BMC Public Health 2004, 4 http://www.biomedcentral.com/1471-2458/4/16 NHIS: National Health Interview Survey http://www.biomedcentral.com/1471-2458/4/16/prepub OR: odds ratio U.S.: United States of America Competing interests None declared. Authors' contributions DFW and VN conceived the study, participated in its design, statistical analysis, and manuscript preparation. Both authors read and approved the final manuscript. Acknowledgments Dr. Wyszynski was funded by a contract from the Massachusetts Center for Birth Defects Research and Prevention of the Massachusetts Depart- ment of Public Health and by a Peer Foundation/Cleft Palate Foundation Eti- ology Research Grant. References 1. Online Mendelian Inheritance in Man (OMIM) 2003 [http:// www3.ncbi.nlm.nih.gov/Omim/mimstats.html]. 2. Fogh-Andersen P: Inheritance of harelip and cleft palate. Copenhagen: Arnold Busck 1942. 3. Christensen K, Fogh-Andersen P: Cleft lip (+/- cleft palate) in Danish twins, 1970–1990. Am J Med Genet 1993, 47:910-916. 4. Prescott NJ, Lees MM, Winter RM, Malcolm S: Identification of susceptibility loci for nonsyndromic cleft lip with or without cleft palate in a two stage genome scan of affected sib-pairs. Hum Genet 2000, 106:345-350. 5. Marazita ML, Field LL, Cooper ME, Tobias R, Maher BS, Peanchit- lertkajorn S, et al.: Genome scan for loci involved in cleft lip with or without cleft palate, in Chinese multiplex families. Am J Hum Genet 2002, 71:349-364. 6. Wyszynski DF: Locating genes for oral clefts in humans. In Cleft Lip and Palate: From Origin to Treatment Edited by: Wyszynski DF. New York : Oxford University Press; 2002:255-264. 7. Lander ES, Schork NJ: Genetic dissection of complex traits. Sci- ence 1994, 265:2037-2048. 8. Slagboom PE, Meulenbelt I: Organisation of the human genome and our tools for identifying disease genes. Biol Psychol 2002, 61:11-31. 9. Larson SA, Lakin KC, Anderson L, Kwak N, Lee JH, Anderson D: Prevalence of mental retardation and developmental disabil- ities: estimates from the 1994/1995 National Health Inter- view Survey Disability Supplements. Am J Ment Retard 2001, 106:231-52. 10. Fields JM, Casper LM: America's Families and Living Arrangements: March 2000. Current Population Reports, P20-537, U.S. Census Bureau 2001. 11. SAS Institute Inc. SAS version 8 Cary, NC; 2000. 12. StataCorp. Stata statistical software: Release 8.0. College Station: TX 2003. 13. Adams PF, Marano MA: Current estimates from the National Health Inter- view Survey, 1994. National Center for Health Statistics Vital Health Stat 10 (193): Hyattsville, MD: Department of Health and Human Services, Public Health Service Publication No. 96-1521; 1995. 14. Yoon PW, Rasmussen SA, Lynberg MC, Moore CA, Anderka M, Car- michael SL, et al.: The National Birth Defects Prevention Study. Public Health Rep 2001, 116(Suppl 1):32-40. 15. Rasmussen SA, Lammer EJ, Shaw GM, Finnell RH, McGehee RE Jr, Gallagher M, et al.: Integration of DNA sample collection into a multi-site birth defects case-control study. Teratology 2002, 66:177-184. Pre-publication history The pre-publication history for this paper can be accessed here: Publish with Bio Med Central and every scientist can read your work free of charge "BioMed Central will be the most significant development for disseminating the results of biomedical research in our lifetime." Sir Paul Nurse, Cancer Research UK Your research papers will be: available free of charge to the entire biomedical community peer reviewed and published immediately upon acceptance cited in PubMed and archived on PubMed Central yours — you keep the copyright Submit your manuscript here: http://www.biomedcentral.com/info/publishing_adv.asp BioMedcentral Page 7 of 7 (page number not for citation purposes)