Most Inbred Countries: Cousin Marriage Rates and Genetic Risk

You have probably seen a ranked list, or a shaded world map, that claims to name the most inbred countries, and the phrase sounds like a judgment on a whole people. What those lists actually count is cousin marriage, still preferred in parts of Pakistan, the Middle East, and North Africa, and uncommon in much of Europe and the Americas.

The short answer is that those lists put Pakistan first and then a band of Arab countries, while the studies behind a single country often spread across a wide range. This page puts the list figure next to that range, shows what pushes a family toward the high or low end, and spells out the extra health risk that belongs to a first-cousin couple rather than to a nationality.

How Is Cousin Marriage Counted in Country Lists?

In clinical genetics, a consanguineous marriage is a union between people who are second cousins or closer. Among Arab families that group includes double first cousins, first cousins, first cousins once removed, and second cousins. Parent-child and brother-sister unions are a different category, and they are not what these country percentages measure.

About 20% of the world’s people live in communities that prefer this kind of marriage. The share is highest across North Africa, the Middle East, and parts of West and South Asia, and the same custom continues in some families from those regions after they move.

HOW CLOSE THE RELATIONSHIP IS

• Second cousins: This is the furthest tie that still counts in the clinical definition, at an inbreeding coefficient of 0.0156.
• First cousins: The parents share about 12.5% of their genes, and their child is expected to carry identical copies at 6.25% of gene loci.
• Double first cousins: The coefficient rises to 0.125, the same level reached by an uncle-niece marriage in communities where that union is practiced, including parts of South India.

When you compare countries, the first-cousin column is the fairer one, because some overall rates also count third cousins and distant kin from the same tribe. That wider net lifts the headline percentage without moving the average inbreeding coefficient by much. Lists that print one number per country rarely tell you which net they used.

Where Do the Most Inbred Countries Sit?

Public lists put Pakistan first, at 61.2%. A 1990s comparison of a Karachi sample and the Pakistan Demographic and Health Survey reported 58.7% and 62.7%, with mean inbreeding coefficients of 0.0316 and 0.0331, and more than 80% of those cousin marriages were between first cousins. The famous 61.2% sits inside that older survey pair. It is not a head count from this decade.

The ranges beside the other high countries come from a 2009 review of consanguinity among Arab populations. Where a public list prints one percentage, the review often prints a low and a high from different studies. Blank first-cousin cells mean that review did not give one.

Read a whole row before you trust a rank. Saudi Arabia is the clearest mismatch: the list figure sits below every overall rate in the 2009 review. Oman and Libya show the same kind of gap. Nubia’s very high band belongs to that region, not to Egypt as a whole, and South Sudan’s 50% is the Sudan figure repeated because the two were measured together.

Why Do Cousin Marriage Percentages Disagree?

A country can look “most inbred” on one chart and ordinary on the next because the surveys are not the same project. They sample different years, cities, and clinics, and some of them count distant relatives that others leave out. The mean inbreeding coefficient and the first-cousin rate were built for that problem. The single overall percentage was not.

BAHRAIN, OLDER REVIEWS AND LATER NEWBORNS

• Older review: Overall consanguinity runs from 39.4% to 45.5%, and the first-cousin figure in that table is 24.5%.
• Four months of 2008: Among parents of newborns, total consanguinity was 10.9% and first-cousin marriage was 6.9%.
• All of 2009: Total consanguinity was 11.4% and first-cousin marriage was 6.8%, inside a Bahrain study of 2008 and 2009 newborns covering 14,237 babies.
• The drop: First-cousin marriage fell from 24% to nearly 7% over about ten years, without a campaign that told people to stop marrying cousins.

A list that still prints Bahrain near 31.8%, or inside the old 40% band, is recycling the earlier studies. The same freeze is why Pakistan is still introduced at 61.2% decades after those surveys. Treat any undated country rank as a clipping from whatever paper the compiler had, then look for the year.

What Raises or Lowers Cousin Marriage Rates?

Inside one country the rate moves with place and schooling, which is why a national percentage is a poor guide to your own family. In a Jordan study, 12% of university-educated women married a first cousin, compared with 25% of university-educated men. The same pattern, a lower rate among educated women and a weaker link for educated men, also shows up in Yemen and Tunisia.

Families give practical reasons for staying with a cousin: holding property in the family, an easier wedding to arrange, kinder relations with in-laws, and less pressure around the dowry. The 2009 review also treats these marriages as socially respected, including the belief that a wife’s own relatives will side with her in a dispute. Those are social reasons. They are not a medical finding that the marriage is safer.

The direction of change is not one-way. In that 2009 review, cousin marriage was falling in Jordan, Lebanon, Bahrain, and Palestinian communities, and it was rising in Qatar, Yemen, the UAE, and Tlemcen in Algeria. Morocco produced both results: one study moved from 21.5% in the previous generation to 25.4% in the generation then surveyed, and another study found a decline. Where women spend longer in school, where families leave villages, and where fewer children grow up as eligible cousins, the pool of customary matches shrinks.

