1. Division of Blood Disorders; National Center on Birth Defects and Developmental Disabilities; Centers for Disease Control and Prevention; Atlanta; GA; USA
2. Division of Reproductive Health; National Center for Chronic Disease Prevention and Health Promotion; Centers for Disease Control and Prevention; Atlanta; GA
3. McKusick-Nathans Institute of Genetic Medicine; School of Medicine; Johns Hopkins University; Baltimore; MD; USA
4. Division of Hematology; Department of Pediatrics; Johns Hopkins University School of Medicine; Baltimore; MD
5. Vanderbilt-Meharry-Matthew Walker Center of Excellence in Sickle Cell Disease; Vanderbilt University School of Medicine; Nashville; TN; USA