NUR4636 University of West Florida Global Prevalence of Consanguinity Paper Define Consanguinity Identify global prevalence of consanguinity Describe imp
NUR4636 University of West Florida Global Prevalence of Consanguinity Paper Define Consanguinity
Identify global prevalence of consanguinity
Describe impact on population health risks
Discuss the cultural and ethical considerations of consanguineous unions
Write a 450 word essay using APA discussion qualities (excellent organization, grammar, spelling, citations, introduction, body and conclusion, 3 (or more) references no older than 5 years old). 11111
Fact Sheet 18 | WHEN PARENTS ARE RELATED CONSANGUINITY
When parents share a common ancestor, it is termed a consanguineous relationship and there is an
increased chance that they will both carry the same faulty gene variation. If both parents have the same
gene variation, there is an increased chance of having a child with a genetic condition.
In summary
We all carry certain genetic variations and faulty genes which do not usually
impact our health
Two unrelated people are less likely to carry the same faulty gene variation
People who are blood relatives share a greater proportion of the same genes
because they have a common ancestor
When parents are blood relatives, children have a slightly higher chance of
having a genetic condition.
WHAT IS CONSANGUINITY?
The word consanguinity comes from two Latin
words: con meaning shared and sanguis meaning
blood.
The
most
common
form
of
consanguineous relationship is between first
cousins and in some societies, can account for a
large proportion of relationships.
The reasons for promoting consanguinity in
certain communities are mainly social and include:
strengthening the family ties; retention of
property within a family and ease of finding a
suitable marriage partner.
Relationship to each other
RELATIONSHIPS BETWEEN BLOOD RELATIVES
Since our genetic information is passed down to us
from our parents and grandparents and so on,
people who are blood relatives will share a greater
proportion of the same genes than unrelated
people.
Genetic specialists have classified how close
relationships are considered, based on the
proportion of their genes that they share (Table
18.1). The closer the biological relationship is
between relatives, the more likely that they will
have a gene variation in common.
Relationship type
Proportion of genes they have in
common
Identical twins (monozygotic)
All (100%)
Brothers and sisters, non-identical
(dizygotic) twins, parents and children
First degree relatives (10)
Uncles and aunts, nephews and nieces,
grandparents and half-brothers and half
– sisters
Second degree
First cousins, half-uncles and aunts and
half-nephews and nieces
Third degree relatives (3 0)
Half (1/2, 50%)
Quarter (1/4, 25%)
relatives (20)
Eighth (1/8, 12.5%)
Table 18.1: Proportion of genes shared between close blood relatives
www.genetics.edu.au
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Fact Sheet 18 | WHEN PARENTS ARE RELATED CONSANGUINITY
Figure 18.1: Chromosome picture (karyotype) from a male
46,XY.
Figure 18.2: Autosomal recessive inheritance when both
parents are unaffected genetic carriers for the condition.
The faulty copy of the gene containing a recessive mutation
is represented by r; the working copy of the gene by R.
GENES AND CHROMOSOMES
Our bodies are made up of millions of cells. Each
cell contains a complete copy of a person’s
genetic instructions, or genes, packaged on
chromosomes. Chromosomes come in pairs,
giving two copies of each gene. The exception to
this rule applies to the genes carried on the sex
chromosomes called X and Y (Figure 18.1).
WHAT IS THE CHANCE OF HAVING CHILDREN
WITH A PROBLEM WHEN PARENTS ARE CLOSE
BLOOD RELATIVES?
If parents are unrelated, their chance of having a
child with a birth defect or disability is between
2% and 3%.
An autosomal gene is a gene located on a
numbered chromosome and usually affects males
and females in the same way.
An X-linked gene is located on the X or Y
chromosome and affects males and female
differently.
A variation that makes the gene faulty is called a
mutation or a pathogenic variant. Genes code for
the proteins our body needs to function. A
mutation in a gene will affect the body differently
depending on how much it changes the resulting
protein, how critical that protein is to the body
and how much of that protein is needed in the
body.
If parents are first cousins, the chance is a little
higher at 5% to 6%. This is due to the increased
chance that they will both carry the same
autosomal recessive mutation, passed down
through the family.
In general, when parents are consanguineous,
they do not have an increased chance of having a
child with genetic conditions that are due to Xlinked or autosomal dominant gene mutations.
