How cousin marriages raise the risk of genetic disorders in children

While culturally accepted, intra-family marriages can double the risk of genetic disorders, say experts, calling for greater awareness and preventive care

In many communities, marriages within the family, mostly among cousins, are seen as a way to preserve tradition and strengthen bonds. However, what often goes unspoken is the role genetics plays in shaping the health of future generations. 

While these unions may feel familiar and safe, experts warn they can carry hidden medical risks. As awareness grows, doctors urge families to look beyond tradition and consider the science.

What happens when close relatives have children

At the heart of the concern lies how genes are inherited. Every individual carries a mix of healthy and faulty genes. However, most of the time these do not cause problems because a healthy gene compensates for the faulty one. 

 

The challenge arises when two closely related individuals have a child, as they are more likely to carry the same faulty gene. This increases the chances that the child may inherit two copies of that gene, which can lead to what are known as autosomal recessive disorders. 

As Dr Madhukar Bhardwaj, director & HOD, neurology, Aakash Healthcare, explains, "Intra-family marriages increase the chance that both partners will have the recessive gene mutation, which can significantly raise the risk of genetic disorders in their children."

How much higher is the risk?

According to Dr Bhardwaj, the risk of birth defects does increase in intra-family marriages, and this rise is medically recognised. 

“In the general population, the risk of birth defects is around two to three percent. However, in marriages between cousins, this risk increases by about two to two-and-a-half times,” he explains. 

While the absolute numbers may still seem small, experts stress that the increase is significant from a public health perspective, especially in communities where intra-family marriages are common. 

According to experts, the risks are often underestimated or not discussed openly. Cultural acceptance, combined with limited access to genetic counselling, means many couples are unaware of potential consequences. 

Dr Bhardwaj highlights the broader concern, stating, "While the risk may seem low for a couple, at a community level it becomes a significant public health concern. It is not about blaming practices but about empowering families with knowledge."

Health problems linked to cousin marriages

Children born to closely related parents are more likely to face a range of health challenges. These are not limited to one condition, but can affect multiple aspects of development and overall health. 

Some commonly reported issues include:

• Birth defects and congenital anomalies
• Intellectual disabilities and developmental delays
• Metabolic disorders
• Hearing and vision problems
• Higher rates of stillbirth and infant mortality

"Research from India also shows that intra-family marriages are linked to rates of miscarriages, preterm births and developmental delays," says Dr Bhardwaj.

Why the degree of relation matters

The level of genetic risk is closely tied to how closely related the parents are.

• First cousins carry higher risk than distant relatives
• The closer the biological relationship, the greater the chance of shared genes
• Generations of intra-family marriages can compound risks over time

This means that in families where such marriages are repeated, the likelihood of inherited disorders may gradually increase.

The Indian context: Awareness still limited

Consanguineous marriages are not uncommon in India. "Estimates suggest that around 10 percent of marriages involve blood relatives, with higher prevalence in southern states," shares Dr Bhardwaj. 

Despite this, awareness regarding genetic risks remains low. Many families may not perceive a problem because they have seen healthy children born in similar circumstances. 

Experts believe this leads to a false sense of security. Even if outcomes appear normal in some cases, the underlying genetic risk does not disappear.

What can help reduce the risk

Healthcare professionals emphasise on making informed choice. Several preventive steps can significantly reduce risks:

• Genetic counselling to help couples understand their individual risk
• Carrier screening tests to identify shared genetic mutations
• Prenatal testing to detect certain conditions during pregnancy
• Newborn screening for early diagnosis and treatment

Awareness campaigns tailored to specific communities can also play a crucial role in improving understanding.

Finding a balance between culture and science

Experts stress that the conversation must remain sensitive and respectful. Simply advising against intra-family marriages may not be effective and could alienate communities. Instead, the focus should be on education and voluntary screening. 

As Dr Bhardwaj notes, "Genetic counselling and screening can help identify risks early and guide couples toward safer reproductive choices. The key is to strike a balance—respect traditions while ensuring that scientific evidence is communicated clearly." 

With better awareness, access to genetic services, and culturally sensitive communication, families can be empowered to make choices that prioritise both tradition and the health of future generations. 

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This report is for informational purposes only and is not a substitute for professional medical advice.