Health Risks Tied to First Cousin Marriage

A high country rate does not assign you a personal risk. The figure counselors use belongs to the couple, and it is an increase on top of the risk every pregnancy already carries. Cousin marriage matters most for rare recessive conditions, the ones that appear only when a child inherits the same faulty gene from both parents.

Figures Counselors Use for First Cousins

The 2009 review says the birth-defect multiples still need tighter studies in Arab countries before anyone treats them as exact. Cleft lip and some heart defects show a link with cousin marriage in some Arab studies and no link in others. One Oman series found an overall rate of congenital heart defects similar to rates reported in Europe and America, and that result does not say whether cousin and non-cousin marriages inside Oman differed.

Miscarriage is a weak place to look for an effect. Several Arab studies find no clear difference in pregnancy loss between related and unrelated couples, while some report more live births among first-cousin couples, a pattern that fits with marrying younger and having a longer childbearing span. In a Beirut household survey, gaps in births and in child deaths disappeared once income, religion, and how long the marriage had lasted were taken into account.

Recessive Disorders That Cluster in Families

Because the parents already share ancestors, a gene that is scarce in the wider population can be common inside one extended family. A child of first cousins is more likely to receive two copies of that gene. The same marriage does not, by itself, create a new mutation.

• Bardet-Biedl syndrome
• Meckel-Gruber syndrome
• Spinal muscular atrophy
• Osteopetrosis with renal tubular acidosis
• Sanjad-Sakati syndrome
• Congenital chloride diarrhea

Those conditions are among the ones described as especially present in Arab populations, either across a wide area or inside particular towns and tribes. The catalogue of genetic disorders in the region lists far more recessive conditions than dominant ones, and a Jordan clinic series found blood relatives far more often among parents of children with recessive disease than among parents of children with other genetic conditions. A gene can sit quiet in a family for generations and appear when two carriers from that family marry.

What to Do Before a Cousin Marriage

Couples in these communities already ask a blunt question. In counseling guidance on cousin marriage, Hanan Hamamy records it as “Will our children be physically or mentally abnormal?” The useful answer starts from the family tree, not from a country rank: any relative with a known recessive illness, a child who died early without a clear cause, or a couple who are closer than first cousins, including double first cousins.

WHAT TO LINE UP BEFORE THE WEDDING

• The timing: On a Ministry of Health page updated 8 July 2026, couples in Saudi Arabia are asked to test at least three months before the marriage date.
• The certificate: A compatibility certificate from that program is valid for six months.
• The tests: Saudi premarital screening for blood disorders covers sickle cell anemia, thalassemia, hepatitis B, hepatitis C, and HIV.
• Where: More than 300 centers across Saudi Arabia offer the visit, and the government service is free.

About 90% of Saudi couples who were told they could have a child with sickle cell disease or beta-thalassemia still married, because of stigma or because the wedding could not be cancelled. That is the practical reason to screen before the date is fixed, not the week of the ceremony. Similar carrier programs operate in Jordan, Iran, Iraq, Bahrain, and Turkey, and Iran’s programs have reduced births of the blood disorders they target. Screening finds specific carrier states. It does not certify that a cousin marriage is free of every recessive risk.

Frequently Asked Questions

Does Islam Require Cousin Marriage?

Cousin marriage is not a religious duty. Christian communities in Lebanon, Jordan, and Palestine have also practiced it, at lower rates than their Muslim neighbors, and uncle-niece marriage is prohibited in Islam and does not show up in Arab surveys. Families describe the draw as keeping property close, making the wedding easier to arrange, and staying on good terms with in-laws.

Does Cousin Marriage Raise the Risk of Down Syndrome?

No link shows up in most of the counseling literature. Cousin marriage does not add risk for an autosomal dominant condition when one parent is already affected, and it does not add risk for an X-linked condition when neither parent is affected.

What Is a Double First Cousin?

A double first cousin couple is what you get when two siblings from one family marry two siblings from another, so the partners share both pairs of grandparents. The inbreeding coefficient for their child is 0.125, twice the 0.0625 coefficient for a child of ordinary first cousins.

Are Children of First Cousins Usually Healthy?

Yes, most are. A figure used in counseling starts from a background rate near 2.5% and moves it to about 5%, and a separate estimate puts the added chance of a congenital defect at 1.7 to 2.8 percentage points above the usual background. The extra cases are real, and they are still a minority of births.

Do Emigrant Families Keep Cousin Marriage?

Cousin marriage continues among emigrant communities from Pakistan, Turkey, North Africa, and Lebanon who live in Europe, North America, and Australia. A chart of countries does not stop applying when a family changes its address. The family history travels with the couple, which is why a counselor still asks where the grandparents were from.

The country rank tells you how common cousin marriage was in the surveys behind that rank. For a couple, the decision sits in their own pedigree and in a carrier test done before the wedding date is locked. A list that prints one percentage for a whole country cannot answer that question.

Disclaimer: This article is an educational guide to published research on cousin marriage rates and the health risks tied to them. It is informational only and is not medical, genetic, or legal advice. Talk with a qualified genetic counselor or physician before you decide on marriage, carrier testing, or a pregnancy. Figures and screening rules reflect the sources cited here and can change when newer surveys and health policies are published.