However, there will be some increased chance of
a child inheriting conditions that are due to a
number of different genes acting together
(polygenic) or where there is an interaction
between genes and the environment such as
spina bifida and some forms of congenital heart
disease.
www.genetics.edu.au
Page 2 of 3
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Fact Sheet 18 | WHEN PARENTS ARE RELATED CONSANGUINITY
AUTOSOMAL RECESSIVE INHERITANCE
This type of inheritance refers to the inheritance
of a recessive gene mutation on an autosome
(one of the chromosomes numbered 1-22). See
Figure 18.2.
There are two copies of every autosomal gene.
Both copies of the gene send a message to the
cells to produce a particular product such as a
protein. Individuals who have a recessive
mutation on one gene, and a working copy of that
gene on the other partner chromosome, are said
to be genetic carriers of the mutation for a
particular condition.
Although only one of the gene copies is correctly
sending the instructions to make the gene
product, the cell can usually still work with this
reduced amount.
Genetic carriers for the great majority of
autosomal recessive genetic conditions do not
show any symptoms of the condition and do not
develop health problems due to being a genetic
carrier. As mentioned above, we all have a
number of recessive gene mutations which are
hidden due to the fact that we have a backup
working copy of the gene and therefore the
correct gene product is made.
If a person has both of their genes for a genetic
condition containing a recessive mutation, they
do not have the ability to make the correct gene
product and will have symptoms of the genetic
condition.
Therefore, for autosomal recessive conditions,
having one gene mutation does not usually cause
a health problem. You will only get symptoms of
the genetic condition if both of your genes have a
mutation.
It is these recessive gene mutations which may be
shared by consanguineous parents and can be
passed on to cause a genetic condition in the
children of some couples.
In societies with a tradition of first cousin
marriage, many couples are often more
closely related than first cousins are and
consequently their chance of having a child
with an autosomal recessive genetic
condition may be significantly higher.
GETTING CORRECT AND UP TO DATE
INFORMATION
It is important for couples who are blood relatives
and thinking about becoming parents, to seek
genetic counselling.
Some relationships are complex, involving a
number of generations where parents are closely
related. The specialised knowledge that the
genetic counselling team has is required to
estimate any possible impact on children resulting
from the couples family relationships.
In addition, a few genetic conditions are more
common in some population groups than in
others. If the ancestry of the parents is clear,
genetic testing may be possible to determine if
they are carriers of more common recessive
conditions.
For example, people where their background is
from:
Europe (including people from the United
Kingdom), have a 1 in 25 chance of being a
carrier of the faulty gene that causes cystic
fibrosis, a condition that affects the
respiratory and digestive system
People from Southern Europe, the Indian subcontinent, the Middle East, Africa and Asian
countries have a similar chance of being a
carrier of the faulty gene that causes one of
the forms of thalassaemia, a condition that
affects the blood.
For information about where genetic counselling
services are available in Australia, see
www.genetics.edu.au
www.genetics.edu.au
Page 3 of 3
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Updated 15 June2016
Department of Human Genetics
Division of Medical Genetics
www.genetics.emory.edu
Reproductive Options for Carriers of
Genetic Diseases & Chromosome Rearrangements
©2008 All rights reserved.
Individuals who are carriers for genetic diseases, such as sickle cell disease or cystic fibrosis, are at
increased risk to have a child with a genetic disease. Likewise, individuals who carry a balanced
chromosome rearrangement are at increased risk for miscarriage or having a child with birth defects
or mental retardation. There are several reproductive options available to couples who wish to have
children but are at increased risk for the above-mentioned concerns.
Natural Conception: Couples in which both are carriers of a genetic disease or one is a
balanced translocation carrier may consider a natural conception. With this option, no testing
is employed before conception and the couple may either pursue prenatal diagnosis or no
testing during the pregnancy. If no testing is performed during the pregnancy, a couple can
elect to test a baby at birth (if desired) to determine if he/she has a genetic disease or
chromosome abnormality.
Prenatal Diagnosis: Prenatal diagnosis is available during a pregnancy to diagnose a
chromosome abnormality or certain genetic diseases prior to birth. There are two routinely
used options for prenatal diagnosis:
1. Chorionic villus sampling (CVS) is routinely performed between 10-12 weeks of
pregnancy.
