What is Patau's syndrome?
Patau's syndrome is a rare abnormality where a baby develops with too many chromosomes.
Chromosomes contain all the genetic material to help human cells divide and eventually grow into a baby
(NHGRI 2015). Healthy babies are born with 46 chromosomes, arranged in 23 pairs. Babies with Patau's syndrome have an extra copy of chromosome 13 in every cell of their body. Patau's syndrome is also called trisomy 13. It is the most severe of all chromosomal abnormalities
(Best 2017).
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There are several forms of trisomy 13:
- Full trisomy 13: full Patau's syndrome is the most common and most severe form of the condition, where every cell in the body has an extra chromosome 13.
- Translocational trisomy 13: an inherited form of the syndrome where part of chromosome 13 becomes attached to another chromosome. This type accounts for about one in five cases of Patau's syndrome.
- Mosaic trisomy 13: a less severe and rarer form of the syndrome, where some cells have an extra chromosome 13 instead of every cell.
- Partial trisomy 13: another rare form of the condition, which happens when a section of extra chromosome, rather than a whole one, is present in the cells.
(GARD 2016)
About 150 babies with Patau's syndrome are born in the UK each year. Patau's syndrome causes such serious complications that, sadly, most affected babies are lost during pregnancy
(Best 2017, NHS 2016).
Babies born with Patau's syndrome usually only survive for a few days
(Best 2017, Tidy 2016). Rarely, a few babies with the less severe forms of the syndrome live beyond a year
(NHS 2016).
It's possible, but unusual, for some children to survive into their teens
(Best 2017) (NHS 2016). Babies with Patau's syndrome have major physical and mental disabilities and severe health problems
(Best 2017, NHS 2016, Tidy 2016).
What causes Patau's syndrome
The causes are unknown, but the risk of having a baby with Patau's syndrome increases as you become older
(Best 2017, NHS 2016).
Full trisomy 13 happens randomly due to a genetic abnormality in an egg or sperm prior to conception
(GARD 2016). As the fertilised egg starts to grow, it causes an error during cell division resulting in an extra chromosome 13
(GARD 2016, NHS 2017).
This error happens by chance. It isn't caused by anything that you have done and it does not run in families
(NHS 2016). Nevertheless, there is some evidence that your risk of having another pregnancy affected by trisomy 13 is slightly higher than it would be for a woman who had not had a trisomy 13 pregnancy before. The reasons for this are unclear
(GARD 2016, Tidy 2016).
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Translocational Patau's syndrome, when an extra copy of chromosome 13 attaches itself to another chromosome, can be inherited. If you or your partner have this rearrangement of chromosomes, there is an increased chance of passing it on to your children
(GARD 2016). You can find out how likely this is by having a blood test called a karyotype. A karyotype looks at chromosomes under a microscope
(GARD 2016, SOFT UK nd).
You should be offered genetic testing and counselling if your pregnancy or baby is affected by Patau's syndrome
(NHS 2016). This can help you plan for future pregnancies.
How will I find out if my baby has Patau's syndrome?
Screening for Patau's is offered to all pregnant women. The
combined screening test, or the more accurate
non-invasive prenatal testing (NIPT) (NHS 2016, 2018), will tell you your risk of having a baby with Patau's syndrome.
The combined screening test comprises a blood test and a
nuchal translucency (NT) ultrasound scan. It is offered alongside your dating scan, at about 12 weeks.
If you have a higher chance result from the combined screening test, you'll be offered NIPT or a diagnostic test
(RCOG 2020). NIPT is available on the NHS in England, Scotland and Wales
(NHS Inform 2019, PHE 2021, PHW 2018) and can give you a more accurate screening result than the combined test
(RCOG 2020). Screening tests tell you about the chances that you're expecting a baby with Patau's syndrome, but only a diagnostic test can confirm whether or not your baby is affected
(RCOG 2020). Depending on your stage of pregnancy, you'll be offered:
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If you miss screening for Patau's syndrome, your mid-pregnancy anomaly scan will pick up signs of the condition, which include:
- Severe heart defects.
- Brain abnormalities. Babies affected by Patau's syndrome have small heads (microcephaly), and their brains do not divide into two halves properly.
- Cleft lip and palate and eye abnormalities.
- Anatomical abnormalities, such as extra fingers or toes.
- Abnormalities affecting the organs, such as part of the bowel growing outside of the body and hernias.
- Kidney problems and unusually sized genitals.
(Best 2017, NHS 2016)
Sadly, because of the seriousness of Patau's syndrome, most babies are lost to miscarriage. When a baby survives into the second trimester, many parents-to-be make the difficult decision to end the pregnancy
(Tidy 2016).
Whatever your decision, your medical team will offer you support and advice. They should give you all the information you need to make the right decision for your family at a traumatic and isolating time
(ARC nd a, NHS 2016).
Some parents choose to prepare for the birth and the days, possibly longer, with their baby. Depending on the type and severity of Patau's syndrome, your baby is likely to need intensive care to help with life-threatening conditions, such as heart problems, breathing and feeding difficulties
(NHS 2016).
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You are likely to face difficult discussions with your baby's medical team about getting the right balance between treating your baby, and allowing him to be free of further medical interventions
(Best 2017, Tidy 2016). It's important to have as much information as possible, so you can think through and talk about what's best for you, your baby and the rest of your family
(ARC nd b).
Where can I get help and support?
