin Genet ,1985 May;27(5):483-6

10. Khlat M. Consanguineous marriage and reproduction in Beirut. Am J Med Genet, 1988, 43:188-196

11. Rajab A, Patton MA . A study of consanguinity in the Sultanate of Oman. Ann Hum Biol ,2000;27(3):321-6

12. Zlotogora J. Genetic disorders among Palestinian Arabs: 1.Effects of consanguinity. Am J Med Genet, 1997;68(4);472-5.

13. al-Abdulkareem AA, Ballal SG. al-Abdulkareem AA, Ballal SG. J Community Health 1998 ;23(1):75-

14. El-Hazmi M, Al-Swailem AR, Warsy A,  Al-Swailem AM, Sulaimani R,Al-Meshari A. Consanguinity among the Saudi Arabian population. J Med Genet, 1995;32:623-626

15. al-Gazali LI, Bener A, Abdulrazzaq YM, Micallef R, al-Khayat AI, Gaber T.  Consanguineous marriages in the United Arab Emirates. J Biosoc Sci ,1997 Oct;29(4):491-7

16. Jurdi R, Saxena PC. The prevalence and correlates of consanguineous marriages in Yemen: similarities and contrasts with other Arab countries. J Biosoc Sci, 2003;35(1):1-13

17. Vardi-Saliternik R, Friedlander Y, Cohen T. Consanguinity in a population sample of Israeli Muslim Arabs, Christian Arabs and Druze  .Ann Hum Biol, 2002;29(4):422-31.

18. Bittles AH, Grant JC, Sullivan SG, Hussain R. Does inbreeding lead to decreased human fertility? Ann Hum Biol ,2002;29(2):111-30

19. Bittles A. reproductive behaviour and health in consanguineous marriages. Science,1991;252:788-794.

20. Khoury SA, Massad DF. Consanguinity, fertility, reproductive wastage, infant mortality and congenital malformations. Saudi Med J. 2000;21(2):150-154.

21. Bittar Z. Major congenital malformations presenting in the first 24 hours of life in 3865 consecutive births in south of Beirut. Incidence and pattern. J Med Liban, 1998;46(5):256-60

22. Rajab A, Vaishnav A, Freeman NV, Patton MA. Neural tube defects and congenital hydrocephalus in the Sultanate of Oman. J Trop pediatr,1998;44(5):300-3.

23. Abdulrazzaq YM, Bener A, al-Gazali LI, al-Khayat AI, Micallef R, Geber T. A study of possible deleterious effects of consanguinity. Clin Genet, 1997;51(3):167-73.

24. Khrouf N, Spang R, Podgorna T, Miled SB, Moussaoui M, Chibani M. Malformations in 10,000 consecutive births in Tunis. Acta Pediatr scand, 1986;75(4):534-9.

25. Hamamy H, Al-Hakkak Z. Consanguinity and reproductive health in Iraq. Human Heredity,1989;39:271-275.

26. Denic S, Bener A. Consanguinity decreases risk of breast cancer--cervical cancer unaffected. Br J Cancer 2001 Nov 30;85(11):1675-9

27. Hamamy H, Alwan A. Hereditary disorders in the Eastern Mediterranean Region. Bull World Health Org, 1994; 72(1):145-54.

28. Alwan, A. A. & Modell, B. Community Control of Genetic and Congenital Disorders. EMRO Technical Publication Series 24 (WHO Regional Office for the Eastern Mediterranean Region, Egypt, 1997).

Further Readings:

Teebi, AS. & Farag, TI (eds.). Genetic Disorders Among Arab Populations. New York: Oxford University Press, 1997.

Prof. Hanan Hamamy, MSc(Edin), MD is a distinguished medical geneticist with a plethora of published papers. She is one of the founders of community genetics. Email: hhamamy@hotmail.com

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