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Trisomy 13/18 Info for Parents

Edwards' syndrome (trisomy 18) and Patau's syndrome (trisomy 13) are genetic conditions caused by the presence of an extra chromosome in the body’s cells. This extra genetic material affects fetal development. These syndromes are not diseases and, except in rare cases, they're not hereditary conditions. Instead they both occur by chance at conception.

Although it's been more than 50 years since researchers first identified the chromosomal nature of these conditions, we still don't know what causes the presence of an extra chromosome. It is not something you've done, or not done. It can happen to anyone.

How many babies are affected?

  • Trisomy 13 and trisomy 18 births occur about once in every 1,800 pregnancies and are the most common autosomal trisomies after trisomy 21, which is also known as Down's syndrome.
  • In England and Wales between 2004 and 2011, there were 4,028 diagnosed cases of trisomy 18 and 1,662 of trisomy 13.
  • In the same 8 year period, 372 babies with trisomy 18 were born alive as were 173 with trisomy 13.

(National Down Syndrome Cytogenetic Register, data provisional).

What is the likely outcome for a baby diagnosed with these conditions?

Parents who receive a diagnosis for their baby are faced with making complex and difficult decisions. You may be asking yourself what the quality of life will be like for your baby. You may also be considering what the impact will be on the whole family as you care for your affected child. Parents often feel that there is little time to gather the information they need to make such life-changing decisions. 

It is a sad reality that most babies will not survive for a long time and will have significant care needs. But there are a few long-term survivors who beat the odds, even living into adulthood.

  • Average survival times for babies born alive with full trisomy 18 and full trisomy 13 are two weeks or less.
  • Despite the low average survival times almost 1 in 5 live born infants survive three months.
  • 8% of babies born alive live for at least a year.
  • Infants with the less common mosaic and partial forms tend to survive for longer - your local genetic service can advise you on an individual karyotype. Related disorders.
  • Newborns with Edwards' syndrome or Patau's syndrome are more likely to have significant problems with different organ systems and their care needs are likely to be high. Caring for your child.
  • In England and Wales about 6 in every 10 diagnosed pregnancies will be terminated early. Termination.
  • When supported by other families, most parents feel that the overall experience of their child's life is positive and that their family is enriched. These parents did acknowledge the challenges brought by the extra financial costs of caring for a child with a disability. Read the research.

What is the risk of a pregnancy bring affected?

  • About 1 in 200 births result in a baby with a chromosome defect. 
  • The age of the mother is the major known risk factor for having a baby with Edwards' syndrome or Patau's syndrome. 
  • There is a small increased risk of the same trisomy after a previous pregnancy with trisomy 13 or trisomy 18. There may also be a small increased risk for women with a previous pregnancy with trisomy 21 (Down's syndrome)
  • Except in rare inherited cases, chromosome defects are usually one-off events.

You may wish to discuss the option of prenatal diagnosis if you become pregnant in the future or if you have had a previous pregnancy with a trisomy.