Long term trends in prevalence of neural tube defects in Europe: population based study.

STUDY QUESTION: What are the long term trends in the total (live births, fetal deaths, and terminations of pregnancy for fetal anomaly) and live birth prevalence of neural tube defects (NTD) in Europe, where many countries have issued recommendations for folic acid supplementation but a policy for mandatory folic acid fortification of food does not exist? METHODS: This was a population based, observational study using data on 11,353 cases of NTD not associated with chromosomal anomalies, including 4162 cases of anencephaly and 5776 cases of spina bifida from 28 EUROCAT (European Surveillance of Congenital Anomalies) registries covering approximately 12.5 million births in 19 countries between 1991 and 2011. The main outcome measures were total and live birth prevalence of NTD, as well as anencephaly and spina bifida, with time trends analysed using random effects Poisson regression models to account for heterogeneities across registries and splines to model non-linear time trends. SUMMARY ANSWER AND LIMITATIONS: Overall, the pooled total prevalence of NTD during the study period was 9.1 per 10,000 births. Prevalence of NTD fluctuated slightly but without an obvious downward trend, with the final estimate of the pooled total prevalence of NTD in 2011 similar to that in 1991. Estimates from Poisson models that took registry heterogeneities into account showed an annual increase of 4% (prevalence ratio 1.04, 95% confidence interval 1.01 to 1.07) in 1995-99 and a decrease of 3% per year in 1999-2003 (0.97, 0.95 to 0.99), with stable rates thereafter. The trend patterns for anencephaly and spina bifida were similar, but neither anomaly decreased substantially over time. The live birth prevalence of NTD generally decreased, especially for anencephaly. Registration problems or other data artefacts cannot be excluded as a partial explanation of the observed trends (or lack thereof) in the prevalence of NTD. WHAT THIS STUDY ADDS: In the absence of mandatory fortification, the prevalence of NTD has not decreased in Europe despite longstanding recommendations aimed at promoting peri-conceptional folic acid supplementation and existence of voluntary folic acid fortification. FUNDING, COMPETING INTERESTS, DATA SHARING: The study was funded by the European Public Health Commission, EUROCAT Joint Action 2011-2013. HD and ML received support from the European Commission DG Sanco during the conduct of this study. No additional data available.

Neural tube defects in Australia: trends in encephaloceles and other neural tube defects before and after promotion of folic acid supplementation and voluntary food fortification.

BACKGROUND: Use of periconceptional folic acid supplementation has been promoted in Western Australia since late 1992, and voluntary fortification of some foods with folic acid has been permitted in Australia since 1996. Reduced rates of neural tube defects (NTDs) have been observed since 1995. Aboriginal infants have a higher rate of NTDs, but no fall in rates has been documented. Encephaloceles have not been examined separately. METHODS: Data on anencephaly, spina bifida, and encephalocele were obtained from the Western Australian Birth Defects Registry. The prevalence ratio for each type of NTD was calculated, comparing 1993 to 1995 (promotion of supplements, no fortification) and 1996 to 2006 (promotion of supplements and voluntary fortification) with 1980 to 1992 (no promotion or fortification). RESULTS: From 1996 to 2006, there was a 32% reduction in anencephaly, 23% in spina bifida, and 34% in encephalocele compared with 1980 to 1992. There were no differences seen from 1993 to 1995 compared with 1980 to 1992. For Aboriginal infants, the rates were higher than for non-Aboriginal infants, for each type of NTD. The prevalence ratios, comparing 1996 to 2006 with 1980 to 1995, were 0.70 (CI, 0.61-0.79) for non-Aboriginal infants and 0.90 (CI, 0.61-1.32) for Aboriginal infants. CONCLUSIONS: Overall, the rates of encephalocele, anencephaly, and spina bifida have fallen to a similar extent in association with promotion of folic acid supplements and voluntary fortification. No such falls were seen for Aboriginal infants. These data will provide a useful baseline against which to monitor the effects of mandatory fortification on NTDs when it is introduced in Australia in September 2009.