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The exact cause of cleft lip and cleft palate is not completely understood. Cleft lip and/or cleft palate are caused by multiple genes inherited from both parents, as well as environmental factors that scientists do not yet fully understand.
When a combination of genes and environmental factors cause a condition, the inheritance is called "multifactorial" (many factors contribute to the cause). Because genes are involved, the chance for a cleft lip and/or cleft palate to happen again in a family is increased, depending on how many people in the family have a cleft lip and/or cleft palate.
If parents without clefts have a baby with a cleft, the chance for them to have another baby with a cleft ranges from 2 to 8 percent. If a parent has a cleft, but no children have a cleft, the chance to have a baby with a cleft is 4 to 6 percent. If a parent and a child have a cleft, the chance is even greater for a future child to be born with a cleft. Genetic consultation is suggested.