Trisomy 13 and 18: Why Two Babies With the Same Diagnosis Can Have Very Different Futures

What four studies from Texas, Vienna, Istanbul and Rome, published between September 2025 and February 2026, tell families

A diagnosis that has been changing quietly for a decade

Trisomy 13 and trisomy 18 are conditions in which a baby is born with an extra copy of a whole chromosome, and for decades families were told the diagnosis was simply fatal. Four studies published between September 2025 and February 2026 tell a more hopeful story: how long these children live depends on the exact genetic pattern, on the baby's own strength, and on the treatment policy of the hospital where they are born.

Chromosomes are the packages that carry our genes. Most people have two copies of each. In trisomy 13 (sometimes called Patau syndrome) and trisomy 18 (Edwards syndrome), there are three copies of chromosome 13 or chromosome 18. The extra genetic material affects the way many organs form before birth, and most affected babies have heart defects, differences in brain structure, feeding difficulties, and slow growth in the womb.

The four studies, and what each one looked at

The first study is the largest [1]. Researchers used the Texas Birth Defects Registry — a statewide system that reviews hospital records to find every baby born with a birth defect — to follow 798 babies born between 1999 and 2008 for ten years. The second followed 193 pregnancies at a single large hospital in Vienna, Austria, over 18 years, in a unit that deliberately does not offer breathing machines or major surgery to these babies [2]. The third described 29 children cared for over ten years at a specialist maternity and children's hospital in Istanbul, Türkiye, where national rules mean that families cannot ask for life-sustaining treatment to be withheld [3]. The fourth compared 32 children at Bambino Gesù Children's Hospital in Rome, Italy, where both intensive treatment and comfort-focused care were genuinely available, so the two approaches could be compared [4].

What families used to be told, and why it was incomplete

For most of the past thirty years, the survival figures families heard came from large national registries. A study across several American states found that most babies with these conditions lived only days, and that roughly one in ten reached their first birthday [5]. That single sentence shaped an enormous number of conversations — and it also shaped medical practice, because if a condition is believed to be uniformly fatal there seems little reason to offer heart surgery or intensive care. For years, many hospitals did not.

The picture began to shift in 2016, when a study using health records from the Canadian province of Ontario found that children who had surgical operations lived much longer than those who did not, and that about one in ten survived to ten years of age [6]. This was widely reported as evidence that surgery saves these children. But two experienced clinical geneticists pointed out a problem that still matters today: doctors offer surgery to the healthiest babies [7]. So comparing operated with non-operated children is a little like comparing the exam results of students who were selected for extra tuition with those who were not — the groups were different before anything was done to them. A European study covering many national registries then showed that children who survive the first year tend to keep going, forming a stable group of longer-term survivors rather than continuing to die steadily [8]. Meanwhile, an international comparison found that survival varied considerably from country to country, which was an early hint that local practice, not just biology, was part of the story [9].

The genetic detail that changes the odds

The Texas study asked a question nobody had answered at this scale: does it matter which kind of trisomy a child has [1]? Most children with these conditions have the extra chromosome in every cell of their body — "full" trisomy. But some have it in only some cells (called mosaicism), and some have an extra copy of only part of the chromosome (partial trisomy).

The difference turned out to be large. Taking all children together, about 8.5 in 100 with trisomy 13 and 8.6 in 100 with trisomy 18 were alive at ten years — the familiar figure. But among children with mosaic or partial trisomy, 25 in 100 with trisomy 13 and nearly 44 in 100 with trisomy 18 reached ten years, compared with about 5 in 100 and 7 in 100 among those with full trisomy. To put that in plainer terms: for a child with mosaic or partial trisomy 18, the chance of reaching their tenth birthday was closer to one in two than to one in twelve. This held true even after the researchers accounted for prematurity, birth weight, growth in the womb, heart defects and the mother's age.

