Cousin Marriages: A Medical Student’s Evidence-Based Response to Common Misconceptions

Cousin marriage, especially first-cousin marriage, is a widely practiced tradition in many parts of the world, including South Asia, the Middle East, and North Africa. In societies where it is normalized, it is often defended strongly, not only by families, but even by some healthcare professionals. It’s not uncommon to hear statements like:

Cousin marriage is usually safe.

Other communities like Hindus and Christians have genetic disorders too.

The risk only appears after 4–5 generations.

Only rare conditions like thalassemia are a concern.

Since Islam allows it, it must be safe.

As a medical student, I believe it is essential to address these misconceptions using undeniable scientific facts, population genetics, and a responsible interpretation of Islamic ethics.

Claim 1: "Cousin marriage is usually safe, so there's no reason to resist it."

Truth: It may not always cause harm, but it certainly increases risk.

Science does not claim that cousin marriage is always dangerous, but it does state that it significantly increases the risk of passing on autosomal recessive disorders, especially when practiced repeatedly in families.

Why?

Every human carries 4–5 faulty recessive genes on average. If two unrelated people marry, the chance of both carrying the same faulty gene is low.

But first cousins share 12.5% of their DNA, which makes it more likely that both carry the same mutation.

🔬A 2013 study in The Lancet showed that children of first-cousin couples had double the risk of congenital anomalies compared to non-related couples.

🔬 According to the British Medical Journal (BMJ), the risk of infant death, birth defects, and disability increases by 2 to 3 times in consanguineous marriages.

Cousin marriage is not inherently forbidden or universally harmful, but it is medically riskier than unrelated marriages, especially if there's a family history of disease.

Dr. Alan Bittles 

Australian geneticist and consanguinity expert (Centre for Comparative Genomics, Murdoch University) said that: 

The increased risk of autosomal recessive disorders in consanguineous marriages is real and quantifiable. Repeated cousin marriages can double or triple the risk of inherited diseases in a community.

Dr. Bittles has published extensively on the subject, including in The Lancet and WHO publications.

Claim 2: "Hindus and Christians also have disorders. So cousin marriage doesn’t make a difference."

Truth: All populations have disorders, but cousin marriage increases the rate and frequency of inherited conditions.

This argument ignores the core issue: the statistical risk of inherited disorders rises in communities that commonly practice cousin marriage. In outbred populations (non-related marriages), genetic diversity lowers the chance of two people having the same faulty gene.

In inbred populations, the same mutations circulate through families, increasing the risk of serious diseases.

For example, Pakistan has one of the highest rates of cousin marriages (60–70%), and as a result, inherited conditions like thalassemia, metabolic disorders, intellectual disabilities, and genetic deafness are far more common compared to populations that avoid cousin marriages.

This is a numbers game, not a cultural debate.

Dr. Daghni Rajasingam

Consultant obstetrician and spokesperson, Royal College of Obstetricians and Gynaecologists (UK)

Increased risk of genetic abnormalities in babies born to first cousins is a major public health issue in communities where cousin marriage is common. — (BBC interview, 2013)

She has been part of NHS campaigns that promote genetic screening in at-risk communities.

Claim 3: "Genetic disorders only happen after 4–5 generations of cousin marriage."

Truth: That is completely false. Genetic disorders can appear in the first generation of cousin marriage.

This is one of the most dangerous and unscientific claims being spread, even by some doctors.

If both cousins are silent carriers of the same recessive mutation, the chance of having an affected child is 25% in every pregnancy.

This can happen in the very first cousin marriage, not just after multiple generations.

Diseases like phenylketonuria, Fanconi anemia, and retinitis pigmentosa have been reported in first-generation cousin marriages, not fifth.

In fact, repeating cousin marriage across generations only worsens the genetic pool, compounding the problem over time.

Dr. Qaiser Malik

Consultant obstetrician & gynecologist, UK (originally from Pakistan)

As doctors, we must look beyond cultural sensitivity when we are risking a child’s future. Cousin marriage is not a religious obligation—it’s a social practice that has very real consequences for genetic health. (From a public health campaign in Bradford, UK—where cousin marriage is prevalent.)

Claim 4: "Only a few rare diseases like thalassemia are linked to cousin marriage."

Truth: Thalassemia is just the tip of the iceberg.

It’s misleading to suggest only one or two conditions are of concern. The list of recessive disorders that become more common in cousin marriages is extensive and includes:

1. Beta-thalassemia
2. Sickle cell anemia
3. Spinal muscular atrophy
4. Congenital deafness
5. Cystic fibrosis
6. Metabolic disorders (e.g., Tay-Sachs, GSD)
7. Retinal dystrophies
8. Intellectual disability syndromesThese disorders can be devastating, requiring lifelong treatment, specialized care, or resulting in early death.

Many hospitals in South Asia are witnessing increased pediatric admissions for rare inherited disorders in areas where cousin marriage is common.

Dr. Areej Hassan

Pediatrician and researcher in hereditary conditions in Middle Eastern populations

What many families don’t realize is that just one cousin marriage, without any previous family history, can still result in a child being born with a serious disorder. The risk is not just theoretical—it’s being seen in hospitals every day. (Statement in a WHO regional health seminar)

Claim 5: "Islam allows cousin marriage, so it must be safe."

Truth: Islam allows it, but it does not guarantee it's safe or advisable in every case.

Yes, cousin marriage is permitted (mubah) in Islam, but Islam also teaches:

• To avoid harm (لا ضرر ولا ضرار)
• To seek knowledge and wisdom (أَفَلَا تَعْقِلُونَ)

To protect future generations

The Prophet Muhammad ﷺ said:

No harm shall be inflicted or tolerated. – (Sunan Ibn Majah)

Islam gives freedom of choice, not a blanket medical approval. Just like eating sweets is allowed in Islam, but if you’re diabetic, it becomes dangerous....context and consequences matter.

Avoiding cousin marriage based on medical advice is not un-Islamic, it’s wise and responsible, and perfectly in line with the objectives of Shari’ah (Maqasid al-Shariah), which prioritize protection of life and lineage.

Cousin marriage may be legal, religiously allowed, and culturally accepted, but none of those make it medically safe.

Dr. Anwar T. Al-Awadhi

Kuwaiti obstetrician and member of GCC Genetic Disorder Council

 In our region, cousin marriage is common—but so are inherited disorders. Islam allows cousin marriage, but it also demands us to prevent harm. We must balance tradition with medical responsibility. (From a panel on genetics and reproductive health in Gulf countries)

As a medical student, my duty is to stand by science, evidence, and public health. We must:

• Encourage genetic counseling before cousin marriages
• Spread awareness about recessive disorders
• Educate families without disrespecting culture or religion
• Protect the health of future generations through informed decisions.

 Tradition shapes identity, but knowledge shapes destiny. Let’s respect our values, but follow the facts.

WHO (World Health Organization)

Consanguinity increases the prevalence of rare genetic disorders and congenital malformations. This is a public health concern in many communities. — (WHO Eastern Mediterranean Health Journal, 2009)