How Cleft Lip and Cleft Palate Occurs

Cleft Lip and Cleft Palate Have Genetic and Environmental Risk Factors

Cleft Lip
Cleft Lip. Photo © A.D.A.M.

Cleft lip and palate occur due to a combination of both genetic and environmental factors (multifactorial inheritance). They are types of congenital malformation. All factors that lead to the potential for cleft lip and palate are associated with the embryonic stage of development (the first 3 to 8 weeks of pregnancy).

During this stage, the vital organs and external features begin forming. Under normal circumstances, the tongue drops back and the palates of the mouth are able to fuse together.

But in cases of this malformation, the structures of the face are allowed to develop without the restrictions that a fully encircled mouth causes. The clefts are unable to fuse normally, and cleft lip and/or cleft palate occur.

Risk Factors For Cleft Lip and Cleft Palate To Occur

Genetic Factors

A family history of cleft lip and cleft palate can increase the chances of passing the birth defect on. If the mother or father has a cleft lip or palate, a genetic counselor can be consulted to discuss chances of passing this on to future children. If you and a previous child both have had a cleft lip or palate, the chances of having future children with cleft lip and palate increases.

Though genetics can play a role in the development of clefts, 85% are not part of a known genetic syndrome.

To break down a child's risk of a cleft lip with or without cleft palate when no known genetic syndrome is at play:

  • Parent has cleft: 2%
  • Sibling has cleft: 4 to 7%
  • Two siblings have cleft: 10%
  • Parent and sibling have cleft: 11 to 14%

Environmental Factors

Teratogens (substances that can cause birth defects) such as using tobacco while you are pregnant, drinking alcohol, or using illegal or certain prescription drugs, can cause birth defects such as cleft lip and cleft palate.

The most critical time for the development of the lip and palate begins around 7 weeks and lasts until 9 to 12 weeks of pregnancy. The development of the lip and palate are separate events, so one malformation does not mean the other will be occur -- even though both cleft lip and palate frequently occur together.

In order to minimize the environmental factors, your obstetrician can be consulted to discuss medications and habits that may have teratogenic effects on your baby. Stay away from smoking and inhaling secondary smoke, as some medical doctors estimate that 11 to 12% of cleft lip or palate cases may be related to smoking.


McCance, K.L. & Huether, S.E. (1994). Pathophysiology: The Biologic Basis for Disease in Adults and Children (Third Edition). St. Louis: Mosby.

"Risk of idiopathic cleft lip with or without cleft palate and cleft palate alone in a child of an affected family." UpToDate. Accessed: September 2009 from

Wong, D.L., Perry, S.E. & Hockenberry, M.J. (2002). Maternal Child Nursing Care (Second Edition). St. Louis: Mosby.

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