Prenatal diagnosis and genetic screening : community and service implications / a report of the Royal College of Physicians.

  • Royal College of Physicians of London.
Date:
1989
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Prenatal diagnosis and genetic screening : community and service implications / a report of the Royal College of Physicians. Source: Wellcome Collection.

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    Consanguinity Genetic risks related to maternal age in ethnic minorities Summary 4.16 British Pakistanis are in particular need of a genetics service because of their strong tradition of consanguineous marriage. The rate of first-cousin marriage among young British Pakistanis is 55%, compared with about 32% in Pakistan [40]. It would be inappropriate to try to interfere with this marriage custom, which is socially beneficial for women in the cultures where it is practised [41]. It does, however, have social and service implications. 4.17 Consanguinity increases the chance that two carriers of the same recessively- inherited condition will mate, and so it increases the birth-rate of children with recessively-inherited diseases, but it has no effect on dominant or X-linked disorders. There is probably a small increased risk of many multifactorial abnormalities, but even very common consanguineous marriage has a relatively small effect on the incidence of serious congenital disorders. Untrained health workers can inflict suffering by incorrectly telling parents that their consanguinity is the cause of their child’s illness. 4.18 On the other hand, traditional consanguineous marriage increases the pos sibilities for offering genetic counselling, because most large, highly consanguineous families actually transmitting a lethal recessive gene ultimately identify themselves by the birth of a homozygote. This child in turn then acts as a marker for an extended family cluster at very high risk. The appropriate strategy is to investigate and counsel the extended families of patients with serious recessively-inherited dis orders, and to encourage young related couples to attend for genetic counselling before starting their family. However, the problems of communication must first be solved. 4.19 For effective counselling, the woman must understand what is said, and must be able to ask questions. At present this means that British Pakistanis should be counselled by a female (ideally a Muslim) in the appropriate language, and at home if necessary. When these conditions are fulfilled, inheritance of disease can be understood, and first-trimester prenatal diagnosis is often requested [46]. A serious effort should be made to develop an appropriate approach to genetic counselling for all ethnic minorities. 4.20 Some ethnic groups still have large families where women continue child bearing almost to the end of their fertile life. At present, many such older mothers are not being appropriately counselled because it is assumed that they will not want karyotyping and because adequate provision is not made to overcome language difficulties. 54.1 In England at present about 5.5% of the population and 9% of births are in ethnic groups with specific genetic risks. People of Jewish origin are at increased risk of carrying Tay-Sachs disease, and many ethnic groups originating outside Northern Europe are at high risk of the haemoglobin disorders. It is cheap and easy to detect carriers of these disorders, and prenatal diagnosis, which is freely available at several national centres, is in high demand from informed couples at risk. The haemoglobin disorders in particular provide a good model of screening at the community level for inherited disease. However, because there is still no national policy, and screening and counselling are not regularly provided, the fall in the birth rate of affected children has been less than in Southern European countries. 54.2 The requirements for an adequate screening progamme for haemoglobin disorders include the recognition of specialist centres which should have associated ethnic genetic counsellors to act as a focus for a community service.