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Prevalence of Neural Tube Defects and Folic Acid Knowledge and Consumption --- Puerto Rico, 1996--2006

Birth defects are one of the leading causes of infant mortality in both the mainland United States (1) and Puerto Rico (2). Neural tube defects (NTDs) are serious birth defects of the spine and brain; two of the most common NTDs are spina bifida and anencephaly. In the United States, NTD prevalence is higher among Hispanic women than among non-Hispanic white or non-Hispanic black women (3). In Puerto Rico, where most residents are Hispanic, the prevalence of NTDs (8.68 per 10,000 live births [4]) is higher than in the mainland United States (5.59 [5]). Consumption of folic acid before and during early pregnancy can prevent NTDs. To assess trends in NTD prevalence and prevalence of knowledge and consumption of folic acid supplements in Puerto Rico, data were analyzed from the Birth Defects Surveillance System (BDSS) for 1996--2005 and the Behavioral Risk Factor Surveillance System (BRFSS) for 1997--2006. This report describes the results of those analyses, which indicated that prevalence of folic acid knowledge and consumption among women of childbearing age increased from 1997 to 2003 but decreased from 2003 to 2006. During similar periods, NTD prevalence declined from 1996 to 2003 but did not change significantly from 2003 to 2005. To resume the decline in prevalence of NTDs, additional measures might be needed to increase folic acid supplement use among Puerto Rican women of childbearing age.

BDSS is a population-based, active surveillance system that assesses approximately 50,000 births in Puerto Rico each year; the most recent available data are from 2005. BDSS records abstractors conduct weekly visits to all birthing hospitals and read medical logs for neonatal intensive care units, pediatric units, delivery rooms, pathology laboratories, and clinics for infants at high risk. Abstractors also visit clinics for children with special health-care needs and pediatric cardiology offices. BDSS staff members review and code case information and perform annual record cross-checks and linkages with vital statistics databases in Puerto Rico. Data from BDSS and vital statistics records are used to calculate total annual NTD prevalence as the number of spina bifida or anencephaly cases (including live births, fetal deaths, stillbirths, spontaneous abortions, and elective terminations) per year, multiplied by 10,000 and then divided by the number of live births for each year.

BRFSS is an ongoing, random-digit--dialed telephone survey of the noninstitutionalized civilian population aged >18 years. BRFSS data files are weighted to the respondent's probability of being selected and to the age-, race-, and sex-specific populations from the annually adjusted census for Puerto Rico. To assess folic acid knowledge and daily folic acid consumption among nonpregnant women aged 18--44 years in Puerto Rico, data were collected from the surveys administered in 1997, 1998, 2000, 2002, 2003, 2004, and 2006; no folic acid questions were included in the 1999, 2001, and 2005 surveys. The total number of women surveyed during the 7 years of surveys was 6,356. Consumption was defined as reported daily consumption of a vitamin pill or supplement containing folic acid.* Knowledge was defined as knowing that folic acid consumption is recommended by certain health experts for the prevention of birth defects. Statistical estimates were weighted to reflect the total population of women aged 18--44 years in Puerto Rico. During 1996--2006, the BRFSS response rate§ in Puerto Rico ranged from 67%--81%, based on Council of American Survey and Research Organizations (CASRO) guidelines. Differences in data points were considered statistically significant at p<0.05 by chi-square test.

The annual number and prevalence of NTDs (i.e., spina bifida and anencephaly) in Puerto Rico declined significantly (p<0.05) from 93 (14.7 per 10,000 live births) in 1996 to 27 (5.3 per 10,000) in 2003 (Figure). From the 2003 levels, the number and prevalence of NTDs did not change significantly in 2004 (40 [7.8 per 10,000]) or 2005 (44 [8.7 per 10,000]). During a similar period, the estimated prevalence of folic acid supplement consumption among nonpregnant women aged 18--44 years increased significantly from 20.2% in 1997 to 30.9% in 2003, then decreased to 24.8% in 2006 (Figure, Table 1). Similarly, the estimated prevalence of knowledge of folic acid increased from 22.4% in 1997 to 72.0% in 2003, then decreased to 56.5% in 2006 (Table 2).

In 2006, statistically significant differences in reported knowledge of folic acid and folic acid supplement consumption were observed by age group, education, and household income. Among age groups, a greater percentage of women aged 25--34 years (63.6%) reported knowledge of folic acid than women aged 35--44 years (50.8%). However, a greater percentage of women aged 35--44 years (28.6%) reported folic acid supplement consumption than women aged 18--24 years (20.5%). By education level, a greater percentage of women with any college or technical school education (66.1%) reported knowledge of folic acid than those with high school or General Education Development (GED) diplomas (41.8%) and those with less than a high school education (27.1%). Those with more education also were more likely (29.2%) to consume folic acid daily. By income level, women with the highest household incomes (>$50,000) had a greater percentage of reported knowledge of folic acid (73.9%) and reported folic acid consumption (34.6%) than women with household incomes <$25,000 (52.9% and 24.4%).

Reported by: L Alvelo-Maldonado, MS; D Valencia Bernal, MS, Puerto Rico Dept of Health. AL Flores, MPH, SD Grosse, PhD, J Mulinare, MD, Div of Birth Defects and Developmental Disabilities, National Center on Birth Defects and Developmental Disabilities, CDC.

