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What is Trisomy?: Trisomy: Types of Trisomy Disorders
Written by Medicover Team and Medically Reviewed by Dr K Sindhura , Neonatologist
Trisomy is a genetic condition in which an individual has three copies of a particular chromosome instead of the usual two. Humans normally have 46 chromosomes, arranged in 23 pairs, with one chromosome from each parent in every pair. In trisomy, the extra chromosome brings the total count to 47, which can disrupt normal development and function.
Trisomy can affect any chromosome and may result in mild to severe developmental, intellectual, or physical disabilities. Some trisomy types can lead to miscarriage early in pregnancy, while others result in live births with lifelong medical and developmental challenges.
What Are the Common Causes of Trisomy?
Trisomy occurs due to errors during cell division, specifically during meiosis, the process that creates reproductive cells (sperm and eggs). Instead of evenly dividing, a chromosome may fail to separate properly, resulting in a cell with an extra chromosome.
This is a random genetic event, not caused by anything a parent did or didn't do during pregnancy. However, the risk increases with maternal age, especially for pregnancies after age 35.
Chromosomal Nondisjunction
The primary cause of trisomy is a phenomenon known as nondisjunction. During meiosis, which is the process of cell division that produces gametes (sperm and egg cells), chromosomes may not separate properly. This results in gametes with an abnormal number of chromosomes, which, when fertilized, lead to trisomic offspring.
Maternal Age
Advanced maternal age is a significant risk factor for trisomy. Women over the age of 35 have a higher likelihood of producing eggs with chromosomal abnormalities. This correlation is due to the ageing of oocytes, which increases the risk of errors during cell division.
Genetic Predisposition
In some cases, trisomy can be attributed to genetic predispositions. Families with a history of chromosomal abnormalities may have a higher risk of producing offspring with trisomy. However, these cases are relatively rare.
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Get Second OpinionWhat Are the Different Types of Trisomy Disorders?
The specific trisomy disorder depends on which chromosome has the extra copy. Common types include:
Trisomy 21 (Down Syndrome)
- The most common trisomy.
- Causes developmental delays, intellectual disability, and distinct facial features.
- Many individuals live into adulthood with support.
Trisomy 18 (Edwards Syndrome)
- It is often linked to serious developmental delays and problems with the function or structure of internal organs.
- Many pregnancies result in miscarriage; few babies survive beyond the first year.
Trisomy 13 (Patau Syndrome)
- Often results in significant brain, heart, and organ defects.
- Low survival rates due to the severity of congenital anomalies.
Sex Chromosome Trisomies
These involve abnormalities in the sex chromosomes (X or Y):
- Trisomy X (XXX): Often subtle symptoms; may include tall stature and learning difficulties in females.
- Klinefelter Syndrome (XXY): Affects males; may cause infertility, low testosterone, and learning challenges.
- Jacob's Syndrome (XYY): Males may be taller with minor behavioral or developmental differences.
What are the Trisomy Symptoms and Warning Signs?
The symptoms of trisomy vary depending on the specific type of trisomy and the individual affected. Common symptoms across different types of trisomy include:
During Pregnancy
Prenatal signs of trisomy can include:
- Too much amniotic fluid (polyhydramnios)
- A small or underdeveloped placenta
- Less fetal movement than expected
- A single umbilical artery
- Structural abnormalities detected on ultrasound (e.g., cleft palate, heart defects)
After Birth
Symptoms vary by type but may include:
- Distinctive facial features (e.g., flat face, slanted eyes)
- Small stature or low birth weight
- Congenital defects (e.g., heart, kidney, brain)
- Feeding or breathing difficulties
- Developmental and intellectual delays
How is Trisomy diagnosed?
Genetic testing can lead to a trisomy diagnosis early in pregnancy. Diagnosis is confirmed at birth after a physical examination and further genetic chromosome testing on the baby through a blood sample.
What tests diagnose trisomy conditions?
