Neural Tube Defect Surveillance and Folic Acid Intervention — Texas-Mexico Border, 1993-1998

Morbidity and Mortality Weekly Report, Jan 14, 2000

The findings in this report are subject to at least two limitations. First, nonresident women who migrated for birth into the United States and either returned to Mexico or to another county were not eligible for the intervention program; further, resident women who moved, were lost to followup, or had tubal ligations/hysterectomies decreased the potential intervention sample size by 40%. Second, some underestimate of cases occurred because of pregnancy outcomes that occurred outside the area.

Although a sufficient number of pregnancy outcomes have yet to occur among high-risk women to achieve statistical significance, folic acid appears to reduce the risk for NTD recurrence in Hispanic women. Unlike other U.S. surveillance systems [4,5], since its inception the TNTDP has included cases at [less than]20 weeks' gestational age. These data underscore the importance of a timely and active NTD surveillance system that includes fetuses at [less than]20 weeks' gestational age for population-based and individual NTD prevention. They also highlight the need for physicians to educate their high-and low-risk patients about the benefits of folic acid [6,7].

References

(1.) Hendricks KA, Simpson JS, Larsen RD. Neural tube defects along the Texas-Mexico border, 1993-1995. Am J Epidemiol 1999;149:1119-27.

(2.) Moore CA, Li S, Li Z, et al. Elevated rates of severe neural tube defects in a high prevalence area in Northern China. Am J Med Genet 1997;73:113-8.

(3.) CDC. Knowledge and use of folic acid by women of childbearing age--United States, 1995. MMWR 1995;44:716-8.

(4.) Roberts HE, Moore CA, Cragen JD, et al. Impact of prenatal diagnosis on the birth prevalence of neural tube defects, Atlanta, 1990-1991. Pediatrics 1995;96:880-3.

(5.) Velie EM, Shaw GM. Impact of prenatal diagnosis and elective termination on prevalence and risk estimates of neural tube defects in California, 1989-1991. Am J Epidemiol 1996;144:473-9.

(6.) Smithells RW, Seller MJ, Nevin NC, et al. Further experience of vitamin supplementation for prevention of neural tube defect recurrences. Lancet 1983;1:1027-31.

(7.) American Academy of Pediatrics, Committee on Genetics. Folic acid for the prevention of neural tube defects. Pediatrics 1999;104:325-7.

            Neural tube defect (NTD) type [*] and rate, [ ] by
           county of residence -- Texas-Mexico border, 1993-1998
         Anencephaly [ss]      Spina bifida                All NTDs
County    No. cases       Rate  No. cases   Rate Total [n]   Rate
Cameron       31          6.7       38      8.2    73        15.8
El Pasco      39          4.3       36      4.0    82         9.0
Hidalgo       48          6.2       60      7.7   118        15.1
Webb          28          9.3       19      6.3    51        16.9
Other 10      17          7.1       17      7.1    36        14.9
Total        163          6.1      170      6.3   360        13.4
County   (95% CI [**])
Cameron   (12.4-19.8)
El Pasco  ( 7.2-11.2)
Hidalgo   (12.5-18.1)
Webb      (12.6-22.2)
Other 10  (10.5-20.7)
Total     (12.0-14.8)