- Video: Causes of Clefting
- Environmental Factors
- Genetic Factors
- What are the chances of having a child with a cleft?
What Causes a Cleft?
There is no one cause of cleft lip and/or palate. Research tells us it’s often caused by a combination of different genetic and environmental factors, but because of the huge number of factors involved it can be very difficult to narrow these down.
Genetics is all about things inherited from family members, like eye and hair colour. Sometimes there is a clear family link, other times it just happens as a ‘one off’.
Environmental factors mean things that happen just before or during pregnancy, like taking a certain medicine or how the baby starts growing in the womb.
Most of the time, a cleft is caused by genetic and environmental factors coming together in a way which can’t be predicted or prevented.
VIDEO: Easing the First Few Hours – Chapter Three – Causes of Clefting (5:16)
Around 15% of clefts are caused by syndromes, where one or more symptoms occur all together. If a syndrome is involved, the chances of passing on a cleft is all down to the heritability of the syndrome, which in some cases can be as high as 50%.
An isolated cleft palate (where the lip is not affected) is believed to have a different cause to cleft lip and palate. So a family affected by cleft palate (but not cleft lip) may only be likely to pass on cleft palate.
There are a huge number of factors that affect how likely someone is to have a cleft, including race, sex, and many different environmental factors that are almost impossible to predict without a careful look at an individual’s genetic history and circumstances.
There have been a number of environmental factors linked to a higher chance of a baby developing a cleft. These include well-known risks in pregnancy such as smoking and heavy alcohol consumption, as well as uncontrollable factors like the baby’s position in the womb. Certain medications have also been linked to a higher chance of cleft, such as particular anti-seizure medications, but these are not prescribed to pregnant women.
These environmental factors can interact with genes in different ways, causing them to ‘switch on or off’ as a baby develops in the womb.
It is important to note that these are just factors, and that the causes of cleft are usually much more complicated than what someone did or didn’t do while pregnant. Even the healthiest, best-planned pregnancies can result in a cleft, and this is no one’s fault.
To find out more about what may have caused your/your child’s cleft, see if your Cleft Team can arrange genetic testing (see below).
While some conditions can point to a single genetic factor as a cause, there have been a number of different genes identified as increasing the risk of having a child with a cleft.
It may also be a matter of certain environmental factors switching genes on or off as a baby is developing in the womb. This is called ‘epigenetics’.
Genetic testing (also called genetic counselling or evaluation) aims to work out how likely you are to pass on a trait such as cleft lip and/or palate. Parents may want to know how likely they are to have another child with a cleft, and adults with a cleft may want to know how likely they are to pass their cleft on to any future children.
It usually involves several steps, including putting together a detailed family history, medical history, a physical examination of the person affected and even laboratory testing. It all depends on the individual and what they’re looking for. The most important part of this for people with a cleft is confirming that the cleft is isolated and not part of a syndrome, as this will change how likely it is to happen again. The type and severity of a cleft also has to be considered, and this might be harder if there are different types in one family.
At the end of this session or series of sessions, the geneticist and/or genetic counsellor will tell you what they’ve found and if they think any further treatment is needed (in cases of a syndrome), and they will also be able to tell you how likely it is that you will pass on a cleft to any children.
Syndromes and Other Conditions
Sometimes a cleft is caused by part of a ‘syndrome’, which is when lots of different symptoms happen together. One of these symptoms can be a cleft lip, a cleft palate, or a cleft lip and palate.
There are over 400 conditions and syndromes that list a cleft as a symptom.
Some of these syndromes and conditions are very rare and usually occur as a ‘one off’, others have a 50% chance of being passed on.
Estimates can vary widely, but based on UK statistics, around 15-30% of clefts happen as part of a syndrome or condition.
What are the chances of having a child with a cleft?
Some conditions like Sickle Cell Anaemia are relatively easy to predict – we know which gene causes it, and we can work out the chances of a child inheriting the condition or being a carrier based on whether or not their parents are carriers. The causes of cleft lip and palate are much more complicated and vary greatly from case to case, so even if both parents have a cleft it can be very difficult to accurately predict how, if at all, their children will be affected. Each case needs to be looked at separately.
The below statistics are based on multiple studies looking at a range of different populations, but they are only observations, not predictions, and are subject to change depending on the available evidence. If you want to know more about your particular case, you should talk to your Cleft Team about genetic testing or evaluation.
1/700 people around the world will be born with a cleft lip and/or palate, though some statistics put it closer to 1/600.
This is around 0.14% of the population. A cleft is the most common craniofacial (to do with the skull or face) congenital (something you’re born with) abnormality in the world, and in the UK alone three babies are born with a cleft every day.
In general, the more people who have a cleft in a family, and the closer they’re related to a child, the more likely that child is to have a cleft. However, the causes of clefting vary so much that it’s extremely hard to predict how future children will be affected without detailed genetic analysis.
Parents with a cleft
If there is one parent with a cleft, the likelihood of a child having a cleft is between 2-8%, although in some cases depending on the cause of the parent’s cleft it can be as high as 50%.
If a parent is affected as well as their own parent, sibling or existing child, the likelihood of future children having a cleft is around 10-20%
It is important to remember that a cleft may be caused by another condition or syndrome which has not been diagnosed, in which case the chances of inheriting the cleft will be very different.
Siblings and other relatives with a cleft
While having a lone affected uncle, aunt, cousin or another more distant relative does increase the likelihood of having a child with a cleft, it’s estimated to be by less than 1%.
Siblings of a person with a cleft only have around a 1% chance of passing this on. This goes up to 5-6% chance if they have other affected close family members.
Where there is no family history and the cleft was not caused by a syndrome or condition, the likelihood of having a child with a cleft is around 0.14%, or 1/700.
If neither parent has a cleft, but they have one child with a cleft, the likelihood of another child also having a cleft is 2-8%, and this goes up the more children with a cleft they have.
If someone else in the family (such as an uncle or aunt) also has a cleft, this goes up to 10-12%.