Blood Transfusion and Cesarean Delivery Dwight J. Rouse, MD, MSPH, Cora MacPherson, PhD, Mark Landon, MD, Michael W. Varner, MD, Kenneth J. Leveno, MD, Atef H. Moawad, MD, Catherine Y. Spong, MD, Steve N. Caritis, MD, Paul J. Meis, MD, Ronald J. Wapner, MD, Yoram Sorokin, MD, Menachem Miodovnik, MD, Marshall Carpenter, MD, Alan M. Peaceman, MD, Mary Jo O’Sullivan, MD, Baha M. Sibai, MD, Oded Langer, MD, John M. Thorp, MD, Susan M. Ramin, MD, and Brian M. Mercer, MD, for the National Institite of Child Health and Human Development Maternal–Fetal Medicine Units Network* OBJECTIVE: To evaluate risks for intraoperative or post- operative packed red blood cell transfusion in women who underwent cesarean delivery. METHODS: This was a 19-university prospective obser- vational study. All primary cesarean deliveries from Jan- uary 1, 1999, to December 31, 2000, and all repeat cesareans from January 1, 1999, to December 31, 2002, were included. Trained, certified research nurses per- formed systematic data abstraction. Primary and repeat cesarean deliveries were analyzed separately. Univariable analyses were used to inform multivariable analyses. RESULTS: A total of 23,486 women underwent primary cesarean delivery, of whom 762 (3.2%) were transfused (median 2 units, 25th% to 75th% 2–3 units). A total of 33,683 women underwent primary cesarean delivery, and 735 (2.2%) were transfused (median 2 units, 25th% to 75th% 2– 4 units). Among primary cesareans, general anesthesia (odds ratio [OR] 4.2, 95% confidence interval [CI] 3.5–5.0), placenta previa (OR 4.8, CI 3.5– 6.5) and severe (hematocrit less than 25%) preoperative anemia (OR 17.0, CI 12.4 –23.3) increased the odds of transfusion. Among repeat cesareans, the risk was increased by gen- eral anesthesia (OR 7.2, CI 5.9 – 8.7), a history of five or more prior cesareans (OR 7.6, CI 4.0 –14.3), placenta previa (OR 15.9, CI 12.0 –21.0), and severe preoperative anemia (OR 19.9, CI 14.5–27.2). CONCLUSION: Overall, the risk of transfusion in asso- ciation with cesarean is low. However, both severe preoperative maternal anemia and placenta previa are associated with markedly increased risks. The former argues for optimizing maternal antenatal iron status to avoid severe anemia and the latter for careful perioper- ative planning when previa complicates cesarean. (Obstet Gynecol 2006;108:891–7) LEVEL OF EVIDENCE: II-2 H emorrhage is second only to embolism as a cause of pregnancy-related mortality in the United States. 1 Much of the existing data on cesarean- associated transfusion was retrospectively collected and is not contemporary. In this investigation, we have more precisely defined risk factors for the ad- ministration of packed red blood cells in association with cesarean delivery in a recently assembled, large prospective cohort. Our hope was that these data, See related article on page 885. * For members of the National Institute of Child Health and Human Develop- ment Maternal-Fetal Medicine Units Network, see the Appendix. From the Departments of Obstetrics and Gynecology, the University of Alabama at Birmingham, Birmingham, Alabama; the George Washington University Biostatistics Center, Washington, DC; Ohio State University, Columbus, Ohio; University of Utah, Salt Lake City, Utah; University of Texas Southwestern Medical Center, Dallas, Texas; University of Chicago, Chicago, Illinois; the National Institute of Child Health and Human Development, Bethesda, Maryland; University of Pittsburgh, Pittsburgh, Pennsylvania; Wake Forest University School of Medicine, Winston-Salem, North Carolina; Thomas Jefferson University, Philadelphia, Pennsylvania; Wayne State University, Detroit, Michigan; University of Cincinnati, Cincinnati, Ohio; Brown Univer- sity, Providence, Rhode Island; Northwestern University, Chicago, Illinois; University of Miami, Miami, Florida; University of Tennessee, Memphis, Tennessee; University of Texas Health Science Center at San Antonio, San Antonio, Texas; University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; University of Texas Health Science Center at Houston, Houston, Texas; and Case Western Reserve University, Cleveland, Ohio. Supported by grants From the National Institute of Child Health and Human Development (HD21410, HD21414, HD27860, HD27861, HD27869, HD27905, HD27915, HD27917, HD34116, HD34122, HD34136, HD34208, HD34210, HD40500, HD40485, HD40544, HD40545, HD40560, HD40512, and HD36801). The following core committee members participated in protocol development and coordination between clinical research centers (F. Johnson and J. McCampbell), protocol and data management and statistical analysis (Elizabeth Thom), and protocol development and oversight (John Hauth). Presented at the annual meeting of the Society for Gynecologic Investigation, Toronto, Ontario, Canada, March 22–26, 2006. Corresponding author: Dwight J. Rouse, MD, MSPH, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, 619 19th St. South, OHB 457, Birmingham, AL 35249-7333; e-mail: drouse@uab.edu. © 2006 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams & Wilkins. ISSN: 0029-7844/06 VOL. 108, NO. 4, OCTOBER 2006 OBSTETRICS & GYNECOLOGY 891