2. Amniocentesis is routinely performed after 15 weeks of pregnancy.
The complication rate, including miscarriage, associated with either procedure is
approximately 0.5% (1 in 200). Contact your doctor or genetic counselor for more specific
information regarding prenatal diagnostic options.
If prenatal testing reveals that the pregnancy is affected, the parents have the opportunity
to prepare to have a child with special needs, to arrange for adoption of a child with special
needs and/or to have the option of terminating the pregnancy. In the state of Georgia, the
legal limit for pregnancy termination is 24 weeks gestational age.
Preimplantation Genetic Diagnosis (PGD): PGD is accomplished by combining in vitro
fertilization (IVF) and genetic analysis to test an embryo prior to implantation. The eggs are
fertilized in the laboratory, one cell is removed from each embryo, and then genetic testing is
performed. Only unaffected embryos are transferred into the uterus for implantation. PGD is
available for many chromosome rearrangements but only a few genetic diseases. You can
discuss the costs and logistics of this option in more detail with a reproductive
endocrinologist. Contact your genetic counselor or a center which deals with assisted
reproduction to find out more about the availability of PGD for specific conditions.
Gamete (egg or sperm) Donation: A couple may choose to use a known or anonymous
egg or sperm donor. We recommend appropriate genetic testing and screening for any
gamete donor.
Adoption: There are many private and government adoption agencies available.
FS_048.2_2008
European Journal of Obstetrics & Gynecology and Reproductive Biology 232 (2019) 8796
Contents lists available at ScienceDirect
European Journal of Obstetrics & Gynecology and
Reproductive Biology
journal homepage: www.elsevier.com/locate/ejogrb
Review article
A review of the reproductive consequences of consanguinity
Oniya Olubunmia,* , Karen Nevesb , Ahmed Badreldeenc , Justin C. Konjea
a
Department of Obstetrics and Gynaecology, Sidra Medical and Research Center, PO Box 26999, Doha, Qatar
Sidra Medical and Research Center, PO Box 26999, Doha, Qatar
c
Feto Maternal Centre, 380 Al Markhiya St. P.O. Box 34181, Doha, Qatar
b
A R T I C L E I N F O
A B S T R A C T
Article history:
Received 25 June 2018
Received in revised form 15 October 2018
Accepted 22 October 2018
Background: Consanguinity is the close union, sexual relationship or marriage between persons who have
common biological ancestors usually up to about 2nd cousins. Contrary to general opinion consanguinity
is quite common and is practiced worldwide. It is an important topic as while rates of consanguineous
unions in certain society have decreased over time, rates have remained stable or increased in other
societies with rates as high as 80.6% in some communities. Our aim was to conduct a review looking at
general aspects of consanguinity and any published reproductive outcomes in literature. We also looked
at possible future directions that could be relevant in the management of the consanguineous couple to
help improve reproductive outcomes.
Method: We conducted a PUBMED, CINAHL, Web of Knowledge and Google Scholar search looking at
articles on consanguinity. Consanguinity articles related to pregnancy and reproduction were searched
using additional ?lters looking at our speci?c areas of interest. All relevant publications up to March 2015
were reviewed. Additional search for relevant articles pertaining to pre implantation genetic diagnosis
for future directions in the management of the consanguineous couple was done. Most publications were
found in books, on line articles and journals. Most were retrospective, population or cohort studies.
Result: Consanguinity is practiced by up to 10% of the worlds population with rates ranging from 80.6% in
certain provinces in the Middle East to less than 1% in western societies. It predates Islam and has been
practiced since Old Testament times. The most commonly cited reason for consanguinity is sociocultural
and socioeconomic although it is also more common in certain religions. In areas where rates of
Consanguinity are reducing urban migration and increasing education rates are thought to be
contributory.
Congenital malformations have long been established to be higher in consanguineous couples above the
background rate (4.5% Vs 1%).Due to Founder effect or a common ancestor, Consanguinity is most
commonly associated with Inborn errors of metabolism most of which are autosomal recessive.
