Which of the following shows lowest frequency of cleft
lip and palate?
The incidence of cleft lip and palate is 1:600 live births and of isolated cleft palate is 1:1000 live births. The incidence increases  in  Oriental  groups  (1:500)  and  decreases  in  the black  population  (1:2000).  The  highest  incidence  reported for cleft lip and palate occurs in the Indian tribes of Montana, USA (1:276).
Although cleft lip and palate is an extremely diverse and variable  congenital  abnormality,  several  distinct  subgroups exist, namely cleft lip with/without cleft palate (CL/P), cleft palate (CP) alone and submucous cleft palate (SMCP).

The typical distribution of cleft types is:

Cleft lip alone: 15%;
Cleft lip and palate: 45%;
Isolated cleft palate: 40%.

Cleft lip/palate predominates in males, whereas cleft palate alone appears to be more common in females. In unilateral cleft lip the deformity affects the left side in 60% of cases.
Key Concept:
The incidence increases  in  Oriental  groups  (1:500)  and  decreases  in  the black  population (1:2000). The  highest  incidence  reported for cleft lip and palate occurs in the Indian tribes of Montana, USA (1:276).
Reference: Bailey & Love’s short practice of surgery , 27th  ed page no 688
Negroes
Afghanese
American Indian
Indian