During pregnancy, your healthcare provider may recommend screening tests that include a blood sample from the mother along with an ultrasound. The ultrasound helps detect signs that may suggest trisomy, such as increased amniotic fluid, nuchal translucency (fluid buildup at the back of the baby's neck), and abnormal limb lengths. These findings can indicate a possible genetic condition.
If screening results suggest a risk, additional diagnostic tests are used to confirm the diagnosis, including:
- Chorionic Villus Sampling (CVS): Between weeks 10 and 13 of pregnancy, your doctor may take a tiny sample of tissue from the placenta to check for genetic problems and find out the baby's sex.
- Amniocentesis: Between weeks 15 and 20, your doctor might take a small amount of the fluid around your baby (amniotic fluid) to test for possible health issues.
- Percutaneous Umbilical Blood Sampling (PUBS): This test involves taking a small blood sample from the baby's umbilical cord to look for health problems.
- Noninvasive Prenatal Testing (NIPT): After 10 weeks, your doctor can use a simple blood test from you to see if your baby might have any genetic conditions.
Once your baby is born, trisomy can be confirmed through:
- Physical examination: Your healthcare provider will look for physical signs and developmental differences that may suggest trisomy.
- Genetic testing: A blood sample is taken from your baby to check for extra chromosomes through karyotyping or chromosomal microarray analysis.
What Are the Treatment Options for Trisomy?
There is no cure for trisomy, but supportive treatments help manage symptoms and improve quality of life. Treatment plans vary depending on the type and severity of the condition.
Treatment may include
- Surgery to correct physical defects (e.g., cleft palate, heart issues)
- Early intervention therapies (speech, physical, occupational)
- Medications for seizures, infections, or other medical conditions
- Educational support and individualized learning plans
Multidisciplinary care from pediatricians, geneticists, therapists, and educators is often needed.
When to See a Doctor for Trisomy?
Trisomy refers to a genetic condition where a person has an extra chromosome, leading to health and developmental challenges. The most well-known types are Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome), and Trisomy 13 (Patau syndrome).
You should consult a doctor if:
- A prenatal screening test shows a higher risk of chromosomal abnormalities
- Your baby has unusual features seen in an ultrasound (such as heart defects or growth delays)
- After birth, your baby shows:
- Low muscle tone
- Delayed development
- Unusual facial features
- Feeding or breathing difficulties
- Congenital heart defects
Genetic testing and counseling may be recommended:
- During pregnancy (via blood tests, amniocentesis, or chorionic villus sampling)
- After birth, if the baby shows signs of a trisomy disorder
Early diagnosis is important for:
- Planning treatment and therapies
- Understanding the child's specific needs
- Providing emotional and medical support for families
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What Precautions Can Help Prevent Trisomy?
You cannot prevent trisomy, as it usually occurs by chance. However, certain steps can help assess and manage risk:
To reduce or understand your risk
- Consider genetic counseling before or during pregnancy
- Opt for prenatal genetic screening if you are over 35 or have a family history
- Maintain a healthy lifestyle before and during pregnancy
- Avoid alcohol, tobacco, and drugs during pregnancy
Living with Trisomy: What to Expect
Children with trisomy may face developmental and health challenges, but early detection and intervention greatly improve outcomes.
- Trisomy 21 (Down syndrome): With the right support, many individuals live full, active lives and may attend school and even work.
- Trisomy 13 and 18: These often lead to life-threatening complications early in life. Some children may survive longer with medical support, though developmental issues are typically profound.
Our Experience Treating Trisomy Conditions
At Medicover, we understand that learning your child has a trisomy condition can feel overwhelming. Whether it's Down syndrome, Edwards syndrome, or Patau syndrome, our care team is here with gentle guidance and expert care.
We offer:
- Advanced genetic testing and prenatal diagnostics
- Personalized care plans for your child's physical and developmental needs
- Support from pediatric specialists, therapists, and genetic counselors
- Help with navigating treatment options, therapies, and family support
We care for each child as an individual, with dignity, respect, and compassion. At Medicover, our goal is to help your child live the healthiest and happiest life possible while supporting you every step of the way.