Editorial Note:

The end of the decline in NTD (i.e., spina bifida and anencephaly) prevalence in Puerto Rico in recent years is a cause for concern. The decline from 1996 to 2003 likely was aided by a campaign urging women to consume folic acid supplements and by introduction of mandatory folic acid fortification of U.S. cereal grain products in 1998. During a similar period, 1997--2003, reported folic acid supplement consumption and knowledge about folic acid increased among women in Puerto Rico, before declining from 2003 to 2006.

Since 1994, the campaign in Puerto Rico to increase the percentage of women of childbearing age who consume folic acid supplements has resulted in some success. For example, the 24.8% of Puerto Rican women who reported folic acid supplement consumption in 2006 was nearly double the 13.1% prevalence reported by Hispanic women in the mainland United States during 2001--2002 (6). However, many women in Puerto Rico associate folic acid use with pregnancy, and their vitamin consumption ends once they are no longer pregnant (7). Approximately 66% of pregnancies resulting in live births in Puerto Rico are unintended (8); however, even among Puerto Rican women who were aware of folic acid and planned their pregnancies, one study determined that only 54.8% consumed folic acid supplements before pregnancy (9).

The findings in this report are subject to at least four limitations. First, because BRFSS survey participants are limited to persons with landline telephones who are not institutionalized, findings might not be representative of the entire population of women aged 18--44 years in Puerto Rico. Second, BRFSS questions relating to folic acid consumption do not specify the recommended daily dose (400 µg) and pertain only to vitamin supplements; therefore, the findings might underestimate or overestimate the actual number of women who consumed the recommended daily dose of folic acid. Third, certain NTD-affected pregnancies might have terminated too early for registration in a hospital, and hospital staff members might not have documented all NTD cases in their log books, resulting in a lower than actual NTD prevalence. Finally, NTDs are rare, and prevalence might be influenced by even slight variations in surveillance methods.

The folic acid campaign in Puerto Rico continues. Campaign staff members attend health fairs throughout the year; and each October on Folic Acid Awareness Day, they distribute educational materials to students at 30 university campuses. In 2006, promotional activities were extended to all public primary and secondary schools. During National Birth Defects Prevention Month in January, articles are placed in newspapers, television interviews are conducted, and partner organizations help to disseminate educational materials. The campaign has developed educational materials on birth defects prevention for health professionals and teachers. However, despite these measures, only approximately one fourth of women of childbearing age in Puerto Rico consume a vitamin containing folic acid daily, suggesting that other factors might affect behavior. Additional measures directed at understanding these factors and promoting folic acid awareness and consumption among all nonpregnant Puerto Rican women of childbearing age are warranted.


  1. Mathews TJ, MacDorman MF. Infant mortality statistics from the 2004 period linked birth/infant death data set. Natl Vital Stat Rep 2007; 55(14).
  2. Puerto Rico Department of Health, Auxiliary Secretariat for Planning and Development, Division of Statistical Analysis. 2004 annual report. San Juan, Puerto Rico: Puerto Rico Department of Health.
  3. Williams LJ, Rasmussen SA, Flores A, Kirby RS, Edmonds LD. Decline in the prevalence of spina bifida and anencephaly by race/ethnicity: 1995--2002. Pediatrics 2005;116:580--6.
  4. Puerto Rico Department of Health, Auxiliary Secretariat of Family Health and Integrated Services, Mother and Child Health Care Division, Puerto Rico Birth Defects Surveillance System. 2007 annual report. San Juan, Puerto Rico: Puerto Rico Department of Health.
  5. Williams LJ, Mai CT, Edmonds LD, et al. Prevalence of spina bifida and anencephaly during the transition to mandatory folic acid fortification in the United States. Teratology 2002;66:33--9.
  6. Yang QH, Carter HK, Mulinare J, Berry RJ, Friedman JM, Erickson JD. Race-ethnicity differences in folic acid intake in women of childbearing age in the United States after folic acid fortification: findings from the National Health and Nutrition Examination Survey, 2001--2002. Am J Clin Nutr 2007;85:1409--16.
  7. Lindsey LLM, Hamner HC, Prue CE, et al. Understanding optimal nutrition among women of childbearing age in the United States and Puerto Rico: employing formative research to lay the foundation for National Birth Defects Prevention Campaigns. J Health Comm 2007;12:733--57.
  8. Puerto Rico Department of Health, Auxiliary Secretariat of Family Health and Integrated Services, Mother and Child Health Care Division, Monitoring and Evaluation Section. Puerto Rico Maternal-Infant Health Survey, 2006. San Juan, Puerto Rico: Puerto Rico Department of Health.
  9. De la Vega A, Salicrup E, Verdiales M. A nationwide program for the use of preconceptional folic acid to prevent the development of open neural tube defects. Who is really using folic acid? P R Health Sci J 2002;21:7--9.

* Participants were asked, "Do any of the vitamin pills or supplements you take contain folic acid?" Those who responded "yes" were then asked, "How often do you take this vitamin pill or supplement?"

Participants were asked, "Some health experts recommend that women take 400 micrograms of the B vitamin folic acid, for which one of the following?" "To make strong bones? To prevent birth defects? To prevent high blood pressure? Some other reason?" Only participants who responded, "To prevent birth defects," were counted as reporting knowledge of folic acid.

§ The percentage of persons who completed interviews among all eligible persons, including those who were not successfully contacted. Additional information is available at

Table 1

Table 1
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Table 2

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Figure 3
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