Cleft lip and palate happen when the baby’s upper lip and/or the roof of the mouth do not fuse completely in early pregnancy, usually due to a mix of genetic and environmental factors. In most cases, there is no single “fault” or obvious cause, but rather several small risks adding up during weeks 4–10 of gestation.

How cleft lip and palate form

During early pregnancy, separate facial structures grow toward each other and are supposed to join to form the upper lip and palate. If this fusion is interrupted or incomplete, a gap (cleft) remains in the lip, the palate, or both.

Key points:

  • Cleft lip happens when the tissues that form the upper lip do not fully join.
  • Cleft palate happens when the roof of the mouth (hard and/or soft palate) does not close completely.
  • These are among the most common birth differences affecting the face and mouth worldwide.

Genetic causes

Genetics play a major role in many cleft cases.

  • Multiple genes are usually involved (multifactorial inheritance), not just a single “cleft gene.”
  • Clefting can run in families, and having a close relative with a cleft increases the chance in future pregnancies.
  • Around 20–50% of cleft lip/palate cases are thought to be mainly genetic, sometimes part of known syndromes (for example Van der Woude syndrome involving the IRF6 gene).
  • Clefts can also occur as one feature of broader genetic syndromes (more than 400 syndromes have been linked with clefts, such as Pierre Robin sequence and some forms of Down syndrome).

Environmental and pregnancy-related factors

Even with genetic susceptibility, environmental or pregnancy factors can influence whether a cleft actually forms.

Factors that have been associated (not guaranteed causes) include:

  • Maternal smoking or alcohol use in early pregnancy.
  • Certain medications in early pregnancy , especially some anti-seizure/anticonvulsant drugs and retinoids (vitamin A–related drugs) linked with birth defects.
  • Poor folic acid intake or nutritional deficiencies before and during early pregnancy.
  • Maternal obesity and some chronic illnesses may slightly raise risk.
  • Exposure to potential teratogens such as pesticides, organic solvents, lead, or high-dose vitamin A; and illicit drugs like cocaine have been reported in studies.
  • Experimental work also suggests that low oxygen (hypoxia) early in pregnancy can contribute in animals.

These do not guarantee a cleft will occur; they seem to shift the odds, especially when combined with genetic vulnerability.

Important clarifications and myths

  • In many babies with cleft lip and/or palate, the exact trigger is never identified.
  • Everyday things like minor bumps, stress, or typical colds during pregnancy are not known to directly cause clefts.
  • Parents do not “cause” a cleft by anything they consciously do; it is usually a complex mix of unseen genetic and environmental influences.

Can cleft lip and palate be prevented?

Risk cannot be completely eliminated, but some steps can lower overall risk of birth defects, including clefts:

  1. Take folic acid as recommended before conception and in early pregnancy.
  1. Avoid smoking, alcohol, and non‑essential drugs in pregnancy.
  1. Review prescription medicines with a healthcare provider when planning pregnancy.
  1. Aim for a healthy weight and good nutrition before and during pregnancy.

Information gathered from public forums or data available on the internet and portrayed here.