Spina Bifida Incidence at Birth -- United States, 1983-1990

Spina bifida, a birth defect of the spinal column that can cause varying degrees of paralysis, is a major contributor to serious developmental disabilities in the United States. To determine the incidence and descriptive epidemiology of spina bifida, CDC analyzed reports from 16 states with population-based birth defects surveillance systems (Table 1). This report summarizes findings from this analysis for 1983-1990.

Of the 16 state-based birth defects surveillance systems, 13 systems are statewide in coverage (exceptions: Arkansas, California, and Georgia). All but one (Georgia (1)) of the state-based birth defects surveillance systems are operated by the state health department or by a state university. These 16 states account for approximately 23.5% of the total U.S. population.

All live-born and stillborn infants with spina bifida * were included in the analysis; however, in three states data were not available on cases involving stillborn infants. Nine state surveillance systems (Colorado, Illinois, Maryland, Missouri, Nebraska, New Jersey, New York, North Carolina, and Virginia) identified cases from reports submitted by physicians and staffs of hospitals, clinics, or other health-care facilities; seven states (Arizona, Arkansas, California, Georgia, Hawaii, Iowa, and Washington) used trained surveillance staff to identify cases by systematic review of medical and other records from hospitals, clinics, and other health-care facilities. Spina bifida incidence rates were determined for each state during the surveillance period; however, the specific surveillance periods during 1983-1990 varied by state (Table 1). The states were grouped into the four U.S. census regions: Northeast, North Central, South, and West.

From 1983 through 1990, the spina bifida incidence rate for these 16 states was 4.6 cases per 10,000 births; during this period, the annual rate declined from a peak of 5.9 cases per 10,000 births in 1984 to 3.2 cases per 10,000 births in 1990 (Figure 1). Although rates were similar by region, state-specific rates varied substantially (range: 3.0 (Washington) to 7.8 (Arkansas)). Rates also varied among racial/ethnic groups (Table 1) and were lowest for Asians/Pacific Islanders (2.3) and highest for Hispanics (6.0). The rate for Hispanics declined substantially from 1983 to 1990, and the rate for blacks was stable after 1984 (Figure 1). In 1990, spina bifida rates for whites, blacks, and Hispanics were nearly identical.

Reported by: T Flood, MD, Office of Chronic Disease Epidemiology, Arizona Dept of Health Svcs. M Brewster, PhD, Arkansas Reproductive Health Monitoring System, Arkansas Children's Hospital, Little Rock, Arkansas. J Harris, MD, California Birth Defects Monitoring Program, California Dept of Health Svcs. S Keefer, MS, Colorado Registry for Children with Special Needs, Colorado Dept of Health. R Merz, MS, Hawaii Birth Defects Monitoring Program, Hawaii Dept of Health. H Howe, PhD, Div of Epidemiologic Studies, Illinois Dept of Public Health. J Hanson, MD, State Health Registry of Iowa, Iowa City. S Panny, MD, Div of Hereditary Disorders, Maryland State Dept of Health and Mental Hygiene. J Bakewell, Bur of Health Data Analysis, Missouri Dept of Health. M Seeland, Health Data Support Div, Nebraska State Dept of Health. P Costa, MA, Birth Defects Registry, New Jersey State Dept of Health. C Olsen, PhD, Bur of Environmental Epidemiology and Occupational Health, New York State Dept of Health. A Murray, MA, State Center for Health and Environmental Statistics, North Carolina Dept of Environment, Health, and Natural Resources. M Marazita, PhD, Dept of Human Genetics, Medical College of Virginia, Virginia Commonwealth Univ, Richmond; Virginia Dept of Health. C Hill, Birth Defects Registry, Washington Dept of Health. Birth Defects and Genetic Diseases Br, Div of Birth Defects and Developmental Disabilities, National Center for Environmental Health and Injury Control, CDC.

Editorial Note

Editorial Note: The public health impact of spina bifida in the United States is substantial: each year, approximately 1500 infants are born with spina bifida (2), and the annual medical and surgical costs (based on 1985 dollars) for persons with spina bifida exceed $200 million (2). The findings in this report are the first to describe the use of multiple state systems for characterizing the birth incidence of a major preventable birth defect for these reporting states.

Public health and health-care providers require accurate determinations of spina bifida rates to evaluate the effectiveness of programs to reduce the incidence of this problem in the United States. Until recently, the only source of ongoing information about the national birth incidence of spina bifida was CDC's national Birth Defects Monitoring Program (BDMP), a hospital-based surveillance system that obtains information about birth defects in newborns from discharge abstracts in participating hospitals (1). The state-based birth defects surveillance systems described in this report are an additional source of information on the incidence of birth defects. Data from the state systems are population-based rather than hospital-based and provide more information on spina bifida cases in individual states than does the BDMP. Even though the findings in this report were computed for only 16 states, the combined state rate (4.6 per 10,000 live births) for 1983-1990 was nearly identical to the mean BDMP rate for 1983-1990 (4.4).

Potential explanations for the decline in spina bifida incidence rates, indicated by state surveillance, may be related to improved nutrition or other environmental factors (3). Prenatal diagnosis of affected pregnancies during the 1980s may have had an impact, but the relative impact on the decline is unknown. Differences in rates among racial/ethnic groups may be related to differences in genetic susceptibility to spina bifida, cultural dietary practices, or differences in other unidentified risk factors.

Findings from a recently published randomized controlled trial demonstrated that periconceptional supplementation with 4.0 mg of folic acid daily would prevent 70% of the recurrence of neural tube defects (NTDs) among women who had a prior NTD-affected pregnancy (4). In August 1991, CDC published interim recommendations for folic acid supplementation for women who have had an infant or fetus with spina bifida, anencephaly, or encephalocele (5).

State-based surveillance systems provide important information regarding the incidence of birth defects in individual states and may be used by states to estimate the number of seriously malformed infants that will be born each year and to plan for the provision of health services for these infants. CDC will collaborate with state and local health agencies in using these surveillance data to refine further epidemiologic characteristics of spina bifida. Further efforts to prevent spina bifida and other NTDs should also focus on pregnancies of women who have not had previous NTD-affected pregnancies.

On July 27, 1992, CDC will convene a meeting in Atlanta to consider a proposal that all women in the United States who are capable of becoming pregnant should consume 0.4 mg of folic acid per day to prevent spina bifida and other neural tube defects. Additional information about this meeting is available from the Chief, Birth Defects and Genetic Diseases Branch, Division of Birth Defects and Developmental Disabilities, National Center for Environmental Health and Injury Control, CDC, Mailstop F-45, 1600 Clifton Road, NE, Atlanta, GA 30333; telephone (404) 488-7160.

References

1. Edmonds LD, Layde PM, James LM, Flynt JW, Erickson JD, Oakley GP Jr. Congenital malformations surveillance: two American systems. Int J Epidemiol 1981;10:247-52.

2. CDC. Economic burden of spina bifida -- United States, 1980-1990. MMWR 1989;38:264-7.

3. Yen IH, Khoury MJ, Erickson JD, et al. The changing epidemiology of neural tube defects, United States, 1968-1989. Am J Dis Child (in press).

4. MRC Vitamin Study Research Group. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. Lancet 1991;338:131-7.

5. CDC. Use of folic acid for prevention of spina bifida and other neural tube defects -- 1983-1991. MMWR 1991;40:513-6.

• Defined as International Classification of Diseases, Ninth Revision, code 741.

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