Michael S. Porter
Eric C. Nordby
Learning that your child has been diagnosed with a serious genetic condition can feel overwhelming. Trisomy 18, also known as Edwards syndrome, is a chromosomal disorder that brings profound challenges and difficult questions for families. Understanding what Trisomy 18 means, how it affects development, and what care options exist can help you make informed decisions and find the support your family needs during this time.
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What is Trisomy 18?
Trisomy 18 is a severe genetic disorder caused by the presence of three copies of chromosome 18 in the body’s cells, rather than the usual two. This extra genetic material disrupts normal development and causes a wide range of physical and intellectual disabilities. Most babies with Trisomy 18 experience significant growth restriction, multiple organ malformations, and life-threatening complications.
The condition was first described by British geneticist John Edwards in 1960, which is why it is also called Edwards syndrome. It is the second most common autosomal trisomy after Down syndrome (trisomy 21), though it is much more severe.
How Trisomy 18 Happens
Trisomy 18 happens because of a random error during the formation of reproductive cells or in early embryonic development. This error, called nondisjunction, causes an egg or sperm cell to have an extra copy of chromosome 18. When fertilization occurs, the resulting embryo has three copies of the chromosome in every cell.
The condition is usually not inherited. It occurs spontaneously and is not caused by anything the parents did or did not do during pregnancy. However, the risk of having a baby with Trisomy 18 increases significantly with advanced maternal age, particularly for mothers over 35.
Most cases involve full trisomy, where every cell in the body carries the extra chromosome. Less commonly, mosaic trisomy 18 can occur, where only some cells have the extra chromosome. Babies with mosaic trisomy may have milder symptoms and better outcomes. Partial trisomy, where only part of chromosome 18 is duplicated, is also rare and may have variable effects depending on which portion is involved.
Signs and Symptoms of Trisomy 18
Babies with Trisomy 18 typically have severe growth restriction that begins before birth. Birth weight is usually low, and many physical features and internal organ problems are present from the start.
Physical features often include a small head (microcephaly), a prominent back of the head, a small jaw and mouth, and low-set, malformed ears. The face may have a distinctive appearance with short eye openings and a small, upturned nose.
Hand and foot abnormalities are common. Babies often hold their hands in tight fists with the index finger overlapping the third finger and the fifth finger overlapping the fourth. Fingernails may be underdeveloped. Feet may have a characteristic rocker-bottom shape, and clubfeet are frequently seen.
The chest is often narrow with a short breastbone. Many babies have hernias, either at the belly button (umbilical hernia) or in the groin (inguinal hernia).
Internal organ problems are serious and widespread. Heart defects occur in the majority of babies, including holes between the heart chambers (ventricular septal defect) and vessels that fail to close after birth (patent ductus arteriosus). Kidney malformations, intestinal problems, and abdominal wall defects can also be present.
Neurological and muscular issues are common. Many babies have low muscle tone (hypotonia) early on, which can later shift to increased muscle rigidity. About 30% of infants experience seizures. Feeding difficulties, a weak cry, and trouble breathing are frequent challenges.
How Trisomy 18 Is Diagnosed
Many cases of Trisomy 18 are identified before birth. During routine prenatal care, maternal blood screening tests may show patterns that suggest a chromosomal abnormality. Ultrasound examinations can detect signs such as severe growth restriction, heart defects, clenched hands, and other physical abnormalities. Some ultrasounds also reveal a single umbilical artery, which is more common in babies with Trisomy 18 than in the general population.
If screening tests suggest Trisomy 18, diagnostic testing can confirm the diagnosis. Amniocentesis (testing amniotic fluid) or chorionic villus sampling (testing placental tissue) can provide a definitive chromosomal analysis. These tests carry a small risk and are offered after careful counseling.
After birth, doctors may suspect Trisomy 18 based on the baby’s physical appearance and symptoms. A blood test called a karyotype confirms the diagnosis by showing the extra chromosome 18 in the baby’s cells.
How Common is Trisomy 18?
According to the Centers for Disease Control and Prevention, Trisomy 18 affects about 1 in 3,336 live births in the United States. However, this number reflects only babies born alive. Many pregnancies affected by Trisomy 18 result in miscarriage or stillbirth. When these losses are included, the overall occurrence is much higher.
Trisomy 18 affects both boys and girls, though more girls with the condition are born alive. This may be because female fetuses with Trisomy 18 are more likely to survive to birth than male fetuses.
Prognosis and Life Expectancy
Trisomy 18 is a life-limiting condition. Many babies do not survive pregnancy or are stillborn. Of those born alive, about 42% pass away within the first week of life. Approximately 88% do not survive past the first year. Around 10% live beyond their first birthday, though nearly all have profound disabilities and complex medical needs.
The severity of heart defects, kidney problems, and breathing difficulties largely determines survival. Babies with less severe malformations or mosaic trisomy may have longer survival, though predicting outcomes for individual children is difficult.
