Trends in the prevalence of congenital heart disease: comprehensive observations over a 24-year period in a defined region of Canada.

Objective: To determine the prevalence of congenital heart disease (CHD) in the three Maritime provinces, and to study prevalence differences among provinces and defined regions within these provinces.
Design: Each province was divided by counties into regions. All cases of CHD who were born alive in the study area between 1966 and 1989 were entered in a registry. Prevalences were analyzed for each province and for selected regions per year, per 1000 live births, and by diagnosis made by one year of age and by the 16th birthday. Comparison was then made with prevalences of a group who had severe lesions.
Interventions: Excepting a small number of CHD cases who were diagnosed by autopsy only, diagnosis was made by pediatric cardiologists using appropriate procedures, including cardiac ultrasound and cardiac catheterization.
Setting: The only tertiary care centre for children's heart disease in the provinces of Nova Scotia, New Brunswick and Prince Edward Island, areas of relative geographic isolation (combined population of 1.75 million people).
Main Results: A statistically significant positive linear trend occurred in these provinces during the study. The recorded prevalence of CHD in New Brunswick was significantly lower. Pooled prevalences by the first and 16th birthdays (8.0 and 12.5 per 1000 live births, respectively) of two regions of highest prevalence for 1980-86 were significantly higher (P < 0.05) than the pooled prevalence rate of all the remaining regions. Prevalence rates of a group with severe lesions were stable for 1976-86 in all regions.
Conclusions: Differences in prevalence of CHD among provinces and regions were related to ascertainment levels. Prevalence of CHD with diagnosis by the first and 16th birthdays were approximately 8.0 and 12.5 per 1000 live births, respectively. The prevalence rate of a severe lesion group was a stable measure.