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Important Facts for Birth Defects: Prevalence of Anencephaly per 10,000 Live Births


Anencephaly means an infant is born without a skull, with cerebral hemispheres completely missing or reduced to small masses attached to the base of the skull. Prevalence of anencephaly is the number of live-born infants with anencephaly per 10,000 live-born infants. (Live-born infants are infants born with any evidence of life.)


Number of live-born infants with anencephaly


Number of live-born infants

Data Interpretation Issues

In January 2000, birth defects became a reportable condition in New Mexico; however, birth defects were collected prior to this date. The first year of consistent data is 1998. For anencephaly data, the most recent year of analyzed data is 2011. Data are collected on live births occurring in-state to NM residents. Therefore, live births that occur in NM among out-of-state residents are excluded. Case finding/identification occurs through review of birth and death certificates, hospital discharge diagnoses, records from pediatric specialists and prenatal diagnostic providers. Birth defect cases are ascertained up to age 4; however, the majority of diagnoses are made by age 1.

Why Is This Important?

Birth defects pose a significant public health problem. One in 33 babies is born with a structural birth defect in the United States. Birth defects are a leading cause of infant mortality and are responsible for considerable morbidity and disability with enormous economic and social costs. Anencephaly is not compatible with life. Infants born with anencephaly die within a few days of birth. In 1992, the U.S. Public Health Service recommended that women of childbearing age increase consumption of the vitamin folic acid to reduce the number of spina bifida and anencephaly cases in the United States. By 1998, <30% of women were following this recommendation. In 2001, researchers from CDC determined that the overall birth prevalence of these two neural tube defects declined 19% after mandatory folic acid fortification.

Healthy People Objective: Reduce occurrence of anencephaly

U.S. Target: 22.1 live births and/or fetal deaths with anencephaly per 100,000 live births

Other Objectives

CDC Environmental Public Health Tracking, Nationally Consistent Data and Measures (EPHT NCDM)

How Do We Compare With the U.S.?

Before folic acid fortification, approximately 4,000 pregnancies resulted in 2,500--3,000 births in the United States each year affected by anencephaly or spina bifida.( During 1996--2001 in the US, 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 US prevalence of anencephaly from 2004-2006 was 2.06 per 10,000 births. For more information, please see: These data come from 14 birth defects surveillance programs: Arkansas, Arizona, California [8-county Central Valley], Colorado, Georgia [5-county metropolitan Atlanta], Illinois, Iowa, Kentucky, Massachusetts, North Carolina, Oklahoma, Puerto Rico, Texas, and Utah. Due to variability in the methods used by state birth defects surveillance systems and differences in populations and risk factors, state prevalence estimates may not be directly comparable with national estimates or those of other states.
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Content updated: Tue, 12 Aug 2014 11:49:04 MDT