Edwards Syndrome (Trisomy 18)

What is Edwards Syndrome (Trisomy 18)?

Edwards syndrome, also called trisomy 18, is a chromosomal condition that occurs when a baby has three copies of chromosome 18 instead of two. This extra genetic material affects how a baby's body and organs develop before birth. The condition causes serious physical and developmental challenges that begin in the womb.

Most cases of Edwards syndrome happen randomly during the formation of reproductive cells. The extra chromosome is not inherited from parents and is not caused by anything the mother or father did. Edwards syndrome affects about 1 in 5,000 live births. It is the second most common trisomy after Down syndrome, which involves chromosome 21.

Many pregnancies with Edwards syndrome end in miscarriage or stillbirth. Babies who are born with this condition often face life-threatening medical complications. Some infants survive only days or weeks after birth, while others may live for several months or, in rare cases, into early childhood. Each child's experience with Edwards syndrome is different, and families work closely with medical teams to provide comfort and care.

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Symptoms

Symptoms of Edwards syndrome usually appear during pregnancy or immediately after birth. Physical features and medical problems vary in severity from child to child.

Low birth weight and small size for gestational age
Small, abnormally shaped head
Clenched fists with overlapping fingers
Underdeveloped nails and short breastbone
Heart defects, often affecting the heart's chambers or valves
Kidney abnormalities
Feeding difficulties and poor weight gain
Breathing problems
Developmental delays and intellectual disability
Weak muscle tone or increased muscle tone

Nearly all babies with Edwards syndrome show multiple symptoms at birth. Many of these signs can be detected on ultrasound imaging during pregnancy.

Causes and risk factors

Edwards syndrome is caused by having an extra copy of chromosome 18. Most cases occur due to full trisomy 18, where every cell in the body has three copies of this chromosome. Less commonly, partial trisomy 18 occurs when only part of the extra chromosome is present. Mosaic trisomy 18 happens when only some cells have the extra chromosome while others are normal.

The extra chromosome usually results from a random error during cell division when egg or sperm cells form. This error is not caused by environmental factors or parental behavior. Maternal age is the primary risk factor. Women over age 35 have a higher chance of having a pregnancy affected by chromosomal conditions, including Edwards syndrome. However, most babies with trisomy 18 are born to younger mothers, simply because younger women have more babies overall. The condition is not typically inherited, and most families have only one affected pregnancy.

How it's diagnosed

Edwards syndrome is usually suspected during pregnancy through prenatal screening tests. First-trimester screening combines a blood test and ultrasound to assess risk. Second-trimester screening measures hormone levels in the mother's blood, including estriol, which may be reduced when Edwards syndrome is present. Cell-free DNA testing can detect the extra chromosome 18 with high accuracy. Ultrasound may reveal physical features associated with the condition, such as heart defects or growth delays.

Diagnostic testing provides a definitive answer. Amniocentesis involves taking a sample of amniotic fluid to examine the baby's chromosomes. Chorionic villus sampling tests placental tissue. After birth, doctors diagnose Edwards syndrome through a physical exam and a blood test called a karyotype, which shows the chromosome pattern. Talk to your doctor or a genetic counselor about screening and testing options during pregnancy. They can help you understand your results and what they mean for your family.

Treatment options

Treatment for Edwards syndrome focuses on comfort care and managing specific medical complications. Each child receives an individualized care plan based on their needs and the family's wishes.

Medical monitoring for heart defects, breathing problems, and feeding difficulties
Nutritional support through specialized feeding techniques or feeding tubes
Surgery to correct specific problems like heart defects, though this carries significant risk
Physical therapy and occupational therapy to support development
Hospice and palliative care to ensure comfort and quality of life
Genetic counseling for families to understand the condition and future pregnancy risks
Emotional and psychological support for parents and siblings

Families work closely with a team of specialists, including geneticists, cardiologists, and neonatologists. There is no cure for Edwards syndrome. Care decisions are deeply personal and should align with each family's values and goals for their child's life.

Frequently asked questions

Edwards syndrome, or trisomy 18, is a genetic condition where a baby has three copies of chromosome 18 instead of two. This extra genetic material causes serious developmental problems affecting many organs and body systems. The condition is present from conception and affects physical and intellectual development.

Edwards syndrome affects about 1 in 5,000 live births. It is more common in pregnancy, but many affected pregnancies end in miscarriage or stillbirth. Edwards syndrome is the second most common trisomy condition after Down syndrome. Maternal age over 35 increases the risk, but most cases occur in younger mothers who have more babies overall.

Yes, Edwards syndrome can often be detected through prenatal screening and diagnostic tests. Screening tests like blood work and ultrasound assess risk, while diagnostic tests like amniocentesis provide definitive results. Cell-free DNA testing can detect trisomy 18 with high accuracy. Many physical features of Edwards syndrome can also be seen on prenatal ultrasound.

Life expectancy varies, but many babies with Edwards syndrome live only days or weeks after birth. About 50% of babies survive to 2 weeks of age, and 5 to 10% live beyond their first year. Some children with mosaic or partial trisomy 18 may live longer. Each child's medical complications and overall health influence survival.

Edwards syndrome is caused by a random error during cell division that creates an extra copy of chromosome 18. This error typically occurs when egg or sperm cells form. The condition is not caused by anything parents did or did not do during pregnancy. It is usually not inherited and occurs by chance.

Newborns with Edwards syndrome are often small with low birth weight. They typically have a small head, clenched fists with overlapping fingers, and feeding difficulties. Many babies have heart defects, kidney problems, and breathing issues. Physical features may include a small jaw, low-set ears, and an underdeveloped breastbone.

There is no cure for Edwards syndrome because it is a chromosomal condition present in every cell. Treatment focuses on managing symptoms and providing comfort care. Some medical interventions like surgery for heart defects may be considered, but these carry significant risk. Care plans are individualized based on each child's needs and family preferences.

Most cases of Edwards syndrome are not inherited and occur randomly. Full trisomy 18, the most common form, happens by chance during cell division. Very rarely, a parent may carry a balanced translocation involving chromosome 18, which can increase the risk of having another affected pregnancy. Genetic counseling can help assess individual family risk.

Both are trisomy conditions involving an extra chromosome, but they affect different chromosomes. Down syndrome involves chromosome 21, while Edwards syndrome involves chromosome 18. Edwards syndrome is generally more severe, with lower survival rates and more serious medical complications. Down syndrome is much more common and most individuals live into adulthood with appropriate support.

Families can access genetic counseling, palliative care teams, and support groups for parents who have lost a child. Many hospitals offer perinatal hospice programs for pregnancy support and planning. Online communities connect families facing similar experiences. Social workers and chaplains provide emotional support. These resources help families navigate difficult decisions and find comfort during challenging times.