Background/Purpose. Studies have indicated that increased parental age may be one of several predisposing factors for development of cleft lip and palate. The aim of the present study was to investigate the parental age in relation to severity of cleft diagnosis in a Danish population study of cleft individuals, as well as to compare parental age in the cleft population with normative values of parental age. It was hypothesized that there was no difference in parental age between the cleft groups with incomplete and complete clefts, respectively.

Methods/Descriptions. The consecutive non-syndromic cleft sample comprised 678 individuals (equal to the number of individuals born with a cleft in Denmark during a 6-year period). In 608 cases maternal and paternal age were recorded, and of these cases 285 were firstborns; 71 had a Complete Cleft Lip and/or Palate (CC) and 192 had an Incomplete Cleft Lip and/or Palate (IC). Wilcoxon Rank-Sum test (5% significance level) was applied in order to test for group differences. Standard logistic regression was used in order to estimate the risk of developing CC relative to IC.

Results. In the group with CC mean paternal age was 29.5+/-4.5 (1SD) years and mean maternal age was 25.4+/-3.8 years. In the group with IC mean paternal age was 27.0+/-6.1 years and mean maternal age was 24.1+/-4.7 years. Both paternal and maternal age was significantly higher in the group with CC than in the group with IC (p(paternal)=0.001; p(maternal)=0.022). The mean parental ages in the group with IC did not differ from normative population values during the same time period. Logistic regression showed for paternal age OR=1.1[1.04,1.16](Wald confidence limits); for maternal age 1.08[1.01,1.15].

Conclusions. The hypothesis was rejected. Parental age was significantly higher in the group with CC than in the group with IC, where the parental age was comparable to normative values. Increased parental age seems to be a risk factor for CC in the off-spring with an increased risk of having a CC (compared to IC) of 10% per year of increase in paternal age, and 8% per year of increase in maternal age.