Socio-cultural factors, such as maintenance of family structure and property, ease of marital arrangements, better relations with in-laws, and financial advantages relating to dowry seem to play a crucial role in the preference of consanguinity in Arab populations [3]. Consanguineous marriages are generally thought to be more stable than marriages between non-relatives, though there are no studies to compare divorce rates of consanguineous and non-consanguineous marriages among Arabs. It is generally believed that the husband's family would side with the consanguineous wife in marital disputes since she is considered part of the extended family. When there are children with disabilities, more family members share in caring for these children. Unlike what is thought, consanguinity in the Arab World is not only confined to Muslim communities. Several other communities, including the Lebanese, Jordanian, and Palestinian Christian populations, have also practiced consanguinity, but to a lesser extent than Muslims [4–7].

Consanguinity rates show wide variations among Arab countries, as well as within the same country (Table 1, Additional file 1). However, 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. Therefore, for comparison of consanguinity rates among populations, two parameters are best used; the mean inbreeding coefficient (F) and marriages between first cousins. However, Arab societies have a long tradition of consanguinity, and the cumulative estimate of (F) may exceed the estimated value which is calculated for a single generation [8].

Secular changes in the consanguinity rates have been noticed in some Arab populations. In Jordan [9], Lebanon [5], Bahrain [10], and among Palestinians [11–13], the frequency of consanguineous marriage is decreasing. Several factors may be playing a role in decreasing the consanguinity rates in Arab countries. Amongst these factors are the increasing higher female education levels, the declining fertility resulting in lower numbers of suitable relatives to marry, more mobility from rural to urban settings, and the improving economic status of families. Moreover, genetic diseases may be feared more now that infectious diseases are on the decline as causes of severe morbidity and mortality.

Generally, the highest rates of marriages to close relatives are consistently reported in the more traditional rural areas and among the poorest and least educated in society [8]. Reports from some Arab countries have shown that consanguinity rates are lower in urban when compared to rural settings. Urban to rural first cousin rates in Algeria were 10% and 15% [14], in Egypt, 8.3% and 17.2% [15], and in Jordan, 29.8% and 37.9% [6], respectively. Likewise the mean inbreeding coefficient was lower in urban as compared to rural settings in Syria (0.0203 versus 0.0265) [16]. In Jordan, it was evident that the higher the level of education of the female partner, the lower the consanguinity rate. Only 12% of university educated females would marry their first cousins, whereas 25% of university educated males tend to marry first cousins [6]. Similar trends of lower consanguinity rates among educated women, but not educated men, were noticed in Yemen [17] and Tunisia [18].

On the other hand, social, religious, cultural, political and economic factors still play roles in favoring consanguineous marriages among the new generations just as strongly as they did among the older generations, particularly in rural areas. Consanguinity rates seem to be increasing at a higher pace in Qatar [19], Yemen [17], the United Arab Emirates (UAE) [20], and Tlemcen in Algeria [14]. In Morocco, a study indicated an increasing consanguinity rate from the previous (21.5%) to the present (25.4%) generation [21], while another study indicated a decreasing consanguinity rate [22]. Consanguinity rates are not declining in some Arab countries because it is generally accepted that the social advantages of consanguinity outweigh the disadvantages [23], and consanguinity is regarded as a deeply rooted cultural trend. It is believed that the practice of consanguinity has significant social and economic advantages. Consanguineous marriages among Arabs are respected because it is thought that they promote family stability, simplify financial premarital negotiations, offer a greater compatibility between the spouses and other family members, offer a lesser risk of hidden financial and health issues, and maintain the family land possessions [3, 24, 25]. Among 390 women attending reproductive health clinics in Jordan, consanguinity was protective against violence during pregnancy [26]. In all cases, reports on secular trends in consanguinity need to be treated with some caution because in countries where consanguinity is favored, major regional and ethnic differences in prevalence are commonly observed [3].