These statistics can be deeply painful to hear. Every family’s experience is unique, and some children do live longer than expected. What matters most is ensuring your child receives compassionate care and that your family gets the support you need.
Medical Care and Treatment Options
There is no cure for Trisomy 18. Medical care focuses on providing comfort, managing symptoms, and supporting quality of life. Decisions about the level and type of medical intervention are deeply personal and should be guided by your family’s values, your child’s specific condition, and discussions with your medical team.
Supportive care often includes help with feeding, as many babies cannot feed by mouth and may require tube feeding through the nose or directly into the stomach. Oxygen therapy can help with breathing difficulties. Medications may be used to control seizures or treat infections.
Some families and medical teams choose to pursue more aggressive interventions, including surgery to repair heart defects or correct gastrointestinal problems. Research shows that in carefully selected cases, surgical interventions can extend survival. However, surgery carries significant risks, and outcomes remain uncertain.
Children who survive infancy need ongoing care from multiple specialists, including pediatricians, cardiologists, lung specialists, gastroenterologists, and neurologists. Physical therapy, occupational therapy, and speech therapy can support development and comfort, though progress is often limited.
Palliative care is an important part of managing Trisomy 18. Palliative care teams focus on comfort, pain control, and supporting families through difficult decisions. This type of care can be provided alongside other treatments and does not mean giving up on your child. It means prioritizing your child’s comfort and your family’s needs.
Where to Find Specialized Care in New York
Several major medical centers in New York provide diagnostic services, neonatal intensive care, surgical intervention when appropriate, and family support for babies with Trisomy 18.
Mount Sinai Hospital in New York City has specialized programs in genetics, neonatology, and pediatric cardiology. Their teams offer diagnostic testing, treatment planning, and counseling for families facing complex genetic conditions.
NYU Langone Health provides comprehensive neonatal care, genetic counseling, and multidisciplinary support for babies with chromosomal disorders and their families.
NewYork-Presbyterian, including the campuses affiliated with Columbia University and Weill Cornell Medicine, offers advanced neonatal and cardiac care, as well as genetic services and palliative care programs.
Albany Medical Center serves families in upstate New York with neonatal intensive care, genetic testing, and coordinated specialty services.
The New York Center for Rare Diseases helps families navigate resources, connect with specialists, and access support services across the state.
Support for Families
Caring for a child with Trisomy 18, or losing a child to this condition, is one of the most difficult experiences a family can face. You should not have to navigate this alone.
Genetic counseling is an important resource. Genetic counselors can explain what Trisomy 18 means, discuss the likelihood of recurrence in future pregnancies (which is very low for full trisomy 18), and help you understand testing options. They also provide emotional support and connect you with other resources.
Support groups, both in person and online, allow families to share experiences, ask questions, and find comfort with others who truly understand. Many hospitals and nonprofit organizations facilitate these groups.
Practical support matters too. Social workers can help coordinate medical appointments, connect you with respite care, and guide you through insurance and financial assistance programs. Occupational therapists and speech therapists can improve your child’s comfort and ability to interact with you.
If your child’s condition is terminal, end-of-life planning services, including hospice care, can help ensure your child is comfortable and your family is supported through every step of the process.
Current Research and Evolving Approaches
Medical understanding of Trisomy 18 continues to evolve. Historically, aggressive medical interventions were rarely offered to babies with this diagnosis. However, some medical centers and families are now exploring whether certain treatments, particularly heart surgeries, can improve outcomes for selected patients.
Recent studies have documented cases of children with Trisomy 18 surviving into adolescence or even adulthood, though these cases remain uncommon and involve complex medical care. Research is ongoing into which factors predict longer survival and better quality of life.
Surveillance guidelines have been developed to monitor for complications that may arise over time. For example, children with Trisomy 18 have a slightly increased risk of developing Wilms tumor, a kidney cancer, so some specialists recommend periodic kidney screenings for survivors.
Current best practices emphasize shared decision-making between families and medical teams. Every child’s situation is different, and treatment plans should respect your family’s goals and priorities, with honest discussions about risks, benefits, and realistic expectations.
Moving Forward After a Trisomy 18 Diagnosis
If your child has been diagnosed with Trisomy 18, you are facing a journey that no parent should have to walk. The information and statistics can feel overwhelming and heartbreaking. But you are not alone. Medical teams, support organizations, and other families are here to help you.
Focus on what matters most to your family. Some families choose comfort care from the start. Others pursue medical interventions in the hope of extending their child’s life. There is no single right answer. What is right is what aligns with your values and what feels best for your child.
Hold your baby. Spend time together. Create memories. Accept help when it is offered. Give yourself permission to feel whatever emotions arise, whether that is grief, love, anger, hope, or all of them at once.
The road ahead may be short or longer than expected. It will certainly be difficult. But the love you have for your child, and the care you provide, matter deeply.