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Trends in Spina Bifida and Anencephalus in the
United States, 1991-1999

In 1992 the U.S. Public Health Service recommended that women of childbearing age increase consumption of the vitamin folic acid to reduce spina bifida and anencephalus. In 1996 the U.S. Food and Drug Administration mandated that all enriched cereal grain products be fortified with folic acid no later than January 1998.  Recently the 1999 National Health and Nutrition Examination Survey released results showing that these public health actions have been effective in increasing folate status among U.S. women of childbearing age (MMWR, October 27, 2000).

Birth certificate data in the United States have been available for selected birth defects since 1989.  This Health E-Stat provides a 9-year trend for two neural tube defects, spina bifida and anencephalus.  Links to tables and figures are available below.

The rate of spina bifida in 1999 was 20.83 per 100,000 live births.  The rate has declined significantly between 1995 and 1999.  In 1999, 735 cases of spina bifida were reported.

After a decline in the early part of the decade, the anencephalus rate has been stable since 1994.  The rate of anencephalus in 1999 was 10.57 per 100,000 live births.  There were 373 reports of anencephalus in 1999.

Birth certificate data for 1991-98 are final, but data for 1999 are preliminary.  The preliminary birth data used here are 97.6% complete.  For further information about the preliminary birth data file see Births: Preliminary Data for 1999.  The numbers and rates for all years exclude data for Maryland, New Mexico, and New York, which in various years had either incomplete reporting or did not report these neural tube defects.   Both spina bifida and anencephalus are considered underreported on the birth certificate.  CDC is continuing to monitor and analyze neural tube defect occurrence data.

This page last reviewed January 11, 2007