What Is a Cleft Lip and a Cleft Palate?
Cleft lip and cleft palate are the most common congenital anomalies of the face and skull, affecting approximately one in 700 newborns in the U.S. Cleft lip is a partial or complete gap (cleft) in the lip caused by incomplete merging of the middle and side portions of the lip during pregnancy. The gums may or may not be involved in cleft lip. Cleft palate is a partial or total separation (cleft) of the left and right sides of the roof of the mouth during pregnancy. When cleft lip and cleft palate occur together the condition is called cleft lip and palate. When they occur alone the conditions are called isolated cleft lip and isolated cleft palate. This terminology can sometimes get confusing. The combinations of cleft lip and cleft palate and their percentage of all cleft lip and cleft palate cases are shown below.
Isolated Cleft Lip (21%)
Cleft Lip and Palate (46%)
Isolated Cleft Palate (33%)
These percentages show that the majority of patients who have a cleft lip also have a cleft palate. Patients with bilateral cleft lip will have a cleft palate in about 85% of cases. Patients with unilateral cleft lip will have a cleft palate in about 70% of cases. The differences between unilateral cleft lip and bilateral cleft lip and how they occur are explained in the section Cleft Lip Anatomy.
Causes of Cleft Lip and Palate
There are several factors that may increase the risk of having a child with cleft lip and palate. There are many genes that may be passed on to the child from either parent that may increase the child's risk of having a cleft of the lip and/or palate. Having one or more of these genes does not mean that the child will definitely have a cleft. A simplified way to think about it is that there are many, many genes that slightly increase someone’s risk of having a cleft lip and/or palate. The more of these genes a person has, the higher the chances are that they will have a cleft. Similarly, the more of these genes that each parent has and passes on to their children will increase the risk of their children also increases. However, it is important to understand that in most cases, a family with a parent or child with a cleft still has a low risk of having more children with clefts of the lip and palate. The risk is just higher than that of the average family (1 in 700).
The most common scenario is that a family will have a child born with a cleft and no other history of a person with cleft lip and palate in either parent’s family. The risk of this family’s next child having a cleft is about 5% (1 in 20). If a family has one parent with a cleft but no children with a cleft, the risk of their next child having a cleft is about 5% (1 in 20). If a family has no parent with a cleft but two children born with clefts, the risk of their next child having a cleft is about 10% (1 In 10). If a family has one parent and one child with a cleft, the risk of their next child having a cleft approaches 20% (1 in 5). In other words, a family with one parent and one child born with a cleft has a much higher chance of having a child with a cleft (1 in 5) than the average family (1 in 700), but this family still has an 80% (4 in 5) chance of their next child NOT being born with a cleft. So even when a parent and a child have had cleft lip and palate, the risk of the next child being born with a cleft is higher than the average person, but still relatively low.
There are rare exceptions to these inheritance patterns in which the parents have a higher risk of having a child with a cleft. For this reason, genetic testing should be done whenever there is a strong family history of cleft lip and/or palate. Van der Woude syndrome is a condition that demonstrates autosomal dominant inheritance of cleft lip and palate, where 50% of a family’s children may be born with a cleft. The characteristic feature of Van der Woude syndrome are lower lip pits. If you have a history of cleft lip and palate in your family with the association of lip pits you should have a consultation with a geneticist to assess for Van der Woude.
Mothers are naturally concerned if they did something to directly cause the cleft to occur. The maternal use of certain medications (phenytoin (Dilantin), other anticonvulsants or retinoic acid) and substances (maternal smoking or alcohol) are known to increase the risk of having a child with a cleft. However, the majority of children born with a cleft of the lip or palate have none of these associated factors.
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