Genetics

One of the most common questions adults who were born with a cleft have is whether their children will be born with one too. This section provides an overview of the genetic component of cleft, as well as the support services available. It’s worth noting that you do not have to be in a relationship or thinking about having children right away to access these services.

If you’re thinking about starting a family of your own, you may be wondering if any future children of yours will inherit your cleft and how this might affect both them and you.

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 from case to case. 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, however these are only observations, not predictions. While we can tell you how many adults with a cleft have gone on to have children with a cleft, this information can’t tell you anything about your individual circumstances without genetic testing.

If you want to know more about your particular case, you should talk to your Cleft Team about genetic testing or evaluation.

How likely is a cleft?

1/700 people 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) abnormality in the world, and in the UK alone around three babies will be 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, it should be noted that some studies put the number of ‘one-off’ cases in a family as high as 50-75% amongst certain populations, so it’s extremely hard to predict without genetic analysis.

If just one parent has a cleft, around 2-8% of their children will have a cleft too. In some cases, depending on the specific cause, this can be as high as 50%. Remember, this doesn’t mean that there’s a necessarily a ‘2-8% chance’ of you passing on your cleft, just that according to the numbers we have available, a cleft is passed on in 2-8% of cases.

If a person is affected as well as their own parent, sibling or existing child, around 10-20% will go on to have children with a cleft.

If there is just one affected sibling (and both parents are unaffected), it’s around 4%, and this goes up to around 9% if there are two affected siblings.

While having a lone affected uncle, aunt, cousin or another more distant relative does increase the chances of a cleft, it’s estimated to be by less than 1%.

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%. If someone else in the family (such as an uncle or aunt) also has a cleft, this goes up to 10-12%.

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 family members.

Around 30% 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 how likely a child is to inherit that specific syndrome, which in some cases can be as high as 50%.

It’s not as simple as that, though. An isolated cleft palate (where the lip is not affected) is believed to have a different cause to cleft lip and palate. So family affected by cleft palate (but not cleft lip) may only be at risk of passing 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.

Environmental Factors

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, heavy alcohol consumption, obesity and poor nutrition. A lack of folic acid has also been linked to cleft, but there is no firm evidence that a higher consumption of folic acid will reduce the chances of a cleft.

It is important to note that these are just factors, and that the causes of cleft are often much more complicated than this. Even the healthiest, well-planned pregnancies can result in a cleft forming.

You should always talk to a doctor about medications or other environmental concerns when planning a pregnancy, and this is true whether or not you have a medical issue like a cleft.

What is Genetic Testing?

Genetic testing (also called genetic counselling or evaluation) aims to work out how likely you are to pass on a trait, in this case your cleft.

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.

You can find out more about genetic testing and counseling on the NHS Choices website, or by contacting your Cleft Team.

Click here for our ‘Genetics & Decision Making about Having Children’ cleft talk podcast

FAQs

What causes a cleft?

• We don’t fully understand how a cleft is caused.
• What we do know is that a cleft can be caused by many different factors, most of which are not in our control.
• Cleft can occur by itself or as part of a wider condition.
• Most clefts are caused by multiple factors. This is usually a combination of the genes we inherit from our parents and the environment we are exposed to during pregnancy.
• Some examples of environmental exposure could include hyperthermia (being too hot), stress, maternal health, lifestyle and diet factors, occupational exposures and infection.
• A cleft is not anyone’s ‘fault’. Even the most carefully planned pregnancies can result in a child having a cleft.

 Will my child(ren) be born with a cleft?

• In around 1 in 50 cases, adults born with a cleft who have no other affected family members will pass this it to their children.
• Generally speaking, the more people who have a cleft in your family and the closer they are to you in your family tree, the more likely you are to pass it on.
• This chance can be higher if your cleft is the result of a syndrome.
• A genetic specialist (like a Consultant Geneticist or Genetic Counsellor) will be able to help you understand your specific situation and give appropriate advice.

 What is Genetic Counselling?

• Genetic Counselling provides support, information and advice about genetic conditions.
• Genetic testing can be used to find out whether a person is carrying a specific altered gene (genetic mutation) that causes a particular medical condition such as cleft.
• A genetic counsellor will often start by drawing a family tree to determine any history of cleft or other condition in your family to give you an idea of the likelihood of your child having a cleft.
• Sometimes they may choose to do a saliva or blood test to check for specific syndromes or conditions.
• Most people find genetic counselling to be a reassuring experience.
• If there is another condition in your family that you are concerned about, you can let the geneticist know whether you would like to know more about this.
• M ore information on Genetic Counselling is available on the NHS website: nhs.uk/conditions/genetics/services/.

 How do I access Genetic Counselling?

• You can access Genetic Counselling through your Cleft Team. If you’re currently being seen by someone else on the team, at your next appointment you can ask to be referred to the Geneticist.
• You can access Genetic Counselling at any time. You do not have to wait until you are in a relationship and planning to have children to see the genetic specialist.
• As Genetic Counselling is part of NHS cleft treatment, it is free of charge.