Historical perspective on folic acid and challenges in estimating global prevalence of neural tube defects.

Neural tube defects (NTD) are major congenital malformations affecting births worldwide. NTD are associated with life-long disability, significant medical care costs, and child mortality. Their prevalence varies worldwide. We conducted a review of published literature and surveillance systems to examine challenges in estimating an overall global prevalence estimate for NTD. Our review showed that most low- and middle-income countries do not track NTD and indicate a high prevalence of these malformations where data are available. Challenges in global NTD prevalence estimation include (1) quality of surveillance methods, (2) existing risk factors (including geographic or socioeconomic factors, availability and use of folic acid, and racial-ethnic and genetic factors), and (3) limitations in education and access to care. We recommend population-based surveillance systems tracking all pregnancy outcomes and major risk factors. Countries should invest in sustainable, multisource surveillance systems, in parallel to folic acid interventions, for gaining a more accurate knowledge of global prevalence of NTD than we currently have. Such efforts will assist in both global prevention of NTD and periodic evaluation of folic acid interventions for NTD reduction. Global NTD prevalence data can drive political will and accelerate the implementation and evaluation of NTD prevention programs.