consanguinity and its relevance to genetic diseases

Each cell in our body contains 23 pairs of chromosomes (a total of 46 chromosomes), one copy from our father and the other from our mother. These chromosomes are in charge of determining our eye shape, hair color, traits, and health.

We usually have 5 or more recessive genes in our bodies, which may cause genetic diseases in our offspring by 25% even if we don't have any symptoms.
But does this always imply that a child has a genetic disease? Does consanguineous marriage associated with an increased risk of genetic diseases?

In this article, we will discuss how genetic diseases are transmitted to children, the role of consanguineous marriage in increasing the chances of children procuring genetic diseases, and the importance of genetic testing before marriage and pregnancy in prevention and treatment.

Transmission of genetic diseases from parents to children

As previously stated, we inherit one copy of our genes from our father and the other copy from our mother. If both the father and mother have the same genetic mutation that causes a genetic disease, the following are the expected outcomes:

• Having a healthy baby by 25%
• Having a child who carries a copy of the gene with the disease-causing mutation and another healthy copy by 50%
• Having a sick child who carries two copies of the gene with the disease-causing mutation by 25%

These possibilities do not always imply having children with genetic diseases or being carriers of genetic mutations that cause genetic diseases.

However, we should be aware that not all genetic mutations that we carry cause genetic diseases or have negative health consequences. Some of them are harmless mutations that have no effect on health.

Does consanguinity increase risk of genetic disorders?

Consanguineous couples share approximately 50% of their genes, which means they are more likely to carry the same genetic mutations that cause one of the genetic diseases in their children, and thus the risk of developing genetic diseases and premature death among children increases by 5%, compared to 2-2.5% among children from non-consanguineous marriages. In addition to increasing the chances of miscarriage and stillbirth.

 consanguinity and genetic diseases

Consanguineous marriage increases the likelihood of children developing many genetic diseases, most notably:

Birth defects

The proportion of children with birth defects in consanguineous marriages rises from 3% to 6%. Impaired hearing, hereditary heart diseases, and chromosomal abnormalities are examples of these abnormalities (such as Down syndrome, Turner syndrome, Edwards syndrome, and others).

sickle cell disease

Consanguineous marriage raises the risk of sickle cell anemia by 40%-50%. It is a genetic disorder that causes red blood cells to deform into sickles or crescents, reducing the amount of oxygen transported to all parts of the body and causing complications. Along with other genetic blood diseases like thalassemia and hemophilia.

Also read: Sickle cell anemia

Cystic fibrosis (CF)

It is a genetic disorder that affects the sweat and mucus glands, as well as the pancreatic ducts, resulting in thick secretions that affect the lungs and digestive system, as well as increasing the risk of dehydration, diabetes, osteoporosis, and male infertility.

Tay-Sachs disease

It is a genetic disorder that causes fatty acid accumulation in the brain and nervous system due to the loss of the enzyme responsible for breaking down fatty acids, hexosaminidase A, and thus affects growth and leads to muscle weakness, blindness, hearing loss, paralysis, and epilepsy over time. It usually appears around the age of 5.

Obesity

Obesity increases the risk of developing type 2 diabetes, heart disease, insulin resistance, and other health problems. Consanguineous marriage nearly triples the risk of children developing genetic obesity.

Consanguineous marriage also increases the risk of rare genetic diseases, cancer, fragile X syndrome, spinal muscular atrophy, and other genetic diseases.

The importance of genetic testing before marriage and pregnancy

 Premarital and prenatal genetic testing for those who are about to marry or become pregnant, as well as testing before or after childbirth, is necessary to protect your health and the health of your family from genetic diseases.

 The American College of Obstetricians and Gynecologists recommends carrier screening for the following:

• People who are about to marry and have children.
• Pregnant women.
• Prospective couples, or couples with family history with genetic diseases.

Genetic testing is also recommended in the following situations:

• Delayed pregnancy.
• Experiencing recurrent miscarriages - 2 or more.
• Having a child with a genetic disease to ensure that the second pregnancy is healthy.
• A child dying before the age of one year.

Genetic consultation is also required for those who are about to marry and become pregnant in order to determine the possibility of children suffering from genetic diseases based on the family history of genetic diseases in the husband and wife's families, and to recommend the appropriate genetic examination and provide recommendations for preventive or therapeutic options.

Enigma Genomics offers MyPremaritalCare before marriage and pregnancy, which examines more than 550 genetic diseases, in addition to prenatal genetic testing packages such as; NIPT test.

In conclusion, genetic testing and genetic consultation before marriage and pregnancy are necessary to protect your family from genetic diseases, especially if the marriage is a consanguineous marriage.