30th June 2023

Haematology

From the beginning of pregnancy until about 34/40 there is a steady increase in plasma volume by about 40%. This results in haemodilution, causing a drop in haemoglobin concentration, haematocrit, and red cell count. There is no fall in MCV, however, the increase in iron requirements may result in concurrent iron deficiency anaemia.

An increase in WCC (mostly neutrophil driven) and a drop in platelet levels are also normal (thrombocytopenia is defined as under 100 in pregnancy).

Pregnancy results in an increase in factors V, VIII, X, and von Willebrand factor, improving the coagulation ability of women with some underlying bleeding disorders but also resulting in a significantly heightened coagulable state. This increase in clotting risk is present for up to 6/52 postpartum. There is also impaired fibrinolysis, further increasing the risk of clots.