I'm a Carrier for a Genetic Condition, Do I Need Donor Eggs?

When building a family, intended parents wish to give their children the best possible start in life. However, for some individuals or couples, certain genetic conditions may increase the risk of passing on inherited disorders to their offspring. 

If you've recently discovered that you're a carrier for a genetic condition, you might be wondering about your options for building a healthy family. One question that I often get is whether using donor eggs is necessary. In this article, we will take a look at the most common genetic conditions that often lead families to donor egg in vitro fertilization (IVF). We aim to provide clarity on this topic, helping you understand your choices and the factors to consider. 

Understanding the impact of genetic conditions

Genetic conditions are inherited through the passing of genes from parents to their children. Each person has two copies of every gene, one inherited from the mother and one from the father. The way in which a genetic condition is inherited depends on the specific pattern of inheritance for that condition. 

• Autosomal dominant disorders, such as Huntington's disease, only require one copy of the mutated gene to cause the condition, meaning if one parent has the mutation, there is a 50% chance of passing it on to the child. 
• Autosomal recessive disorders, like cystic fibrosis and sickle cell anemia, require both copies of the gene to be mutated for the condition to manifest. If both parents are carriers of the recessive gene mutation, there is a 25% chance their child will have the condition. 
• X-linked recessive disorders, such as Duchenne muscular dystrophy, are caused by mutations in genes located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. As a result, X-linked recessive conditions primarily affect males. Female carriers have a 50% chance of passing the mutation on to their children, with sons having a 50% chance of being affected and daughters having a 50% chance of being carriers.
• X-linked dominant disorders, such as Rett syndrome, can affect both males and females. However, they often result in more severe symptoms in males. If a mother carries the gene, she has a 50% chance of passing it to each child. If a father carries the gene, all his daughters will inherit it, but none of his sons will.
• Mitochondrial disorders are unique because they are inherited only from the mother. An estimated 1 in 5,000 people has a genetic mitochondrial disease. Mitochondria, the energy-producing structures in our cells, contain their own DNA. All mitochondria in a fertilized egg come from the mother's egg cell, not the father's sperm. Therefore, mitochondrial genetic disorders are passed from mother to all her children, but only daughters will pass it on to the next generation.

While having a genetic mutation increases the risk of developing a condition, it does not always guarantee that the condition will manifest, as other genetic and environmental factors can also play a role. This means you or your partner could be a silent carrier of a condition that may show up in your child’s genes. Because of this, the American College of Obstetricians and Gynecologists (ACOG) recommends that people considering pregnancy get carrier screenings before conception.

Cystic Fibrosis (CF)

Cystic Fibrosis (CF) is an inherited disorder that affects the lungs, digestive system, and other organs. It causes thick, sticky mucus to build up in the lungs, leading to persistent lung infections and difficulty breathing. CF also disrupts the function of the pancreas, preventing proper digestion. The severity of CF varies, but it is a progressive condition that often leads to shortened life expectancy. In the United States, approximately 1 in every 3,000 to 4,000 newborns is diagnosed with CF, and about 1 in 25 people are carriers of the CF gene mutation.

If both partners are carriers of the CF gene mutation, there is a 25% chance their child will have CF, and 50% chance the child will be a carrier but will not have CF.

Huntington's Disease (HD)

Huntington's Disease (HD) is a progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability. Symptoms usually begin between the ages of 30 and 50 and worsen over time, leading to complete dependence on others for care. HD is rare, affecting about 1 in every 10,000 to 20,000 people. There is currently no cure for HD, and it is ultimately fatal.

HD is an autosomal dominant disorder, meaning if one parent has the HD gene mutation, there is a 50% chance of passing it on to the child. 

Fragile X Syndrome (FXS)

Fragile X Syndrome (FXS) is an inherited condition that causes intellectual disability, behavioral and learning challenges, and various physical characteristics. It is caused by a mutation in the FMR1 gene on the X chromosome. Males with Fragile X Syndrome are usually more severely affected than females. Fragile X Syndrome is the most common inherited cause of intellectual disability, affecting approximately 1 in 4,000 males and 1 in 8,000 females.

If the mother is a carrier of the Fragile X premutation or full mutation, she has up to a 50% chance of passing it on to her children. Fragile X is also associated with premature ovarian failure.

Sickle Cell Anemia 

Sickle Cell Anemia is a group of inherited red blood cell disorders. In this condition, red blood cells become crescent or "sickle" shaped, which can cause them to get stuck in small blood vessels, blocking blood flow and oxygen to various parts of the body. This leads to pain, organ damage, and an increased risk of infections. In the United States, sickle cell anemia affects approximately 1 in every 365 Black or African-American births and 1 in every 16,300 Hispanic-American births.

