Effects of folic acid fortification on spina bifida prevalence in Brazil

Abstract

To assess spina bifida birth prevalence changes after folic acid fortification of wheat and maize flours began in Brazil in June 2004. Cross-sectional study of Brazilian live births in 2004 and 2006. Spina bifida birth prevalence from the Live Births Information System (SINASC: Sistema de Informações sobre Nascidos Vivos) in a prefortified period was compared to a period fortified with folic acid in each state. Observed prevalence rates in 2004 were used to calculate the expected prevalence rates in 2006 under the null hypothesis that both were similar. The observed/expected (O/E) ratios were tested by two-tailed Z-test. To minimize ascertainment differences among states, the O/E ratio of each one of the 27 Brazilian states was adjusted for the number of births with the Mantel-Haenszel statistic. RESULTS The reduction in spina bifida birth prevalence in 2006 was 39% (O/E = 0.61; 95% confidence interval [CI], 0.55-0.67), and 40% (O/E = 0.60; 95% CI, 0.53-0.68), after adjusting for state birth number. This reduction was significant (p < 0.0001), and heterogeneous among states (χ(2) = 72.96; p < 0.0001). Using SINASC data, there was a significant reduction in spina bifida birth prevalence in Brazil, probably related to the folic acid food fortification program.