If your child's genetic report mentions mosaicism or a partial trisomy, this is worth raising with your team. The general statistics that appear in leaflets and websites may substantially understate your child's chances. At the same time, the researchers were careful to note that genetics explained less than half of the survival difference — so a mosaic result is important information, not a guarantee.

The same condition, two very different hospitals

The Vienna and Istanbul studies read almost like descriptions of different diseases, even though the children's chromosomes were similar.

In Vienna, most families learned the diagnosis early, at around 14 weeks of pregnancy, and 83 in every 100 chose to end the pregnancy [2]. Among those who continued, about two-thirds of babies died before birth. Eleven babies were born alive. Because that hospital's policy is to provide comfort care — warmth, feeding support, pain relief — rather than breathing machines or major operations, survival ranged from six minutes to 60 days, with a middle value of 18 hours. Three babies had a feeding tube; none had surgery. Two babies went home with a community palliative care team supporting the family.

In Istanbul, only one child in five was diagnosed before birth, and the law does not allow treatment to be withheld, so every medically indicated treatment was given [3]. Children lived a middle value of 90 days (trisomy 18) and 120 days (trisomy 13), and roughly a quarter to two-fifths were alive at one year. But the study also counted the cost of that path honestly: across the group there were 39 intensive care admissions, 514 days spent in hospital in the first month of life alone, and nine children died of infections caught in hospital. None of the children who developed those bloodstream infections survived.

Neither approach is presented here as the right one. What the contrast shows is that a survival figure is partly a description of a hospital, not only of a child.

Does more treatment mean more time?

The Rome study is the one that tested this most directly, because both routes were open there [4]. Of 32 children with trisomy 18, 23 received intensive treatment — heart surgery, a breathing machine, or intensive care — and 9 received comfort-focused care. Over the first thirty months, there was no significant difference in survival between the two groups. Overall, 73 in 100 were alive at four weeks, half at one year, and a quarter at ten years; the longest-lived child in the study reached 19 years and 5 months.

What did predict survival was the child rather than the treatment: being born very small, being born early, having a major heart defect, and needing several medical devices at home were all linked to shorter survival. Heart surgery was the one clear exception, and in an instructive direction. For children with major, complex heart defects, surgery did not lengthen life. For children with simpler heart defects, it did, and full repair worked better than a temporary, patch-up operation. This fits with long-term follow-up of children who have had heart procedures [10] and with the advice of a 2023 expert group of heart surgeons, who recommended that decisions be based on the individual child's heart anatomy rather than on the diagnosis printed at the top of the chart [11].

What this means for families, and what comes next

Three things follow for parents facing this diagnosis. First, ask for the detail of the genetic result — full, mosaic, or partial — because it changes the realistic outlook [1]. Second, ask your team directly what your hospital does and does not offer, and ask whether a different centre would offer something different; specialists in this field have argued for years that this kind of openness is part of good, patient-centred counselling [12]. Third, ask about burden as well as time — nights at home, comfort, hospital days, and what daily life is likely to look like. Parents who have raised children with these conditions consistently describe those things as central to how they judge their child's life [13], and studies of what happens before and just after birth show how much of the picture is set very early [14].

Researchers are now working towards larger studies that record the exact genetic subtype, the precise heart anatomy, the hospital's stated policy, and standardised measures of a child's quality of life — so that families can be given a genuinely personalised picture rather than an average. Teams are also building the interdisciplinary model these families need, bringing obstetrics, neonatology, cardiology, genetics, surgery, palliative care and psychological support into one plan [15]. Our companion article on perinatal palliative care describes what that support can look like. The most important message from these four studies is that "incompatible with life" is no longer an accurate description — and neither is any single number.

