Trisomy 13, also called Patau syndrome, is fatal in the vast majority of cases. The median survival after birth is 7 to 10 days, and roughly 87% of live-born infants do not survive their first year. However, the condition is not universally lethal: about 10% of babies live past age one, and a small number survive into childhood or, rarely, into adulthood, depending on the genetic form and the medical interventions they receive.
How Most Infants Are Affected
Trisomy 13 involves an extra copy of chromosome 13 in every cell, which disrupts the development of nearly every major organ system. The brain, heart, and kidneys are hit hardest. Between 24% and 45% of infants have a severe brain malformation where the forebrain fails to divide into two hemispheres properly. Heart defects are present in the large majority of cases. These overlapping problems are what make the condition so dangerous so early in life.
About half of live-born infants with trisomy 13 die within the first week, and roughly half of those deaths occur on the very first day. The most common cause of death is cardiopulmonary arrest, which accounts for about 69% of fatalities. Congenital heart disease causes another 13%, and pneumonia about 4%.
Survival Beyond Infancy
While the numbers are stark, they are not absolute. A multi-state U.S. study following births from 1999 to 2007 found that 5-year survival for children with trisomy 13 was 9.7%. Some children survive into their second decade of life, though this remains uncommon. These longer survival cases have shifted the conversation among some medical teams, prompting consideration of more active treatment rather than comfort care alone.
Why the Genetic Type Matters
Not all trisomy 13 cases are genetically identical, and the specific type has a major impact on prognosis. There are three forms:
- Full trisomy 13: Every cell carries the extra chromosome. This is the most common form and has the worst outlook.
- Mosaic trisomy 13: Only some cells have the extra chromosome, while others are normal. Symptoms are often less severe.
- Partial trisomy 13 (translocation): Only part of the extra chromosome is present, attached to another chromosome.
A 2024 cohort study published in JAMA Network Open tracked 798 infants with trisomy 13 or 18 and found that children with mosaic or partial forms of trisomy 13 had a 25% chance of surviving to age 10, compared to just 4.9% for those with the full form. Children with full trisomy faced double the mortality risk over that same period. This is the single biggest factor in whether a child with trisomy 13 has a chance at longer-term survival.
The Role of Heart Surgery
Heart defects are central to the prognosis, and the decision about whether to surgically repair them has a measurable effect on survival. A study of children with trisomy 13 and 18 who underwent heart procedures found that those who received corrective surgery had a median survival of 32.2 years, while those who received only palliative procedures had a median survival of 10.1 years. Both numbers are dramatically higher than the overall median of 7 to 10 days, but they reflect a highly selected group: children healthy enough to be considered surgical candidates in the first place.
This is an area of active debate in medicine. Historically, the standard approach was comfort-focused care only, given the overall prognosis. But as data on longer-term survivors has accumulated, some families and medical teams are choosing to pursue surgical interventions, particularly for children with mosaic or partial forms.
What Life Looks Like for Survivors
Children who survive beyond infancy face significant developmental challenges, but they are not without abilities. Global developmental delays are expected across the board. Most children with trisomy 13 do not learn to speak words. However, many parents report their children communicate through body movements, facial expressions, and vocalizations. Receptive language, the ability to understand what others are saying, is often a relative strength.
Physically, many children can eventually learn to roll over and sit without support. They show preferences for certain people and objects. Vision and hearing problems are common and can complicate developmental progress further. The range of outcomes varies widely, particularly between those with full trisomy and those with mosaic or partial forms.
Pregnancies With Trisomy 13
The survival statistics above apply only to live births, but many trisomy 13 pregnancies never reach that point. A significant proportion end in miscarriage or stillbirth. When trisomy 13 is detected on prenatal screening, families face difficult decisions with limited time. The severity of organ malformations visible on ultrasound, along with the genetic subtype if known, can help clarify the likely outcome, though considerable uncertainty remains in individual cases.