The Haemoglobinopathies in Europe. The problems inherent in this type of calculation may be illustrated by reference to Africa and America. In Africa there are some remarkable limitations in the information available. For instance, there has been no good large-scale survey of the frequency of thalassaemia in Egypt, while the Sudan illustrates the difficulty of dealing with a large country. Since the frequency of sickle cell trait varies greatly, with a minimum towards the East and a maximum towards the West,but there has been no micro-mapping, it is impossible to make even reasonable estimates of the number of affected births for the whole country.
Consanguineous marriage is common in North Africa.
It has been estimated that this marriage pattern approximately doubles the birth-rate of affected children in the countries where it is common. Most offspring of consanguineous marriages would be homozygous for the gene in question. However, in the absence of fuller information about this population, actual figures for the births of thalassaemic children have not been proposed. It probably occurs with alow frequency in other countries in addition to the Ivory Coast, Liberia, Upper Volta, Guinea and Guinea Bissau. In North America information on haemoglobinopathies among the black population is sound.