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Neural-Tube Defect Introduction

© Laura Ruth

Pre-natal screening is an issue for all expecting parents, and can make a pregnant mother particularly anxious. Neural-Tube Defects are a birth defect everyone worries about. Neural tube defects, such as anencephaly, spina bifida, and encephalocele, are one of the most costly types of birth defects. An NTD can cause lifetime disability. Sometimes multiple surgeries are needed to deal with severe complications, such as open lesions. It is useful to investigate whether different subgroups of people, such as Hispanics, White, Asian, and African-American, have different rates of risk for types of NTD's so that policies can be developed to prevent NTD births in high-risk groups.

Before exploring the different incidence rates of different subgroups of people, it is useful to define three open NTD's.

Anencephaly (with or without Spina Bifida) 40% defects:

open lesion in skin and skull result in nervous tissue degeneration; defective hypothalamus; excess amniotic fluid. Stillbirth or neonatal death is invariable.

Spina bifida - 55% defects:

Most commonly paralysis of legs and sphincter muscles. 15-20% closed lesions. 80% Hydrocephalus. Survival rate depends on severity and time of any surgical correction.

Encephalocele - 5% defects:

Closed skin lesions. Degree of disability varies.

Feuchtbaum and colleagues at the California Department of Health Services, Berkeley, CA surveyed over 1.6 million NTD case reports from the California Maternal Serum Alpha-Feto Protein (AFP) Screening Program, the California Birth Defects Monitoring Program, and reports from clinicians and clinics throughout the state of California. Results from the study indicate that the Hispanic population has the greatest percentage of anencephaly (46.8%) and encephalocele (41.3%) NTD's. The White subgroup represent the second largest percentage of anencephaly (35.3%) and encephalocele (34.9%) NTD's. The Asian and Black California populations represent 7.7 and 4.8% of the anencephaly NTD's and 8.7 and 7.9% encephalocele NTD's. There is a wide range of NTD incidence rates. Interestingly, the Hispanic women population has the overall highest NTD rate.

References

Feuchtbaum, L.B., Currier, R.J., Riggle, S., Roberson, M., Lorey, F.W., Cunnigham, G.C., “Neural-Tube Defect Prevalence in California (1990-1994): Eliciting Patterns by Type of Defect and Maternal Race/Ethnicity,” Genetic Testing, 3(3), 265-272, 1999.

Connor, M., Ferguson-Smith, M., Essential Medical Genetics, Blackwell Science: UK, 1997.