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close this bookThe Clinical Use of Blood - Handbook (WHO; 2002; 222 pages)
View the documentIntroduction
open this folder and view contentsThe appropriate use of blood and blood products
open this folder and view contentsReplacement fluids
open this folder and view contentsBlood products
open this folder and view contentsClinical transfusion procedures
open this folder and view contentsAdverse effects of transfusion
open this folder and view contentsClinical decisions on transfusion
open this folder and view contentsGeneral medicine
close this folderObstetrics
View the documentKey points
View the documentHaematological changes in pregnancy
View the documentAnaemia in pregnancy
View the documentMajor obstetric haemorrhage
View the documentHaemolytic disease of the newborn (HDN)
open this folder and view contentsPaediatrics & neonatology
open this folder and view contentsSurgery & anaesthesia
open this folder and view contentsAcute surgery & trauma
open this folder and view contentsBurns
View the documentGlossary
View the documentBack cover
 

Haematological changes in pregnancy

The following haematological changes occur during pregnancy:

• 40-50% increase in plasma volume, reaching its maximum by week 32 of gestation, with similar increase in cardiac output

• Increase in red cell volume by approximately 18-25%, though more slowly than the increase in plasma volume

• Natural reduction in haemoglobin concentration: normal or elevated haemoglobin may signify pre-eclampsia in which plasma volume is reduced

• Increased iron requirement, particularly in last trimester

• Increases in platelet activation and levels of coagulation factors, particularly fibrinogen, Factor VIII and Factor IX

• Fibrinolytic system is suppressed

• Increased susceptibility to thromboembolism.

Blood loss during delivery

• About 200 ml of blood during normal vaginal delivery
• Up to 500 ml during Caesarean section.

This blood loss rarely necessitates transfusion provided that the maternal haemoglobin is above 10.0-11.0 g/dl before delivery.

Further investigation is needed if haemoglobin concentration does not return to normal by 8 weeks postpartum

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