If both partners are carriers of the sickle cell trait, there is a 25% chance their child will have sickle cell anemia because it is an autosomal recessive disorder. 

Tay-Sachs Disease

Tay-Sachs Disease is a rare inherited disorder that progressively destroys nerve cells in the brain and spinal cord. Babies with Tay-Sachs disease appear normal at birth but start showing symptoms around 3 to 6 months of age, including weakness, loss of motor skills, and seizures. The condition progressively worsens, leading to blindness, paralysis, and death, usually by the age of 4 or 5. Tay-Sachs disease is rare, occurring in about 1 in every 320,000 live births, but it is more common among certain populations, such as Ashkenazi Jews.

If both partners are carriers of the Tay-Sachs gene mutation, there is a 25% chance their child will have Tay-Sachs disease. 

Duchenne Muscular Dystrophy (DMD) 

Duchenne Muscular Dystrophy (DMD) is an X-linked recessive disorder characterized by progressive muscle weakness and degeneration. DMD primarily affects boys, with symptoms usually beginning between the ages of 2 and 4. The condition progressively worsens, leading to difficulty walking, breathing, and performing daily activities. DMD affects approximately 1 in every 3,500 to 5,000 male births worldwide, and there is currently no therapy or cure.

As DMD is caused by a mutation in a gene on the X chromosome, female carriers have a 50% chance of passing it on to their children. Sons of female carriers have a 50% chance of inheriting DMD, while daughters have a 50% chance of being carriers. 

Family-building options for carriers of genetic conditions

1. Unassisted conception with prenatal testing

Some families choose to conceive unassisted and use prenatal testing to check for some conditions during pregnancy.  These tests can provide information about whether the fetus has inherited the genetic condition. However, some diagnostic tests may have some risks for your baby so you’ll want to talk to your OBGYN about these risks.

2. IVF with PGT-M

IVF with preimplantation genetic diagnosis (PGT-M, formerly known as PGD) allows embryos to be screened for specific genetic defects involving a single gene, like cystic fibrosis, before implantation. This can significantly reduce the risk of passing on the condition. However, PGT doesn't test for all possible genetic issues.

Although it would require undergoing IVF, if you fall into any of the below categories, conducting PGT-M testing could help you get closer to having a baby that is not a carrier of that particular genetic condition or chromosomal abnormality you’re trying to screen for.

If any of these apply to you and your partner, it might be worth chatting with your doctor about PGT-M testing:

• You are a carrier of an X-linked condition
• You and your partner both carry the same autosomal recessive condition (like Cystic Fibrosis)
• You or your partner have an autosomal dominant condition
• You or your partner have a mutation associated with a hereditary cancer
• You already had a pregnancy (or child) with a single gene disorder

3. IVF with donor eggs

Opting for donor eggs can eliminate the risk of passing on your genetic condition. This choice ensures that the genetic material from the egg doesn't carry your specific mutation. 

4. Adoption

Some carriers choose to build their families through adoption, avoiding genetic concerns altogether while providing a loving home to a child in need.

When to consider egg donation

The need for donor eggs isn't automatic just because you're a genetic carrier. Several factors come into play:

• Your partner's genetic status: If your partner isn't a carrier for the same condition, your risk of having an affected child may be low depending on the genetic condition.
• The specific genetic condition: Some conditions have a higher risk of transmission or more severe health implications than others.
• Your personal risk tolerance: Some families are comfortable with a small risk, while others prefer to eliminate risk entirely.
• Family planning goals: The number of children you hope to have may also influence your decision.

For individuals or couples facing the challenges of genetic conditions, using an egg donor can provide a means to build your family while reducing the risk of passing on inherited disorders. Egg donors undergo thorough medical and genetic screening to ensure they are healthy and do not carry known genetic mutations.

Anyone considering egg donation should consult with a genetic counselor to discuss their specific genetic risks and potential options. These professionals can help you navigate the complexities of genetic testing, donor matching, and the medical aspects of the egg donation process. If you work with Cofertility, we can help recommend an experienced genetic counselor. 

Using an egg donor can significantly reduce the risk of passing on certain genetic conditions, but it is not a guarantee of a healthy child. All pregnancies carry some inherent risks, and factors such as the health of the gestational carrier and environmental influences can also impact the child.

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Read more:

• Genetic Carrier Screening During and Donor Egg IVF
• Nine Things To Know About Raising A Donor-Conceived Child
• 35 Questions to Ask Your Doctor About Using Donor Eggs
• I'm a Fertility Psychologist. Here's What I Want You to Know About Growing Your Family Through Egg Donation