Consanguineous marriage, the union between closely related individuals, has been practiced for generations across various cultures. While such marriages provide socio-economic and cultural advantages, they also raise important medical concerns, particularly regarding the genetic health of offspring. In India, this practice is deeply rooted in tradition and approximately 9.9% of marriages are consanguineous. However, with growing awareness of genetic risks, it is essential to examine whether consanguinity genuinely increases the risk of genetic abnormalities in children
The genetics behind consanguineous marriages
From a genetic standpoint, consanguineous marriages increase the risk of autosomal recessive disorders. These disorders occur when both parents, carrying the same recessive mutation, pass it on to their child. In non-consanguineous unions, the chances of both partners having the same genetic mutation are relatively low. However, in consanguineous marriages, this probability is significantly higher
Autosomal recessive inheritance: Affected offspring will have unaffected parents who are carriers.
Several studies have shown a correlation between consanguinity and an increased risk of congenital anomalies, genetic disorders, and child mortality; for example, the odds of developing physical and mental disabilities, cardiovascular diseases, and hearing impairments increase in offspring from such unions.
Prevalence in India and Its implications
In India, the prevalence of consanguineous marriages varies by region, with higher rates observed in certain southern states. These unions are often preferred due to cultural beliefs in family unity, the preservation of property, and economic stability. However, studies in India, as well as in other regions with high rates of consanguinity, like the Middle East and North Africa, have consistently linked consanguineous marriages with a higher prevalence of genetic disorders such as thalassemia, cystic fibrosis, and congenital heart diseases
Global percentages of consanguineous marriages by country in representative consanguineous populations, Consanguineous marriage is a traditional and culturally respected practice in many communities across the globe, especially the Middle East, West Asia, and South India. This transverse region extends from Pakistan and Afghanistan in the east to Morocco in the west. Intrafamilial unions collectively account for 20–50% or more of all marriages in these areas. Among these, first-cousin marriages are particularly common, representing 20–30% of all marriages in certain populations.7
The link between consanguinity and major congenital malformations, such as nonsyndromic neural tube defects and cleft lip and/or palate, remains a topic of debate. However, after adjusting for confounding factors, studies have identified a significantly increased risk of specific congenital heart defects in the offspring of first-cousin marriages. This association may point to a recessive inheritance pattern, an influence on noncoding regulatory DNA, or the involvement of epigenetic mechanisms in the development of congenital heart defects. Despite this, a genome-wide linkage analysis conducted in South India—where uncle-niece and first-cousin marriages are highly prevalent—using high-density oligonucleotide microarrays failed to identify a single gene with a major effect in a clinically diverse group of cases born to consanguineous parents.
A study on consanguinity in the Souses population in Morocco revealed similar findings, with first-cousin marriages leading to increased incidences of physical and mental disabilities, as well as cardiovascular diseases. These findings mirror concerns raised in India, where genetic counselors and healthcare professionals have urged caution regarding consanguinity due to its potential health risks for offspring.
The reason behind close kin marriage
Close-kin marriage can serve as a strategy for preserving cultural values and ensuring cultural continuity, with cousin marriages offering strong opportunities for the transmission of these values. For this reason, consanguineous unions are often considered more stable than marriages between nonrelatives, though data on marital discord and divorce in such unions remain limited. In many Arab societies, patrilateral parallel cousin marriages are seen as crucial for strengthening ties within the same descent group and ensuring the education of children remains within the family. These factors may hold particular significance in times of social change or political and socioeconomic instability. Consequently, higher rates of close- kin marriage have been observed among certain minority ethnic groups, especially during the early stages of settlement by emigrant communities and refugees. In contrast, in South India and according to Confucian traditions in China, while marriage between a man and his mother’s brother’s daughter is permitted, patrilateral parallel cousin unions are considered incestuous.
The role of premarital genetic screening
To address these risks, several experts recommend premarital genetic screening and counseling for couples planning consanguineous marriages. Genetic counseling is particularly important in India, where awareness of the health risks associated with consanguinity is still limited. By understanding their genetic backgrounds, couples can make informed decisions about family planning and take preventive measures to reduce the risk of genetic abnormalities in their children.
Raising Awareness: Understanding the impact of consanguinity
While consanguineous marriages may continue to be favored in certain parts of India due to cultural and social reasons, it is essential to balance tradition with modern genetic knowledge. Raising awareness about the potential genetic risks, promoting genetic counseling, and providing access to premarital screening can help mitigate the health challenges associated with consanguinity. While not every consanguineous marriage results in genetic abnormalities, the increased risk of inheriting recessive genetic disorders is real and well documented. Studies consistently show that offspring from such unions have a higher chance of developing congenital conditions, disabilities, and other genetic disorders. In India, as in many other regions, the debate surrounding consanguineous marriage must shift from cultural preservation to ensuring the genetic well-being of future generations. By integrating scientific insights into traditional practices, we can better protect the health of children born to consanguineous unions while respecting cultural values. It is crucial to acknowledge the potential health implications and take preventive measures, such as genetic counseling and screening, to protect future generations.
References-
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- Khayat AM, Alshareef BG, Alharbi SF, AlZahrani MM, Alshangity BA, Tashkandi NF. Consanguineous Marriage and Its Association With Genetic Disorders in Saudi Arabia: A Review. Cureus. 2024 Feb 9;16(2):e53888. doi: 10.7759/cureus.53888. PMID: 38465157; PMCID: PMC10924896.
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- Unravelling the links between consanguinity and genetic diseases https://www.thehindu.com/sci-tech/science/unravelling-links-consanguinity-genetic-diseases-modern-genomics/article67395655.ece – Vinod Scaria.
- The Impact of Consanguinity on the Indian Population AH. Bittles https://tspace.library.utoronto.ca/html/1807/23525/hg02010.html
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- Bittles AH . The global prevalence of consanguinity, 2010. Available at: http://www.consang.net. Accessed December 1, 2010.
- Dahbi, N., El khair, A., Cheffi, K. et al. Consanguinity, complex diseases and congenital disabilities in the Souss population (Southern Morocco): a cross-sectional survey. Egypt J Med Hum Genet 25, 27 (2024). https://doi.org/10.1186/s43042-024-00490-w
- Hamamy, H., Antonarakis, S., Cavalli-Sforza, L. et al. Consanguineous marriages, pearls and perils: Geneva International Consanguinity Workshop Report. Genet Med 13, 841–847 (2011). https://doi.org/10.1097/GIM.0b013e318217477f