Changing lifestyles and oral clefts occurrence in Denmark

Abstract

Objective: The aim of this project was to assess whether any changes in the birth prevalence of cleft lip with/without cleft palate (CL[P]) occurred in Denmark during the period 1988 through 2001. In this period an official recommendation of a supplementation of folic acid to pregnant women was introduced; furthermore, smoking among pregnant women decreased considerably.

Design and settings: There are few places in which ecological studies of oral clefts are possible. Denmark provides a particularly good setting for this kind of study because of a high ascertainment and a centralized registration of subjects with cleft over the last 65 years.

Participants: Cleft occurrence in Denmark from 1936 to 1987 has previously been reported. Here we extend the study to include all live-born children with oral clefts born in Denmark in 1988 through 2001. Among a total of 992,727 live births, 1332 children with CL(P) were born during this period.

Results and conclusions: The birth prevalence of CL(P) in Denmark has previously been found to be constant in the period 1962 through 1987, with a frequency of 1.4 to 1.5 per 1000 live births. This study showed a similar occurrence in 1988 through 2001 (birth prevalence = 1.44 per 1000 live births, 95% confidence interval = 1.37 to 1.52). The introduction of folic acid and the decrease in smoking prevalence among pregnant women do not seem to have reduced the birth prevalence. This may be due to noncompliance with the folic acid recommendation and/or only a weak causal association between folic acid and smoking and occurrence of CL(P).

FIGURE 1

Smoothed prevalence (5-year moving average) of subgroups of cleft lip with/without cleft palate per 1000 live births in Denmark during 1962 through 2001. The vertical line indicates the beginning of the update period, January 1988. (all,———; nonsyndromic,–··–; male,– – –; female,— — —).

FIGURE 2

Overall birth prevalence of cleft lip with/without cleft palate per 1000 live births in Denmark during 1962 through 2001 with fitted regression line. The vertical line indicates the beginning of the update period, January 1988.