Increasing incidence of clefts in Finland: reliability of hospital records and central register of congenital malformations.

The treatment of cleft lip and/or palate [CL(P), CP] in Finland has been centralized to one unit since 1947. Since 1963 all congenital malformations are reported to a central register. Comparison of these two materials showed that altogether 3928 children with clefts, born from 1948 to 1975, were registered in a total of 2 258 850 live born children in Finland, corresponding an incidence of 1.74%. There was a constant registered rise in the incidence from 1.31% in 1948-52 to 2.16% in 1969-75, indicating a corrected "true" increase in the incidence by 33% in 28 years, or approximately by over one percent per year. Of all registered clefts born 1963-75 23.5% were lacking from the Register of Congenital Malformations, and 10.3% from the hospital records. In 1948-75 55.8% of the clefts belonged to the group CP and 44.2% to CL(P). The incidence of CP increased from 0.78% in 1948-52 to 1.21% in 1969-75, and that of CL(P) from 0.53 to 0.95%. An average of 13,8% of the CP-cases were submucous clefts. Their registered incidence in all live born children increased from 0.08% in 1948-52 to 0.19% in 1969-75.