Trisomy Awareness

 Trisomy Awareness Month

Trisomy Awareness Month

March is Trisomy Awareness Month. What is trisomy? The chromosomes in our bodies make up the genetic blueprint of who we are. Most humans have 23 pairs of chromosomes, or 46 chromosomes in total. However, there is a chance that during the reproductive process the cells do not divide properly, resulting in an additional copy of a chromosome.  

When trisomy occurs, this random error in cell division results in an extra partial or full chromosome that attaches to another pair, creating a total of 47 chromosomes in that individual.  

There are multiple types of trisomy conditions, but the three most common are Trisomy 21, Trisomy 18, and Trisomy 13.  

Trisomy 21 

Trisomy 21, or Down Syndrome, results from an extra copy of chromosome 21. Down Syndrome is the most common chromosomal condition in the United States, affecting 1 in every 700 babies born each year.  

Patients with Down Syndrome display a wide range of symptoms including developmental and intellectual disabilities, congenital heart defects, certain facial features, and gastrointestinal abnormalities, among other things.  

Down Syndrome is a lifelong condition that requires management by multiple specialists. Services like physical, occupational, or speech therapy typically start early to maximize patients’ physical and intellectual potential. With recent advances in medical practice and overall improvement in care, life expectancy of individuals with Down Syndrome has risen to an average of 60 years.  

Trisomy 18 

Trisomy 18, also called Edwards Syndrome, is the second most common trisomy and results from an extra copy of chromosome 18. The live birth prevalence rate for Trisomy 18 is 1 in 8600 births. The overall prevalence of trisomy 18 has increased in the last two decades, likely due to a rise in maternal age during pregnancy.  

Clinical abnormalities of infants born with Edwards syndrome affect many body systems and causes of death include neurologic instability, cardiac failure, and respiratory failure. The median survival rate of babies born with Trisomy 18 ranges from 3 to 14.5 days and only 5 to 10% survive beyond the first year of life.  

Trisomy 13 

Trisomy 13, also called Patau syndrome, is the third most common trisomy and demonstrates the presence of an extra copy of chromosome 13. This trisomy occurs in approximately every 1 in 10,000 to 20,000 live births and has an antenatal mortality rate of over 95%. Most gestations with Trisomy 13 are terminated.  

The most common congenital anomalies found in liveborn infants with Trisomy 13 are related to the cardiac and nervous systems. They are typically considered incompatible with life.  

Only about 6-12% of babies with Trisomy 13 survive beyond their first year of life. 

Screening and diagnosis 

Most cases of trisomy are diagnosed prenatally. There are two types of tests that can detect trisomy during pregnancy: screening tests and diagnostic tests. Screening tests consist of maternal blood testing, ultrasound, or a combination of the two. Abnormal test results signify an elevated risk for fetal aneuploidy. However, these tests only screen for an increased risk of specific conditions like trisomy. Further diagnostic testing is needed to know if the fetus has a definite diagnosis.  

Chorionic villus sampling or amniocentesis are the two diagnostic tests indicated when initial screening suggests an elevated risk of fetal aneuploidy. These are performed at different points in the pregnancy and draw a small sample of cells from the placenta or amniotic fluid.  

Abnormalities found in the chromosomes of the collected cells reveal the diagnosis of the fetus.  

Related: Ethics and Moral Distress for Healthcare Professionals

A heartbreaking decision 

Parents face a difficult and emotional decision when presented with a prenatal diagnosis that is potentially lethal, life-limiting, or severely debilitating. Families may feel guilt, hopelessness, fear, anger, isolation, and more as they consider whether to continue or terminate a pregnancy.  

Healthcare professionals supporting these parents offer individualized discussions and provide an open and supportive environment throughout the decision-making process, allowing parents to explore all options and consider the factors that are most important to them.  

A multidisciplinary team, including genetic counselors, neonatologists, social workers, and primary obstetric providers, can help advise parents. Education involves the potential complications of both termination and continuation of the pregnancy. It also includes possible interventions available for postnatal care, including intensive interventions versus palliative care. 

Caring for infants diagnosed with trisomy 

Since the 1980s, care has changed considerably for infants diagnosed with trisomy. For example, it is no longer acceptable to withhold life-saving treatment for infants with Down Syndrome that lack the presence of severe complicating factors, even if the family requests it.  

For Trisomy 18 and 13, this is not yet the case. However, discussions have recently shifted from considering these conditions to be incompatible with life towards the type of treatment appropriate at birth to prolong life. Even as new research and treatments emerge, the practice of life-sustaining measures for trisomy 18 and 13 is likely to remain in the moral “gray zone” in which parental input is paramount. 

Although it is true that children with these conditions experience profound impairments, research shows that they can still achieve developmental milestones over time. More importantly, intellectual disability does not necessarily equate to an unacceptable quality of life.  

As families increasingly elect to pursue interventions for their children, providers must continue to create a non-judgmental environment that allows families to pursue the decision that is best for them at the time. 

By Shawn Pompa, MSN, APRN, CNM


  • Blakeley, C., Smith, D. M., Johnstone, E. D., & Wittkowski, A. (2019, August 8). Parental decision-making following a prenatal diagnosis that is lethal, life-limiting, or has long term implications for the future child and family: A meta-synthesis of qualitative literature – BMC medical ethics. BMC Medical Ethics.  
  • Centers for Disease Control and Prevention. (2022, November 18). Facts about down syndrome. Centers for Disease Control and Prevention.  
  • Cortezzo, D. M., Tolusso, L., & Swarr, D. (2022, April 19). Perinatal Outcomes of Fetuses and Infants Diagnosed with Trisomy 13 or Trisomy 18. The Journal of Pediatrics.  
  • Kett, J. (2020). Who Is the Next “Baby Doe?” From Trisomy 21 to Trisomy 13 and 18 and Beyond. Pediatrics.  
  • U.S. National Library of Medicine. (2022, September 3). Edwards Syndrome. Stat Pearls. 
  • U.S. National Library of Medicine. (2022, September 6). Down Syndrome. Stat Pearls. 
  • U.S. National Library of Medicine. (2022, October 16). Trisomy 13. Stat Pearls.
  • Support Organization for Trisomy 18, 13, and Related Disorders. (2023, Trisomy Awareness Month Proclamations 2023.