Updated Estimates of Neural Tube Defects Prevented by Mandatory Folic Acid Fortification

 

Jen­nifer Williams, et al. 

Mor­bid­i­ty and Mor­tal­i­ty Week­ly Report. 2015;64(1):1–5. 

In 1992, the U.S. Pub­lic Health Ser­vice rec­om­mend­ed that all women capa­ble of becom­ing preg­nant con­sume 400 μg of folic acid dai­ly to pre­vent neur­al tube defects (NTDs). NTDs are major birth defects of the brain and spine that occur ear­ly in preg­nan­cy as a result of improp­er clo­sure of the embry­on­ic neur­al tube, which can lead to death or vary­ing degrees of dis­abil­i­ty. The two most com­mon NTDs are anen­cephaly and spina bifi­da. Begin­ning in 1998, the Unit­ed States man­dat­ed for­ti­fi­ca­tion of enriched cere­al grain prod­ucts with 140 μg of folic acid per 100 g. Imme­di­ate­ly after manda­to­ry for­ti­fi­ca­tion, the birth preva­lence of NTD cas­es declined. For­ti­fi­ca­tion was esti­mat­ed to avert approx­i­mate­ly 1,000 NTD-affect­ed preg­nan­cies annu­al­ly. 

The birth preva­lences of spina bifi­da, anen­cephaly, and both NTDs com­bined were esti­mat­ed as the total num­ber of cas­es divid­ed by the total num­ber of live births dur­ing the pre-for­ti­fi­ca­tion (1995–1996) and post-for­ti­fi­ca­tion peri­ods (1999–2011). These preva­lence esti­mates were mul­ti­plied by the aver­age num­ber of live births in the Unit­ed States for the select­ed peri­ods to esti­mate the annu­al num­ber of NTD cas­es nation­wide. Preva­lence esti­mates were also cal­cu­lat­ed by type of sur­veil­lance pro­gram (i.e., pro­grams with pre­na­tal ascer­tain­ment and pro­grams with­out pre­na­tal ascer­tain­ment) and mater­nal race/ethnicity (i.e., non-His­pan­ic white, non-His­pan­ic black, and His­pan­ic). The esti­mat­ed annu­al num­ber of NTDs pre­vent­ed was cal­cu­lat­ed as the dif­fer­ence between the esti­mat­ed annu­al num­ber dur­ing the pre-for­ti­fi­ca­tion peri­od and the esti­mat­ed annu­al num­ber dur­ing the post-for­ti­fi­ca­tion peri­od using preva­lence esti­mates from pro­grams with pre­na­tal ascer­tain­ment.

A decline in NTDs was observed for all three of the racial/ethnic groups exam­ined between the pre-for­ti­fi­ca­tion and post-for­ti­fi­ca­tion peri­ods (Fig­ure). The post-for­ti­fi­ca­tion preva­lence has remained rel­a­tive­ly sta­ble. Dur­ing the observed peri­ods, His­pan­ics con­sis­tent­ly had a high­er preva­lence of NTDs com­pared with the oth­er racial/ethnic groups, where­as non-His­pan­ic blacks gen­er­al­ly had the low­est preva­lence.