Birth Prevalence of Congenital Heart Disease

To the Editor: We were interested to read the interpretation by Prsa et al1 of a decline in prevalence of severe congenital heart disease (CHD) in Quebec since 1998, following folic acid fortification. We examined EUROCAT data on severe CHD from 1990 to 2006 (Figure), which include terminations of pregnancy for fetal anomaly as well as live births, and fetal deaths from 20 weeks' gestation. These data are based on 14 population-based registries in 11 countries of Europe covering a population of 3,614,371 births 1990–2006, all of whom contributed to a recent report on CHD prevalence in Europe for the period 2000–2005.2 Data for individual registries can be accessed at http://www.eurocat.ulster.ac.uk/pubdata/tables.html. In this study, severe CHD includes single ventricle, hypoplastic left heart, hypoplastic right heart, Ebstein malformation, tricuspid atresia, pulmonary valve atresia, common arterial truncus, atrioventricular septal defects, aortic valve atresia/stenosis, transposition of great vessels, tetralogy of fallot, total anomalous pulmonary venous return, and coarctation of aorta. Cases with a chromosomal anomaly are excluded.FIGURE.: Prevalence of severe nonchromosomal congenital heart defects, and of neural tube defects, per 1000 births, 14 EUROCAT registries 1990–2006. LB indicates live birth; TOPFA, terminations of pregnancy for fetal anomaly; and FD, fetal death.We see a rise in prevalence from 1990 to 2000, followed by a decline. If one applies a χ2 test for trend across the years, the decline is highly significant whether one tests this starting from 1998, as in the Quebec report, or 2000, as suggested by the data (test for trend P < 0.001). Further statistical analysis of trends, considering also different CHD subgroups within the general “severe” classification, is ongoing. Prsa et al1 also found a rise in the period 1993–1996, consistent with our data. The prevalence of terminations of pregnancy for CHD rose until 2000 and then stabilized (as shown in the Figure). This supports the Quebec researchers' judgement that the recent decline in livebirth prevalence is probably not explained by an increase in terminations of pregnancy. However, Prsa et al seem to have included liveborn children with CHD associated with Down syndrome and other chromosomal anomalies, the numbers of whom are more affected by terminations of pregnancy. Lack of terminations in the Quebec data also would have led to an underestimate of the rise in prevalence between 1993 and 1996. In Europe, there is no mandatory fortification of food with folic acid. There is some voluntary food fortification but no systematic information as to how this is affecting periconceptional folate status. Policies regarding folic acid supplementation have not been successful at reaching the majority of women preconceptionally in European countries3,4—some countries having rates below 10%, and the most active areas struggling to reach 50%. In the first decade after supplementation policies started to be introduced, there was no overall decline in neural tube defects (NTDs) prevalence in Europe,3,4 other than a continuation of a pre-existing decline in the United Kingdom and Ireland. However, in more recent years, there is some evidence of a decline in NTD in Europe (see the Figure, P < 0.01 for χ2 since 2000), though more shallow than that for CHD. Most European surveys find that more women start supplementation in early pregnancy than preconceptionally. It is possible that starting supplementation early in pregnancy is more successful in preventing CHD, with a slightly later critical period of development, than in preventing NTD, thus explaining the stronger decline of CHD than NTD in Europe. Nevertheless, a full explanation would require some consideration of why severe CHD prevalence rose prior to 2000, before falling. While relating the severe CHD decline to folic acid, whether by mandatory fortification or supplementation, is an interesting hypothesis, alternative interpretations should also be sought. Helen Dolk Maria A. Loane EUROCAT Central Registry University of Ulster United Kingdom [email protected] Lenore Abramsky Northwest Thames Congenital Malformation Register Northwick Park Hospital NHS Trust United Kingdom Hermien de Walle Department of Medical Genetics University Medical Centre Groningen The Netherlands Ester Garne Paediatric Department Hospital Liuebaelt Kolding, Denmark

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