Triploidy

What is triploidy?

Triploidy is a rare condition where a cell has 69 total chromosomes instead of 46. This genetic abnormality affects fetuses and is life-threatening. The condition causes several congenital growth abnormalities and usually leads to a miscarriage or early infant death.

How many chromosomes do humans have?

During conception when the egg and sperm meet, each of your biological parents gives you 23 chromosomes, which equal one set. Each set contains 22 numbered chromosomes (autosomes) and one sex chromosome (X or Y). Your biological chromosomes pair up to equal 46 total chromosomes.

Any number of chromosomes above or below 46 is a chromosome abnormality that causes a chromosomal condition.

How common is triploidy?

Triploidy is rare and affects 1% to 3% of all pregnancies in the United States, which accounts for an estimated 30,000 to 200,000 pregnancies. Over 66% of all triploidy cases affect male fetuses.

What are the symptoms of triploidy?

A fetus diagnosed with triploidy will experience symptoms that affect their development in the uterus and could include:

• Congenital heart conditions.
• Abnormal brain development that causes seizures, developmental delay.
• Cystic kidney disease.
• Growth abnormalities of the intestines, spinal cord, liver and gallbladder.
• Fused fingers and toes.
• Short stature.
• Facial characteristics like wide-spaced eyes, cleft lip or palate, low-set ears and a low nasal bridge.
• Intellectual disability.
• Seizures.

Symptoms of triploidy also affect the pregnant parent and cause symptoms of preeclampsia, which could include:

• The placenta is full of cysts.
• High blood pressure.
• Swelling (edema).
• Excess albumin (protein) in your urine (albuminuria).

What causes triploidy?

An extra set of chromosomes in your developing fetus’ cells causes triploidy. Normally, your cells have 46 total chromosomes. Infants with triploidy have 69 total chromosomes. The extra set of chromosomes happens when:

• The egg is fertilized by two sperm.
• The egg is fertilized by a sperm that has an extra set of chromosomes.
• The sperm fertilizes an egg with an extra set of chromosomes.

This condition isn’t the result of something that the biological parents did before or during pregnancy. Triploidy usually happens sporadically or randomly and doesn’t have any association with a family history or the age of the birthing parent.

How is triploidy diagnosed?

Typically, your provider will diagnose triploidy in the developing fetus early in your pregnancy. They will look for symptoms of the condition that affect both the pregnant parent and the developing fetus, like high blood pressure in the parent or growth abnormalities in the developing fetus. Tests to confirm a diagnosis include:

• An ultrasound: An ultrasound is an imaging test that allows your provider to look at the fetus in your uterus. An ultrasound helps your provider look for congenital growth abnormalities and symptoms of the condition.
• Amniocentesis: Your provider will remove a small sample of your amniotic fluid to examine it for chromosome abnormalities.
• Chorionic villus sampling: Your provider will remove a small sample of your placenta with a needle to examine it for chromosome abnormalities.

Many pregnancies end early due to miscarriage. A miscarriage can lead to a triploidy diagnosis before pregnancy imaging and sampling tests occur.

If your baby is born, your provider can diagnose triploidy after performing a genetic test, which is a test that uses a small sample of your baby’s blood to detect changes to their chromosomes.

How is triploidy treated?

Most cases of triploidy end in miscarriage or an early loss of a newborn. Treatment is supportive for parents and caretakers, like talking with a mental health professional or counselor to help them grieve or cope with an unexpected loss.

If your baby is born, treatment focuses on reducing your baby’s life-threatening symptoms. This could include surgeries or medications to correct congenital growth abnormalities or supportive care to help them live comfortably.

How can I prevent triploidy?

You can’t prevent triploidy since the condition is the result of random, unexpected changes to your developing fetus’ DNA. You can’t plan for a triploidy pregnancy. Things you do before or during a pregnancy or how old you are aren’t factors for who this condition affects.

What can I expect if I have triploidy?

Most triploidy pregnancies end in a miscarriage, so it’s important to prepare yourself and your family for the potential loss of the fetus. This can be extremely difficult and painful. Some people find support through bereavement counseling or talking with a mental health specialist.

Babies who survive pregnancy may experience several complications as a result of congenital growth abnormalities. They may need adaptive devices like hearing aids, multiple surgeries throughout their life or long-term medication to prevent or reduce symptoms.

Children who do survive past infancy have a type of triploidy called mosaicism. Mosaicism is a condition where only some of your child’s cells have more chromosomes than expected (69 chromosomes) and other cells have the expected number of chromosomes (46 chromosomes). This change to the number of chromosomes in each of your child’s cells reduces the number and severity of growth abnormalities that they could have. The most severe and life-threatening cases of triploidy affect the chromosomes in all cells (complete triploidy) of a developing fetus.

What is the survival rate of a person diagnosed with triploidy?

Most triploidy pregnancies end early due to a miscarriage because the symptoms prevent the fetus from developing in your uterus. If your baby can be born, their chance of survival is dependent on the severity of their symptoms. Most infants pass away a few days after birth. It’s possible that your baby can survive into adulthood, but only a few cases exist in medical literature. Your baby will need extensive supportive care throughout their life to reduce life-threatening symptoms.

When should I see my healthcare provider?

Visit your healthcare provider or go to the emergency room if you experience symptoms of a miscarriage. These symptoms could include:

• Light to heavy bleeding.
• Cramps.
• Abdominal pain.
• Aches in your lower back.

What questions should I ask my doctor?

• Can I have another child if I have a miscarriage?
• Are there risks to the tests to diagnose triploidy?
• How should I take care of myself to prevent a miscarriage?
• Should I speak with a mental health professional to help me navigate my grief?

What is the difference between trisomy and triploidy?

Trisomy and triploidy are both genetic conditions that affect how many chromosomes you have. Trisomy is a condition where you have an extra copy of one chromosome. Triploidy is a condition where you have an extra set of chromosomes. You typically have 46 chromosomes. A person diagnosed with trisomy has 47 chromosomes. A person diagnosed with triploidy has 69 chromosomes.

A note from Cleveland Clinic

Triploidy is a life-threatening condition that can have a serious emotional impact on you and your family. If you learn that your developing fetus has triploidy, understand that this is a rare condition that you couldn’t prevent. Many people find support by talking with a mental health professional. A therapist can help you and your family navigate grief and the unexpected loss.