Correspondence

Prenatal Screening for Open Neural-Tube Defects in Maine

N Engl J Med 1999; 340:1049-1050April 1, 1999

Article

To the Editor:

In the United States, screening for open neural-tube defects is now part of routine prenatal care.1 The two most common defects (anencephaly and open spina bifida) are important causes of perinatal morbidity and mortality. Although prenatal screening with the use of maternal serum alpha-fetoprotein measurements is widespread, there is little information available on the effect such screening has on the prevalence of these defects. Such information would be helpful for health care planning. A pilot study was sponsored by the New England Regional Genetics Group, both to document the current use of prenatal screening and to establish the base-line prevalence of open neural-tube defects, before the introduction of grain products fortified with folic acid, as approved by the Food and Drug Administration.2 Folic acid supplementation reduces the occurrence of open neural-tube defects.3

Pregnancies in women from Maine with an estimated date of delivery (or actual birth) between January 1991 and December 1996, in which the fetuses were affected with open spina bifida or anencephaly, were identified from the statewide serum-screening program, diagnostic-testing centers, state vital records, and clinics that treat spina bifida. Diagnoses were confirmed by at least one additional source. Care was taken to avoid double counting of affected pregnancies, to include only open defects, and to exclude nonviable pregnancies. Records were reviewed to determine whether serum screening was performed.

Table 1Table 1Effect of Prenatal Screening and Diagnosis on Open Neural-Tube Defects in Maine. shows the number of live births in two-year periods, along with the number of affected pregnancies (and the rate of affected pregnancies per 10,000). Although the rates of prevalence of open spina bifida and anencephaly appear to have increased over time, neither trend was statistically significant. The overall rates of prevalence of open spina bifida and anencephaly were 6.4 per 10,000 (95 percent confidence interval, 4.9 to 8.8) and 4.4 per 10,000 (95 percent confidence interval, 3.1 to 6.0), respectively. During the study period, screening was carried out in 70 percent of all pregnancies in the state. A total of 96 affected pregnancies were identified. The statewide serum-screening program and diagnostic-testing centers served as the source of initial ascertainment in 67 cases, state vital records were the source in 25 cases, and spina bifida clinics were the source in 4 cases. Of the 96 affected pregnancies, 58 (60 percent) were screened.

At an alpha-fetoprotein cutoff level of 2.0 multiples of the median, 84 percent of the pregnancies in which open spina bifida was identified and 96 percent of those in which anencephaly was identified had positive results on the screening test. Eighty-one percent of the pregnancies in which open spina bifida had been identified by the screening test and 92 percent of those in which anencephaly had been identified were terminated. Several affected pregnancies were identified by ultrasonography or amniocentesis without serum screening. Overall, the prevalence of open spina bifida among births was reduced by 51 percent, and the birth prevalence of anencephaly was reduced by 79 percent. These reductions are greater than the 46 percent reduction in the birth prevalence of Down's syndrome reported earlier.4

Glenn E. Palomaki, B.S.
Josephine R. Williams
James E. Haddow, M.D.
Foundation for Blood Research, Scarborough, ME 04074

4 References

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   Food and Drug Administration. Food standards: amendment of standards of identity for enriched grain products to require addition of folic acid. Fed Regist 1996;61:8781-8797
   

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   The MRC Vitamin Study Research Group. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. Lancet 1991;338:131-137
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   Palomaki GE, Haddow JE, Beauregard LJ. Prenatal screening for Down's syndrome in Maine, 1980 to 1993. N Engl J Med 1996;334:1409-1410
   Full Text | Web of Science | Medline

Citing Articles (7)

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   Helen Harrison. (2008) The offer they can't refuse: parents and perinatal treatment decisions. Seminars in Fetal and Neonatal Medicine 13:5, 329-334
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   Stuart B. Bauer. (2008) Neurogenic bladder: etiology and assessment. Pediatric Nephrology 23:4, 541-551
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   Carol T. Norem, Edgar J. Schoen, David L. Walton, Robyn C. Krieger, Jennifer OʼKeefe, Trinh T. To, G Thomas Ray. (2005) Routine Ultrasonography Compared With Maternal Serum Alpha-fetoprotein for Neural Tube Defect Screening. Obstetrics & Gynecology 106:4, 747-752
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   Laura E. Mitchell. (2005) Epidemiology of neural tube defects. American Journal of Medical Genetics Part C: Seminars in Medical Genetics 135C:1, 88-94
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   S.B. Bauer. (2003) The management of the myelodysplastic child: a paradigm shift. BJU International 92, 23-28
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   Harold Kalter. (2003) Teratology in the 20th century. Neurotoxicology and Teratology 25:2, 131-282
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7. 7

   Oakley, Godfrey P. Jr., . (1999) Prevention of Neural-Tube Defects. New England Journal of Medicine 341:20, 1546-1546
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