Produced by the Centre for Genetics Education. Internet: http://www.genetics.edu.au
TRISOMY 13 — PATAU SYNDROME
Produced by the Centre for Genetics Education. Internet: http://www.genetics.edu.au

FACT SHEET
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Important points
Trisomy 13 (also known as Patau syndrome) is a chromosomal condition in which there are three copies instead of the usual two copies of all, or a part of chromosome 13 in the cells of the body
Trisomy 13 severely impacts on intellectual and physical development
Appears to affect females slightly more frequently than males
Occurs in about 1 in 5,000 to 1 in 12,000 live births
About 1% of all recognised miscarriages occur in association with trisomy 13
Of all babies born with the extra copy of chromosome 13 in all the cells of their body, around 50% die in the first month, and the rest within the first year
The chromosomal problem in trisomy 13 is due to an egg cell or, rarely, a sperm cell, that is formed containing one copy of each chromosome and an extra copy of chromosome 13, ie. 24 chromosomes rather than 23. When that egg combines with sperm containing the usual 23 chromosomes, the baby conceived has 47 chromosomes in the cell of their body rather than the usual 46
When there are three copies of chromosome number 13 in all of the baby’s cells, the condition is referred to as trisomy 13
When the extra copy of chromosome 13 is only in some of the baby’s cells due to a mistake in cell division occurring soon after conception, the chromosomes in the cells of the baby may show two different patterns: some cells with 46 chromosomes and some with 47: mosaic trisomy 13. The range and severity of symptoms depends on the number and distribution of cells containing the extra copy of chromosome 13
The chance of having a child with trisomy 13 increases with the mother’s age
If a woman has had a child with trisomy 13 there may be a small additional