Most of the causes are unknown, some are due to environmental or inheriting factors…
A. Environmental factors
- Viral infection – e.g. German measles.
- Drug effect – e.g. Anti-convulsion, cytotoxic drugs, steroid etc.
- Exposure to X-ray radiation during pregnancy
- Nutritional inbalance – caused by repeated vomiting and poor appetite during pregnancy.
B. Inheriting factors
Formed by abnormal factors, cells or chromosomes. . If one of the parents is a cleft lip/palate patient, or the parents have on affected child, the occurrence ratio could be as high as 1:20; if both parents are cleft patients or they already have two affected children, the occurrence ration is 1:4.