Patau’s syndrome

Patau's syndrome, also known as Trisomy 13, is a rare but serious genetic condition. It starts to affect babies while they're still in the womb, and it goes on causing health problems throughout their lives.

In the UK, around 2 in every 10,000 births are affected by Patau's syndrome.

A baby inherits genetic material from both parents when they are conceived (made). This genetic material is carried in structures called chromosomes.

Humans normally have 23 pairs of chromosomes. In each pair, 1 chromosome comes from the mother and 1 comes from the father.

A baby with Patau's syndrome has inherited an extra copy of chromosome 13. The extra copy may be present in some or all of the baby's cells, and it can lead to health problems for the baby.

There are 3 different forms of Patau's syndrome.

In full form, the baby has inherited a complete extra copy of chromosome 13, and it is present in all of the baby's cells. Around 80% of babies born with Patau's syndrome have this full form.

In mosaic form, the baby has also inherited a complete extra copy of chromosome 13, but the copy is only present in some of the baby's cells.

In partial form, the baby has inherited only part of an extra copy of chromosome 13. This is a very rare form of Patau's syndrome.

In most cases of Patau's syndrome, the cause is a random change in the egg or sperm, and the parents themselves are healthy. Nothing the parents did before or during the pregnancy caused this change.

You'll be offered screening for Patau's syndrome when you're between 11 and 14 weeks pregnant. The screening test shows whether your baby has a high or low chance of having Patau's syndrome.

If screening shows a high chance, you can choose to have a further diagnostic test if you wish.

If your result is a very high chance (between "1 in 2" and "1 in 10" for Patau's syndrome), this may affect your options for further screening. NIPT is less accurate when someone has had a very high chance result for Edwards' syndrome or Patau's syndrome. Your doctor will talk through the next options with you.

No test can tell whether your baby has full, mosaic or partial Patau's syndrome, or how they'll be affected.

Around 7 in 10 (70%) of pregnancies diagnosed with Patau's syndrome from screening tests will end in miscarriage or stillbirth. The risk of miscarriage falls as the pregnancy goes on, but there's still a risk of stillbirth.

If your baby has Patau's syndrome, it's likely they will have some health conditions. Exactly how your baby is affected depends on the form of Patau's syndrome they have.

Full form Patau's syndrome is considered a life-limiting condition. This means it can affect how long a baby can live.

Around 4 in 10 (43.1%) babies with full form Patau's syndrome will live longer than 1 week. Around 1 in 10 (9.7%) will live longer than 5 years.

Babies born with full form Patau's syndrome will have a learning disability that may be severe. They're also likely to have a wide range of health conditions, and some of these can be serious. Statistically:

• around 8 in 10 (80%) will have heart issues
• around 6 in 10 (60%) will have cleft lip and/or palate
• around 6 in 10 (60%) will have issues with brain development
• around 5 in 10 (50%) will have seizures
• around 5 in 10 (50%) will have hearing loss
• around 5 in 10 (50%) will have joint contractures (shortening of muscle tissue that can cause a deformity)
• around 5 in 10 (50%) will have eye issues or an absent eye

At present, doctors can't predict how babies with mosaic or partial forms of Patau's syndrome will be affected. This is because it depends on:

• how many cells contain the extra chromosome (mosaic)
• how much of the extra chromosome they have (partial)

Some babies may have severe health problems like those seen in full form Patau's syndrome. Others may have much less serious health issues. There are even cases where the baby seems to have no health issues at all.

Most babies with a form of Patau's syndrome will have some form of learning disability.

Life expectancy for babies with mosaic or partial forms of Patau's syndrome also varies a great deal. Some will live long lives, while others will have a much shorter life expectancy.

Every child is different, and Patau's syndrome affects each one in its own way. Like any other child, a child with Patau's syndrome has a personality of their own, with likes and dislikes and the little things that make them who they are.

Babies with full form Patau's syndrome are usually born with a low birthweight and are called "medically fragile". This means they are at high risk of infections and of complications that need treatment in hospital. They may also:

• have difficulty feeding and may need to be fed by a tube
• have difficulty breathing and have apnoea (pauses in their breathing)

Their needs are complex, but children with Patau's syndrome can still make progress with their development, although it is slow.

Many children are reported to be able to communicate their needs and show awareness of their surroundings, and some can sit and stand with support. There are also cases of older children attending school.