Apart from embolism, hemorrhage remains the commonest cause of pregnancy-related death in the U.S. This prospective observational study, conducted at 19 universities, assessed the factors associated with intraoperative and postoperative packed red blood cell transfusion in women having primary or repeat cesarean delivery in the years 1999–2000.
The rate of transfusion in 23,486 primary cesarean deliveries was 3.2%. The median transfusion volume was two units. Blood was given intraoperatively in 15% of cases, postoperatively in 73%, and at both stages in 12%. Prominent factors associated with the need for transfusion were general anesthesia (odds ratio [OR], 4.2; 95% confidence interval [CI], 3.5–5.0); eclampsia or HELLP Syndrome (hemolysis, elevated liver enzymes, low platelets; O.R. 4.3; 95% CI, 3.1–6.2), placenta previa (OR, 4.8; 95% CI, 3.5–6.5); and severe preoperative anemia with a hematocrit less than 25% (OR, 17.0; 95% CI, 12.4–23.3). Other factors significantly associated with transfusion on multivariable logistic regression analysis included preeclampsia, mild preoperative maternal anemia, placental abruption, chorioamnionitis, multiple gestation, and being African American or Hispanic.
The incidence of transfusion in 33,683 repeat cesarean deliveries was 2.2%, also with a median transfusion volume of 2 units. Blood was given intraoperatively in 23% of cases, postoperatively in 59%, and during both periods in 18%. The risk of transfusion was increased by general anesthesia (OR, 7.2; 95% CI, 5.9–8.7); five or more previous cesarean deliveries (OR, 7.6; 95% CI, 4.0–14.3); placenta previa (OR, 15.9; 95% CI, 12.0–21.0); and severe preoperative anemia (OR, 19.9; 95% CI, 14.5–27.2). In addition, multivariable analysis showed that the risk of transfusion was increased by mild preoperative maternal anemia, placental abruption, chorioamnionitis, being African-American or Hispanic, and preeclampsia.
The overall need for transfusion during and/or after cesarean delivery is low, but the risk is substantially increased by severe preoperative maternal anemia and placenta previa. These findings make it important to optimize iron status antenatally so as to avoid severe anemia, and to undertake careful perioperative planning when placenta previa is present. Other considerations aside, regional anesthesia may be preferable to general anesthesia for cesarean delivery, particularly if severe anemia is present.