Consanguineous Marriage: Genetic Risks, Pregnancy Effects & Premarital Screening

In short: Consanguineous marriage is marriage between second cousins or closer relatives; it accounts for about 10.4% of marriages worldwide and up to 50% in some communities. It raises the risk of inherited diseases in children, such as thalassaemia, sickle-cell anaemia, cystic fibrosis and deafness, and of birth defects. Premarital medical screening for inherited blood diseases is therefore strongly advised.

Marriage is the foundation of a healthy family, and understanding your genetic health together as a couple can help protect your future children and give you greater peace of mind. This is why learning about consanguineous marriage — and considering premarital screening — matters for any couple planning a family.

Consanguineous marriage is a union between two individuals who are related as second cousins or closer.

Consanguineous marriages are common around the world and are estimated to make up about 10.4% of all marriages globally. That said, how common they are varies a great deal depending on the country and region.

Marriages between first cousins can represent up to 50% of unions within some communities. Marrying within an extended family carries deep cultural and even practical value in many societies. However, when these unions occur within a small family, community, or ethnic group, they can increase the chance of passing on genetic disorders that are otherwise rare in the wider population.

A study published on SpringerLink found that consanguineous marriage is associated with an increased risk of congenital physical conditions, as well as behavioral and mental health difficulties among children born from such unions. The study also noted that mental health concerns appear more frequently among women in consanguineous marriages.

There are several grades of relatives to be aware of:

• First cousin: He is the direct cousin of one of the parents

• Second cousin: He is the son of the cousin of one of the parents

• Third Cousin: He is the son of the first cousin of one of the parents or the son of the first cousin.

The closer the degree of relationship, the more DNA the individuals share — and this raises the likelihood of genetic conditions appearing in their children. For first cousins, the extra risk of a serious birth defect or genetic disease is about 2–3% on top of the 2–3% risk that every couple has, so most children of cousin marriages are healthy. The risk is higher if a genetic disease is already known in the family, and genetic counselling and carrier testing can help clarify it.

A genetic disease is defined as a condition that results from a change in the DNA sequence.

Related partners are more likely to carry the same hidden (recessive) gene change inherited from a common ancestor, which increases the chance that their child inherits two copies and develops a genetic disease or birth defect.

Dominant inheritance and recessive inheritance

Diseases that follow dominant inheritance occur when there is a problem in just one of the two copies of a particular gene — from either the father or the mother. This single change is enough for the person to develop the condition.

Diseases based on recessive inheritance, on the other hand, occur only when the problem is present in both copies of the gene — one from the mother and one from the father. In these cases, a single mutation is not enough to cause the disease.

The tricky part about recessive inheritance is that each parent may carry one copy of the mutated gene without any visible signs of disease. But if both copies come together in their child, the child may develop the condition — even though both parents appear completely healthy.

Conditions that may be more common with consanguineous marriage

• Increases the percentage of diabetes, hypertension and heart diseases

-Increased risk of infant death

-Intellectual disability and developmental delay caused by recessive genetic conditions.

• disorders in the digestive system
• Sickle cell anemia, which causes red blood cells to break down, leading to infarctions

-Mediterranean anemia (beta-thalassemia major), which causes severe anemia needing regular blood transfusions

• Exposure to polycystic kidney disease that leads to kidney failure and thus continuous dialysis.

-Thalassemia

-Infantile Cerebral Palsy

-Congenital deafness

-Cystic fibrosis

-Spinal muscular atrophy

-Tay-Sachs disease

-Multiple sclerosis

-Parkinson’s disease

-Spina bifida.

Consanguineous marriage and its relation to pregnancy

It may increase the risk of:

• miscarriages

-maternal anemia

• preeclampsia

-Vaginal bleeding

• premature birth

-increase in the rate of caesarean sections.

Premarital examination

A premarital medical examination helps identify certain hereditary blood diseases and some infectious diseases early, so couples can receive guidance about the possibility of passing these conditions on to their children — and learn about options that support planning for a healthy family.

The premarital medical examination program aims to:

• Reduce the spread of some genetic blood diseases (thalassemia - sickle cell disease) and some infectious diseases (hepatitis B / C).

• Help families avoid the social and psychological challenges that can come with raising a child with a disability.

• Reduce the financial burden associated with long-term treatment.

For these reasons, many specialists advise couples to avoid consanguineous marriage where possible, to help lower the chances of genetic diseases affecting their children and protect the long-term wellbeing of the family.

If you and your partner are planning a family and would like to better understand your genetic risk factors or discuss premarital and fertility screening options, the team at

These conditions are discussed further in our article on chromosomal abnormalities in pregnancy.

Dr. Najeeb Layyous clinic is here to guide you with compassionate, evidence-based care.

Dr Najeeb Layyous F.R.C.O.G

Consultant Obstetrician, Gynecologist and Infertility Specialist