Neural tube defects affect about 4000 pregnancies each year and are thus among the most common of severe birth defects. Prenatal diagnosis can now detect about 70% of neural tube defects but the tests produce many false positives, so the question is under what circumstances should they be recommended. This comprehensive volume - the collective knowledge of more than 55 experts in the field - provides lucid and authoritative discussions on this topic as well as on a wide variety of theoretical, experimental, and clinical issues.