It’s a common idea that marrying your first cousin is unhealthy, but only a few know the actual genetic risks. However, in almost half of the USA states, it is banned. The objection is based on genetic diseases such as cystic fibrosis, sickle-cell anemia, etc. But is there an actual risk of marrying your cousin?
Cousin marriage or consanguinity is one of the most deeply rooted social trends among one-fifth of the world population, mostly residing in West Asia, the Middle East, North Africa, and emigrants from these countries now living in North America, Europe, and Australia. Although public awareness on this social issue is letting people contemplate on cousin marriages, yet some communities won’t let go of their traditions that easily. People still need sound answers to their questions and awareness about the health risks of their children. Public health care providers need a detailed response to the very problem and should make this a part of their necessary counseling and training health program.
There was an unusual rise in autosomal recessive disorders among children mainly seen in the British Pakistani community. According to a study, approximately 140 different diseases have been seen in the local community, and the rate is mostly high in the Asian region, particularly Pakistan. The number of pediatric neurodegenerative conditions has risen from 8 in 1986 to 45 today. Moreover, despite the awareness that there is increased risk, most cousins who marry have healthy children.
To understand the whole process, first, you’ve to understand the process of inheriting your parents’ genes. It goes like this: each of us receives one copy of each gene from our parents. Thus, we receive two versions of each gene called alleles; one can be dominant and the other recessive. For a recessive gene to unmask itself, both copies of the gene should be recessive alleles. In the case of only one copy, one will be called a carrier who can pass on the gene or disease to his/her offspring. Whenever an individual gets two copies of a dangerous recessive allele, the respective gene will express itself, and he or she will manifest the disease. When two carriers of a recessive gene have a child, the child has a one-in-four chance of inheriting two copies of that gene. The likelihood of a couple having the same variant gene is one in a hundred in the general population. In cousin marriages, the risk can rise to one in eight because those related to each other are more likely to carry the same faults in their DNA.
Each carrier has a 50% chance of passing on the dangerous allele to their child. However, in the case of rare diseases, only a few individuals are carriers. The trouble in cousin marriage is that they both share common grandparents. Hence, the probability of inheriting the carrier gene from both parents increases compared to non-related marriages. There is a 50% chance that both parents will be carriers, ready to pass on two copies of dangerous alleles. To simplify, British researchers have simplified the estimated number and determined that the rate of an autosomal recessive disorder is approximately 6% in cousin marriages than non-related marriages in which is around 3%. It tells us that a genetic disorder’s chances are not entirely ruled out no matter what kind of marriage it is.
As per the Annual Review of Anthropology 2010, it is concluded that lower levels of consanguineous marriages should therefore result in a lower incidence of these increasingly common adult-onset diseases both in developed and developing countries. These include genetic disorders and other health conditions too, like blood pressure, cholesterol levels, etc. Hence, the closer the biological relationship between parents, the greater is the probability that their offspring will inherit identical copies of one or more bad recessive genes. However, in general, consanguinity does not increase the risk for autosomal dominant conditions in offspring when only one of the parents is affected.
But that doesn’t mean first cousins shouldn’t get married at all, or there must be any prohibitions. Scientists are also reporting today that first cousins can have children without any risks of genetic disorders as they didn’t find any particular reason to discourage cousin-marriage. The steaks of a genetic disorder are high, but there is no certainty about dangerous alleles’ unmasking. Sometimes they do express themselves; sometimes, they do not. There is no biological reasoning to verify that yet.
According to a report, in the general population, a child’s risk of being born with a genetic disorder like cystic fibrosis or spina bifida is 3 to 4 percent. Furthermore, a cousin marriage adds another 1.7 to 2.8 percent chance of the risk. Although the risk is significant, it is still not considered big enough to abolish cousin-marriage at all. Furthermore, 20 to 60 percent of all marriages are between close biological relatives in some parts of the world. As estimated by the BBC, 55 percent of Pakistan’s couples in Britain are married to their first cousins. To some people, it is like a custom or tradition close to their heart. They seek no happiness in defying their conventions. Well, it’s up to the choice of people whether they want to double the risk for their future generation or not.
Cousin marriages are a critical factor in an average of two child deaths every week. Thousands of others survive but with dreadful physical or mental conditions. These include blindness, deafness, blood ailments, heart or kidney failure, lung or liver problems, and several even untreatable neurological or brain disorders. And British Pakistanis are 13 times more likely to have genetic disorders than the general population. In Birmingham, around 1 in 10 children either dies at an early age or lives with a life-long disability caused by genetic deterioration. It is because half of the mothers of Pakistani origin are married to their first cousins. But according to some researchers, cousin marriage’s health effects have been greatly exaggerated so far.
Instead of making laws about abolishing cousin-marriage, there is a need for social awareness about preconception counseling. The new report says that genetic counselors should help couples who are first cousins as they help their other clients. They should take a thorough family history of the parents, look for any genetic disorder running in the family or their ethnic group, and order tests accordingly. During pregnancy, the woman should go through blood tests to screen for any neurological disorders and an ultrasound examination.
After the baby is born, he/she should be tested for deafness and certain rare metabolic diseases for which they already take tests for all newborns in some countries. However, children born to parents who are first cousins need special attention as these conditions have slightly more chances of occurring in them. Some of the metabolic diseases are treatable, and children with hearing loss can perform better over time if attended early.
Until Next Time,
Team Doctor ASKY!