Trisomy 18Edit

Trisomy 18, also known as Edwards syndrome, is a chromosomal condition caused by the presence of an extra copy of chromosome 18 in the body's cells. The vast majority of cases arise from full trisomy 18, where every cell carries three copies of chromosome 18, though mosaic trisomy 18 and trisomy due to a translocation also occur. The syndrome is among the more common autosomal trisomies and is associated with numerous congenital anomalies that affect the heart, brain, and other organs. Most pregnancies with trisomy 18 end before or shortly after birth, but a small fraction of affected individuals survive beyond infancy. Edwards syndrome.

Trisomy 18 is the result of chromosomal nondisjunction events during gamete formation, most often maternal meiosis I, leading to an extra chromosome in the embryo. Maternal age is a recognized risk factor, with higher maternal age correlating with increased likelihood of nondisjunction, though the condition can occur at any age. In addition to the more common full trisomy 18, a minority of cases are due to mosaicism (some cells carry three copies of chromosome 18 while others are normal) or to translocation events where part or all of chromosome 18 attaches to another chromosome. Most cases are not inherited unless a parent carries a balanced translocation involving chromosome 18, which can raise recurrence risk in future pregnancies. Nondisjunction, Mosaicism, Translocation (genetics), Meiosis, Karyotype.

Clinical features of trisomy 18 constitute a recognizable pattern that affects multiple organ systems. Characteristic craniofacial and limb findings include micrognathia (a small jaw), low-set ears, small mouth, clenched fists with overlapping fingers, and rocker-bottom feet. Many infants have severe congenital heart defects, such as ventricular septal defects or other complex malformations, which are a major determinant of prognosis. Growth restriction, brain, kidney, and gastrointestinal anomalies are also common. Because of the severe anomalies, feeding difficulties and respiratory problems are frequent in the newborn period. The phenotype is variable, especially in mosaic cases, where some features may be milder and survival longer. Congenital heart defect, Rocking-bottom feet, Prenatal diagnosis.

Diagnosis can occur prenatally or after birth. Prenatal screening and diagnostic pathways commonly begin with ultrasound findings such as growth restriction, brain anomalies, or heart defects, along with noninvasive prenatal testing (NIPT) that can indicate trisomy 18. A definitive prenatal diagnosis is made by invasive testing, typically chorionic villus sampling (CVS) or amniocentesis, followed by karyotyping or chromosomal microarray to confirm trisomy 18 and to determine whether mosaicism or a translocation is involved. After birth, a chromosomal analysis (karyotype) confirms the diagnosis. Noninvasive prenatal testing, Chorionic villus sampling, Amniocentesis, Karyotype.

Prognosis for trisomy 18 is highly variable and heavily dependent on the form of the condition. In full trisomy 18, most affected pregnancies do not result in long-term survival; among live births, a substantial majority die within the first month, and only a small percentage survive beyond the first year. Mosaic trisomy 18 can carry a wider range of outcomes, with some individuals living for months to years, though significant medical challenges remain common. Survivors beyond early infancy are rare and typically require multidisciplinary medical care. Because prognosis can be difficult to predict even in the same family, physicians emphasize individualized counseling and careful consideration of quality of life in care planning. Mosaicism, Life expectancy.

Management of trisomy 18 focuses on comfort, quality of life, and supportive care rather than a curative treatment, as there is no available cure for the syndrome. Neonatal and pediatric teams may address feeding support, respiratory care, and cardiac or other organ-specific management as appropriate, with decisions about the extent of life-sustaining interventions guided by the clinical status of the child and the preferences of the family. In many cases, families and clinicians engage in advance care planning and genetic counseling to understand prognosis, possible outcomes, and the risks and benefits of different treatment approaches. Pediatric palliative care, Genetic counseling.

Controversies and debates surrounding trisomy 18 reflect broader conversations about prenatal screening, medical decision-making, and disability. Proponents of robust parental autonomy argue that families should receive clear, compassionate information and be free to choose among available options, including continuing a pregnancy with contingent plans for care or choosing palliative pathways. Critics of broad screening or particular counseling practices worry that reflexive emphasis on prognosis or disability may pressure families toward termination and undervalue the lives of people with trisomy 18 or related conditions. Advocates in disability communities often emphasize the value of every life and caution against framing a disability as a lack of potential or happiness. Proponents of responsible resource stewardship argue that health systems should consider the costs and benefits of extensive neonatal interventions, particularly when prognosis is poor, while ensuring that decisions remain patient- and family-centered rather than policy-driven. In this context, the right-of-center perspective tends to foreground parental rights, informed consent, and the responsible use of resources, while acknowledging legitimate ethical complexities without reducing a life to a mere calculation. Critics may contend that disability-centered critiques sometimes obscure the autonomy of families and risk pressuring decisions; supporters respond that respectful dialogue and high-quality counseling help navigate these difficult choices. Genetic counseling, Prenatal testing, Healthcare costs, Pediatric ethics.

See also - Edwards syndrome - Down syndrome - Patau syndrome - Nondisjunction - Mosaicism - Translocation (genetics) - Prenatal diagnosis - Genetic counseling - Pediatric palliative care