1. FREIDA Online (database of the American Medical Association). Available at: www.freida.ama-assn.org/. 2009. Accessed March 6, 2011.
2. American Association of Nurse Anesthetists. Available at: www.aana.com/. Accessed March 6, 2011.
3. Epidemiology and the medical causes of miscarriage;Regan;Baillière’s Best Pract Res Clin Obstet Gynaecol,2000
4. Are preterm births on the decline in the United States? Recent data from the national vital statistics system. National vital statistics reports; no 39;Martin,2010
5. National rates of birth defects among hospitalized newborns;Bird;Birth Defects Res A Clin Mol Teratol,2006