Many Arab countries have some of the highest rates of marriages between relatives in the world, especially marriages between first-degree cousins, which can reach 25-30% of all marriages. In some countries, such as Qatar, Yemen and the United Arab Emirates, kinship rates are rising in the current generation. Studies among Arabs and around the world indicate that consanguinity can affect some reproductive health parameters, such as postpartum mortality and rates of birth defects. The relationship of relatedness to other reproductive health parameters, such as fertility and fetal loss, is controversial. The main effect of consanguinity, however, is an increase in the rate of homozygotes for autosomal recessive genetic diseases. Worldwide, there are more known dominant disorders than known recessive disorders. However, data on genetic disorders in Arab populations from the Catalogue of Transmission Genetics in Arabs (CTGA) database indicate the relative abundance of recessive disorders in this region is clearly related to kinship practice.