<P> Comprehensive genetic education and premarital genetic counseling programs can help to lessen the burden of genetic diseases in endogamous communities . Genetic education programs directed at high - school students have been successful in Middle Eastern countries such as Bahrain . Genetic counseling in developing countries has been hampered, however, by lack of trained staff, and couples may refuse prenatal diagnosis and selective abortion despite the endorsement of religious authorities . In Britain, the Human Genetics Commission recommends a strategy comparable with previous strategies in dealing with increased maternal age, notably as this age relates to an increased risk of Down Syndrome . All pregnant women in Britain are offered a screening test from the government - run national health service to identify those at an increased risk of having a baby with Down syndrome . The HGC states that similarly, it is appropriate to offer genetic counseling to consanguineous couples, preferably before they conceive, in order to establish the precise risk of a genetic abnormality in offspring . Under this system the offering of genetic counseling can be refused, unlike, for example, in the US state of Maine where genetic counseling is mandatory to obtain a marriage license for first cousins . Leading researcher Alan Bittles also concluded that though consanguinity clearly has a significant effect on childhood mortality and genetic disease in areas where it is common, it is "essential that the levels of expressed genetic defect be kept in perspective, and to realize that the outcome of consanguineous marriages is not subject to assessment solely in terms of comparative medical audit". He states that the social, cultural, and economic benefits of cousin marriage also need to be fully considered . </P> <P> Higher total fertility rates are reported for cousin marriages than average, a phenomenon noted as far back as George Darwin during the late 19th century . There is no significant difference in the number of surviving children in cousin marriages because this compensates for the observed increase in child mortality . The total fertility increase may be partly explained by the lower average parental age at marriage, and age at first birth, observed in consanguineous marriages . Other factors include shorter birth intervals and possibly a lower likelihood of using reliable contraception . There is also the possibility of more births as a compensation for increased child mortality, either via a conscious decision by parents to achieve a set family size or the cessation of lactational amenorrhea following the death of an infant . According to a recent paper the fertility difference is probably not due to any underlying biological effect . In Iceland, where marriages between second and third cousins were common, in part due to limited selection, studies show higher fertility rates . Earlier papers claimed that increased sharing of human leukocyte antigens, as well as of deleterious recessive genes expressed during pregnancy, may lead to lower rates of conception and higher rates of miscarriage in consanguineous couples . Others now believe there is scant evidence for this unless the genes are operating very early in the pregnancy . Studies consistently show a lower rate of primary infertility in cousin marriages, usually interpreted as being due to greater immunological compatibility between spouses . </P> <P> Cousin marriages in the United Kingdom include Charles Darwin, Queen Victoria and John Granville Harkness . </P> <P> In royalty, marriage between cousins was common . King Phillip II of Spain, also husband of Queen Mary I of England, had first married his first cousin on both sides, Maria Manuela, Princess of Portugal . </P>

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