References

  1. Ludorf KL, Benjamin RH, Shumate CJ, Canfield MA, Nguyen J, Agopian AJ. Long-Term Survival Among Children With Trisomy 13 and Trisomy 18 by Cytogenetic Status. JAMA Netw Open. 2025;8(9):e2529885. doi:10.1001/jamanetworkopen.2025.29885 ↩
  2. Reischer T, Dorittke T, Klebermaß-Schrehof K, et al. Clinical course and perinatal management of fetuses and newborns affected by trisomy 13 and 18: a retrospective single-centre cohort study. Eur J Pediatr. 2025;185(1):30. doi:10.1007/s00431-025-06614-7 ↩
  3. Uygur Külcü N, Erol N, Oguz S, Celayir A, Karatekin G, Yatır Alkan Ö. Trisomy 18 and Trisomy 13: A Retrospective Cohort Study at a Tertiary Hospital. Children (Basel). 2026;13(2):271. doi:10.3390/children13020271 ↩
  4. Caggiano S, Persia S, D'Amore F, et al. Survival in infants with trisomy 18, palliative care and ethical reflections: a single center considerations. Ital J Pediatr. 2026;52(1):16. doi:10.1186/s13052-025-02181-7 ↩
  5. Meyer RE, Liu G, Gilboa SM, et al. Survival of children with trisomy 13 and trisomy 18: A multi-state population-based study. Am J Med Genet A. 2016;170A(4):825-837. doi:10.1002/ajmg.a.37495 ↩
  6. Nelson KE, Rosella LC, Mahant S, Guttmann A. Survival and Surgical Interventions for Children With Trisomy 13 and 18. JAMA. 2016;316(4):420-428. doi:10.1001/jama.2016.9819 ↩
  7. Kosho T, Carey JC. Does medical intervention affect outcome in infants with trisomy 18 or trisomy 13? Am J Med Genet A. 2016;170A(4):847-849. doi:10.1002/ajmg.a.37610 ↩
  8. Glinianaia SV, Rankin J, Tan J, et al. Ten-year survival of children with trisomy 13 or trisomy 18: a multi-registry European cohort study. Arch Dis Child. 2023;108(6):461-467. doi:10.1136/archdischild-2022-325068 ↩
  9. Goel N, Morris JK, Tucker D, et al. Trisomy 13 and 18—Prevalence and mortality—A multi-registry population based analysis. Am J Med Genet A. 2019;179(12):2382-2392. doi:10.1002/ajmg.a.61365 ↩
  10. Peterson JK, Kochilas LK, Catton KG, Moller JH, Setty SP. Long-Term Outcomes of Children With Trisomy 13 and 18 After Congenital Heart Disease Interventions. Ann Thorac Surg. 2017;103(6):1941-1949. doi:10.1016/j.athoracsur.2017.02.068 ↩
  11. St Louis JD, Bhat A, Carey JC, et al. The American Association for Thoracic Surgery (AATS) 2023 Expert Consensus Document: Recommendation for the care of children with trisomy 13 or trisomy 18 and a congenital heart defect. J Thorac Cardiovasc Surg. 2024;167(5):1519-1532. doi:10.1016/j.jtcvs.2023.11.054 ↩
  12. Haug S, Goldstein M, Cummins D, Fayard E, Merritt TA. Using Patient-Centered Care After a Prenatal Diagnosis of Trisomy 18 or Trisomy 13: A Review. JAMA Pediatr. 2017;171(4):382-387. doi:10.1001/jamapediatrics.2016.4798 ↩
  13. Janvier A, Farlow B, Wilfond BS. The experience of families with children with trisomy 13 and 18 in social networks. Pediatrics. 2012;130(2):293-298. doi:10.1542/peds.2012-0151 ↩
  14. Cortezzo DE, Tolusso LK, Swarr DT. Perinatal Outcomes of Fetuses and Infants Diagnosed with Trisomy 13 or Trisomy 18. J Pediatr. 2022;247:116-123.e5. doi:10.1016/j.jpeds.2022.04.010 ↩
  15. Weaver MS, Anderson V, Beck J, et al. Interdisciplinary care of children with trisomy 13 and 18. Am J Med Genet A. 2021;185(3):966-977. doi:10.1002/ajmg.a.62051 ↩