Starting Your Journey with Trisomy 18

Receiving a diagnosis of Trisomy 18—whether during pregnancy or after your baby is born—is often a moment of profound emotional shock. You may have been given information that feels final or overwhelming, and it is common to feel as though the future you imagined has shifted instantly. This page is designed to help you navigate those first steps, providing a foundation of modern medical understanding to help you advocate for your child and your family. If you received a prenatal diagnosis, your most pressing next steps are confirming the result with diagnostic testing and meeting with a maternal-fetal medicine specialist to plan your delivery.

It is important to know that Trisomy 18 is almost always caused by a random error in cell division. It is not caused by anything a parent did or did not do, and you are not to blame.

Defining Trisomy 18

Trisomy 18, also known as Edwards syndrome, is a genetic condition that occurs when a child has three copies of chromosome 18 in some or all of their cells, instead of the usual two [F002]. Chromosomes are the “instruction manuals” for the body, and having an extra set of instructions for chromosome 18 affects how a baby develops and grows [F005].

There are three main types of Trisomy 18:

• Full Trisomy 18: The extra chromosome is present in nearly all cells tested. This is the most common form [F002].
• Mosaic Trisomy 18: The extra chromosome is present in only some cells, while others have the typical two copies [F002].
• Partial Trisomy 18: Only a segment of chromosome 18 is tripled, often from an unbalanced chromosome rearrangement, rather than the entire chromosome [F002]. This may be present in all or some cells.

Understanding the Rarity

Trisomy 18 is considered a rare condition. While estimates vary depending on the study and the region, it occurs in approximately 1 in every 3,000 to 8,000 live births [F001]. Because it is uncommon, many local doctors or smaller hospitals may have limited direct experience with the condition [F059]. You may find yourself in the position of seeking out specialists at larger academic medical centers who have more extensive experience in managing the complex needs associated with this diagnosis.

The Shift Away from “Incompatible with Life”

In the past, Trisomy 18 was frequently labeled “incompatible with life” or “lethally” by the medical community. However, modern medical consensus has shifted significantly away from using these absolute terms [F051][F071].

Current ethical and clinical guidelines emphasize that:

• Survival is possible: While Trisomy 18 is associated with high mortality in the first year of life, some children survive into childhood and even adolescence [F020]^[1].
• Individualized care is essential: Decisions about medical care should be based on your child’s specific health needs and your family’s goals, rather than the genetic label alone [F049][F071].
• Shared decision-making: You are an essential part of the care team. Doctors are increasingly encouraged to work with parents in a shared decision-making process—a collaborative approach where medical evidence is combined with your family’s values to choose the best path forward [F052][F071].

Knowns and Unknowns

When you first receive a diagnosis, there are things research can tell us and things that remain uncertain for every individual child.

What research tells us (The Knowns):

• Multisystem Involvement: Trisomy 18 typically affects multiple organs. About 80% of liveborn infants have a congenital heart defect (a structural problem with the heart), and many also have challenges with breathing, feeding, or kidney function [F004][F062].
• High Early Mortality: Statistically, the risk of pregnancy loss or death in the first weeks of life is high [F019][F044].
• Developmental Delays: Children who survive beyond infancy will experience significant delays in reaching milestones, though their specific abilities vary [F024][F048].

What remains uncertain (The Unknowns):

• Individual Trajectory: Statistics cannot predict the exact path for your specific child. Outcomes vary widely based on which organs are affected and how severely [F065].
• Impact of Interventions: In the past, many life-prolonging treatments were withheld from children with Trisomy 18. Newer research suggests that interventions like heart surgery or intensive care can improve survival for some children, though these choices come with significant medical burdens [F022][F068].
• The Role of Mosaicism: If your child has the mosaic form, the percentage of extra chromosomes found in a blood test does not always accurately predict how their organs will function or how they will develop [F006][F063].

Palliative Care and Medical Intervention

It is a common misconception that choosing palliative care (specialized medical care focused on relief from symptoms and stress) means giving up on life-prolonging treatment. In modern medicine, these two approaches are not mutually exclusive [F054][F067].

Palliative care can be an “extra layer of support” that works alongside active medical treatments [F054]. They can help manage pain, assist with difficult decisions, and focus on the quality of life for your child and your entire family, regardless of whether you choose to pursue intensive surgeries or comfort-focused care [F027][F067]. Integrating these supports early can help ensure that your child’s care plan remains responsive to their needs and your family’s evolving goals [F054][F030].