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Blood Transfusion in Obstetric Patients

Author: Megan Lord, MD

Editor: Daniel J. S. Martingano, DO, MBA, PhD

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Most blood transfusions in pregnancy and the postpartum period are performed to address acute blood loss. In the first and second trimesters, this mostly results from ruptured ectopic pregnancies or incomplete abortions, and in the third trimester, from peripartum hemorrhages. Specific indications for blood product transfusion are summarized in Table 1. Packed red blood cell transfusion may be required to treat severe anemia in patients with sickle cell disease, malaria, or autoimmune conditions. Platelet transfusion is recommended to achieve a platelet count of 50,000/µL or greater in patients with thrombocytopenia who are experiencing active bleeding, or prior to surgical procedures including cesarean delivery. Fresh frozen plasma or cryoprecipitate can be used to reverse consumptive coagulopathy such as disseminated intravascular coagulation following severe hemorrhage or placental abruption.

Such hemorrhage may necessitate massive transfusion, commonly defined as transfusion of 4 or more units of packed red blood cells within 1 hour with ongoing bleeding, transfusion of 10 or more units of packed red blood cells within 24 hours, or replacement of the patient’s entire blood volume. Once these criteria are met, fixed ratios of blood products are transfused—commonly a 1:1:1 ratio of packed red blood cells, fresh frozen plasma, and platelets, mimicking whole blood. (Most blood banks store and release platelets in apheresis units or pooled units, equivalent to 6 individual units.)

When possible, packed red blood cells should be crossmatched before administration. If this is not possible, type O, Rh(D)-negative red cells should be transfused. Platelets are matched only to the Rh(D) antigen and fresh frozen plasma only to ABO type. Cryoprecipitate does not require matching. Informed consent should be obtained before transfusion when possible.

In addition to whole blood loss, during massive hemorrhage clotting factors are consumed from the blood that remains. Resuscitation with intravenous crystalloids and transfusion of packed red blood cells further dilutes these clotting factors, accelerating the emergence of coagulopathy. Fibrinogen deficits occur early, and fibrinogen replacement improves outcomes. Most massive transfusion protocols replace fibrinogen with fresh frozen plasma. This requires transfusion of large volumes and carries a higher risk of adverse events than is seen when fibrinogen is replaced via transfusion of cryoprecipitate or fibrinogen concentrates. Thus, some sources recommend adding cryoprecipitate or fibrinogen concentrates to obstetric massive transfusion protocols. Using point-of-care viscoelastic hemostatic assays, such as TEG and ROTEM, to guide transfusion decisions appears to improve outcomes and decrease costs.

The risk of adverse reactions per unit transfused is less than 0.1% for cryoprecipitate, 0.6% for red cells, 1.3% for fresh frozen plasma, and 3.8% for platelets. Overall, 2% of obstetric patients requiring massive transfusion will experience an adverse reaction. Obstetric patients receiving blood transfusions are at increased risk of posttransfusion complications, which are classified as immediate or delayed, immunologic or nonimmunologic. These are summarized in Table 2. Pretreatment with diphenhydramine and acetaminophen decreases the risk of febrile and allergic reactions. Crossmatching decreases the risk of hemolytic reactions. Fluid overload is common, frequently requiring diuresis. Patients should be monitored for hypocalcemia and hyperkalemia.

Despite these risks, under-transfusion appears more dangerous than over-transfusion.

Table 1. Typical Indications for Transfusion


Indications for transfusion

Recommended replacementa

Red cells

  • Hemoglobin <7.0 g/dL
  • Estimated blood loss ≥1500 mL with tachycardia or hypotension
  • Hemorrhage with evidence of hypoperfusion (oliguria, lactic acidosis)

One unit of packed red blood cells contains the red cells from 500 mL of whole blood from a single donor and increases serum hemoglobin by ~1.0 g/dL


  • Platelets <50,000/µL AND either active bleeding OR plan for surgery
  • Massive transfusion

One apheresis pack (single donor platelets) OR one pooled unit (the platelets from 5-6 units of whole blood, a “6-pack”) raises the platelet count by ~30,000/µL


  • Fibrinogen <200 mg/dL in an obstetric patient with bleeding
  • Active bleeding with disseminated intravascular coagulation or liver disease.

One pool of cryoprecipitate contains the fibrinogen, factor VIII, factor XIII, and vWF from 5 units of whole blood; one pool per 50 kg body weight increases fibrinogen by ~50 mg/dL

Other clotting factors

  • Active bleeding with disseminated intravascular coagulation, liver disease, warfarin use, or specific clotting factor deficiency
  • Massive transfusion

10-15 mL/kg of fresh frozen plasma increases levels of clotting factors (including fibrinogen) by ~30%; one unit is ~200 mL

a Doses assume a 70-kg adult


Table 2. Categories of Transfusion-Related Adverse Events





Acute hemolytic transfusion reaction

Febrile nonhemolytic transfusion reaction

Allergic reactions (hives, anaphylaxis)

Transfusion-related acute lung injury (TRALI)



Transfusion-associated circulatory overload (TACO)

Electrolyte abnormalities (hyperkalemia, hypocalcemia)

Viral infection


Further Reading:

Committee on Practice Bulletins-Obstetrics. Practice bulletin No. 183: postpartum hemorrhage. Obstet Gynecol. 2017;130(4):e168-e186. PMID: 28937571

Prevention and Management of Postpartum Haemorrhage: Green-top Guideline No. 52. BJOG. 2017 Apr;124(5):e106-e149. doi: 10.1111/1471-0528.14178. Epub 2016 Dec 16. PMID: 27981719.

Lord MG, Calderon JA, Ahmadzia HK, Pacheco LD. Emerging technology for early detection and management of postpartum hemorrhage to prevent morbidity. Am J Obstet Gynecol MFM. 2023 Feb;5(2S):100742. doi: 10.1016/j.ajogmf.2022.100742. Epub 2022 Sep 6. PMID: 36075527.


Final editing of initial publication performed by The Medical Pen, LLC.

Initial publication May 2023


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