His research involves Clinical Neonatal Hematology and Transfusion Medicine. Dr. Christensen was funded by the NIH for over 20 years for his studies in fetal and neonatal hematopoiesis, and he has served as a March of Dimes Study Section Member continuously for the past 22 years. He is the author of two textbooks on neonatal hematology, has written over 150 book chapters for medical books, and has published over 350 peer-reviewed articles in medical journals.