Consanguinity increases the incidence of multifactorial disorders such as diabetes, cardiovascular
disorders, obesity and certain types of cancers. These may in turn affect reproductive outcomes. It may
also affect fertility rates. Pregnancy outcomes like increased pregnancy wastages and preterm labor have
been reported with consanguinity. Other studies produced con?icting evidence on its effect regarding
outcomes like hypertensive disorders of pregnancy and Intrauterine growth restriction.
Conclusion: Consanguinity continues to be practiced worldwide and in some countries rates are
increasing. The main reason for the practice appears to be sociocultural and socioeconomic although
religious beliefs is a contributory factor. The most signi?cant effects on reproductive outcomes are mostly
due to autosomal recessive inherited conditions and inborn errors of metabolism. It also signi?cantly
increases the inheritance of certain multifactorial disorders like diabetes which may indirectly affect
reproductive outcomes. In the future with the completion of the study of the whole human Genome and
current advances in Pre implantation Genetic diagnosis and screening it may be possible to mitigate some
of the adverse reproductive outcomes associated with consanguinity.
© 2018 Published by Elsevier B.V.
Keywords:
Consanguinity
Incidence
Prevalence and trends of consanguinity
Consanguinity worldwide
Consanguineous marriages
Determinants of consanguinity
Consanguinity trends
Consanguinity and pregnancy
Consanguinity and health effects
Consanguinity and fertility
Consanguinity and reproduction
Consanguinity and genetic disorders
Consanguinity and congenital
malformations
Consanguinity and co morbidity
Consanguinity and genetic counselling
Consanguinity and early pregnancy
Pre implantation genetic testing
Pre implantation genetic diagnosis
* Corresponding author.
E-mail addresses: ooniya@sidra.org, bunmi_oniya@yahoo.co.uk (O. Oniya), kneves@sidra.org (K. Neves), profbadreldeen@hotmail.com (B. Ahmed), jkonje@sidra.org
(J.C. Konje).
https://doi.org/10.1016/j.ejogrb.2018.10.042
0301-2115/© 2018 Published by Elsevier B.V.
88
O. Oniya et al. / European Journal of Obstetrics & Gynecology and Reproductive Biology 232 (2019) 87 96
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . .
De?nition . . . . . . . . . . . . . . . . . . . . . . . . . .
Incidence . . . . . . . . . . . . . . . . . . . . . . . . . .
Types . . . . . . . . . . . . . . . . . . . . . . . . . .
Predisposing factors . . . . . . . . . . . . . .
Perpetuating factors . . . . . . . . . . . . . .
Factors contributing to reducing rates
Reproductive consequences . . . . . . . .
Medical disorders . . . . . . . . . . . . .
Fertility . . . . . . . . . . . . . . . . . . . . .
Psychosexual . . . . . . . . . . . . . . . .
Pregnancy loss or wastage . . . . . .
Pregnancy complications . . . . . . .
Congenital malformations . . . . . .
Genetic . . . . . . . . . . . . . . . . . . . . . . . . .
Future directions . . . . . . . . . . . . . . . . .
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . .
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Introduction
Consanguinity is important because of its possible effects
on reproductive outcomes. It is a fascinating and often
debated subject not in the least because of the salacious
interest and moral stance sometimes adopted towards it
by cultures that do not practice consanguinity. Charles
Darwin in the mid-19th century in England was one of the
?rst scienti?cally minded writers to examine the issue of
consanguinity and explore some of the reproductive consequences. At the time Charles himself was married to his ?rst
cousin [1].
There are cultural, social and clinical implications for couples in
such unions. Due to the sharing of common alleles, it may lead to
several reproductive consequences both in the mother and the
offspring. This in turn may have a deleterious effect on reproduction, the family and society as a whole.
This review examines currently available evidence on general
aspects of consanguinity with emphasis on reproductive consequences.
De?nition
The dictionary de?nition of Consanguinity dates from around
the 14th century BC, however, the practice itself has been known
since biblical times. Consanguinity is derived from the French word
consanguinité and from the Latin word consanguinitatem
meaning of the same blood,” or being descended from the same
ancestor as another person [2].
The modern day de?nition of Consanguinity is close union,
sexual relations or marriage between persons who have common
biological ancestors usually up to 2nd cousins. This de?nition of
the degree of relatedness between couples has been chosen
because the genetic in?uence in marriages between couples
related to a lesser degree would be expected to differ only slightly
from that observed in the general population [3].
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