Epidemiology of orofacial clefts in Finland: a review.

Epidemiological studies on clefts in Finland seem to give support to the following theories: 1. Both genetic and environmental factors seem to play a role in the pathogenesis of cleft lip and/or cleft palate, which in the majority of cases are probably two different anomalies. 2. The incidence of cleft lip and/or cleft palate in Finland has increased, probably because of a change in the environmental factors. 3. The incidence of cleft palate in Finland is higher than anywhere, which seems to be the result of differing genetic factors. 4. The exogenous factors remain unidentified, but in cleft lip and/or cleft palate parallel fluctuations and an increasing trend have been noticed, arguing for similar and simultaneous factors. 5. More patients with cleft palate than cleft lip/palate have "cleft syndromes."