Blood Transfusions in Obstetrics
Anaemia Definitions and Screening
- Anaemia in pregnancy: Hb <110 g/l first trimester, <105 g/l second/third trimester, <100 g/l postpartum (BCSH-aligned).
- Screen at booking and 28 weeks; add an extra FBC at 20-24 weeks for multiple pregnancy.
- Oral iron is first-line; parenteral iron if oral is not tolerated/absorbed, compliance is doubtful, or term is near with insufficient time for oral therapy.
- Active management of the third stage minimises blood loss; women at high risk of haemorrhage should deliver where consultant-led care, blood products, and intensive care are immediately available.
Red Cell Transfusion Thresholds
- No single firm trigger exists — decide on clinical and haematological grounds, not Hb alone (acute haemorrhage can present with a normal Hb before haemodilution).
- Rule of thumb: transfusion almost always needed if Hb <60 g/l; rarely needed if Hb >100 g/l.
- Intrapartum/immediate postpartum: if Hb <70 g/l, decide individually based on history and symptoms.
- Postnatal, no ongoing bleeding: if Hb <70 g/l, decide on an informed individual basis.
- Unknown blood group in an extreme emergency: give group O RhD-negative, K-negative red cells.
Major Obstetric Haemorrhage Protocol
- Every unit needs a clear local protocol, updated annually and rehearsed in multidisciplinary skills drills.
- Immediate issue of group O, RhD-negative, K-negative red cells with no cross-match delay, switching to group-specific units when feasible.
- FFP: 12-15 ml/kg per 6 units of red cells; further dosing guided by clotting results, targeting PT/APTT ratios <1.5 × normal.
- Cryoprecipitate: two 5-unit pools given early; further dosing targets fibrinogen >1.5 g/l.
- Platelets: keep count above 50 × 10⁹/l while actively bleeding; a transfusion trigger of 75 × 10⁹/l gives a margin of safety.
- Tranexamic acid: consider during major haemorrhage in centres not in clinical trials.
- Fibrinogen concentrate: unlicensed in the UK for acquired bleeding disorders — use only within trials.
- rFVIIa: may be considered for life-threatening PPH but must never delay or replace surgery, embolisation, or transfer to a referral centre.
Cell Salvage (IOCS)
- Recommended when anticipated blood loss is enough to cause anaemia or is expected to exceed 20% of estimated blood volume.
- Consent where possible; audit and monitor use; only multidisciplinary teams with regular experience should perform it.
- RhD-negative, previously nonsensitised women with RhD-positive (or unknown) cord blood: give a minimum 1500 iu anti-D after reinfusion.
- Take a maternal Kleihauer sample 30-40 minutes post-reinfusion to check whether further anti-D is needed.
Women Who Decline Blood Products (e.g. Jehovah's Witnesses)
- Optimise Hb before delivery to avoid avoidable anaemia.
- Discuss and document consent/refusal of blood and specific components, and transfusion-sparing alternatives, antenatally.
- Use pharmacological, mechanical, and surgical measures to avert banked blood use early, not as a last resort.
- IOCS has a specific, guideline-endorsed role for patients refusing allogeneic transfusion.
- Predelivery autologous blood deposit is not recommended (poor-quality evidence, not routinely available in the UK).
High-Yield Exam Points
- Anaemia thresholds by trimester/postpartum: 110/105/100 g/l.
- Hb <60 g/l → transfuse almost always; Hb >100 g/l → rarely; no single universal trigger otherwise.
- FFP 12-15 ml/kg per 6 units RBC; cryoprecipitate two 5-unit pools; targets PT/APTT <1.5× normal and fibrinogen >1.5 g/l.
- Platelet trigger 75 × 10⁹/l vs maintenance target 50 × 10⁹/l while bleeding.
- IOCS threshold >20% of blood volume; anti-D minimum 1500 iu; Kleihauer at 30-40 minutes post-reinfusion.
- Predelivery autologous blood deposit is NOT recommended.
Source: RCOG Green-top Guideline No. 47 (May 2015 (2nd edition; not yet superseded))
Read the original on rcog.org.uk
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