Spina bifida and anencephaly prevalence--United States, 1991-2001.

Spina bifida and anencephaly are serious birth defects. To reduce the occurrence of these birth defects, the Food and Drug Administration authorized the fortification of all enriched cereal grain products with folic acid in March 1996, with compliance mandatory by January 1998. This report reviews data reported to CDC's National Center for Health Statistics (NCHS) regarding spina bifida and anencephaly prevalence for live births in the United States during 1991-2001. Since 1989, NCHS has compiled birth defect data from checkboxes that appear on birth certificates. For consistency in trends, this report uses data for 1991-2001 from all U.S. reporting areas except Maryland, New Mexico, and New York. Data for 2001 are preliminary. During 1996-2001, a 23% decline occurred in neural tube defects (spina bifida and anencephaly combined). Spina bifida declined 24% during this period, and anencephaly declined 21%. The United States has experienced declines in spina bifida and anencephaly cases since folic acid fortification of all enriched cereal grain products. The observed declines have translated into approximately 920 infants being born without these serious defects each year. Continued monitoring of the occurrence of spina bifida and anencephaly will be necessary to evaluate the effectiveness of folic acid fortification.