Genetic analysis of cleft lip and cleft palate in southern Poland. I. Empiric and relative recurrence risks.

The study covered 1009 families with CL +/- P and 490 families with CP coming from the region of southern Poland wherein the incidence is 1.3/1000 for CL +/- P and 0.51/1000 for CP. The empiric recurrence risk of CL +/- P and CP was 1.6% +/- 0.66 and 0.93% +/- 0.75, respectively. It was found that the risk of CL +/- P recurrence was three times greater among the sibs of male probands in comparison to that of female index cases. The relative risk of malformation recurrence in a family with one of the offspring already affected was 14.57 for CL +/- P and 19.85 for CP. The heritability values, calculated according to Falconer's formula were found to be 54.77% +/- 5.07 for CL +/- P and 52.79% +/- 8.63 for CP and suggested the significant effect of environmental factors on the etiology of these anomalies.