Anaemia
Plasma volume increases in pregnancy by up to 50% during first and second trimesters, whereas red cell mass (RCM) increases by only 20–30%. Haemodilution results and haemoglobin falls to a mean of 105 g/L between 16 and 40 weeks (Box 47.1). A physiological rise in mean corpuscular volume of 5–10 fl occurs. Increase in RCM, iron transfer to the fetus and blood loss during labour together require about 1000 mg iron, so that iron deficiency is frequent. Folate requirements rise because of increased catabolism. Early supplementation (e.g. 400 µg/day folic acid) reduces risk of megaloblastic anaemia and of fetal neural tube defects (see Chapter 11). The serum B12 level falls below normal in 20–30% of pregnant woman, to rise again spontaneously post-delivery. Autoimmune haemolytic anaemia in pregnancy is typically severe and refractory to therapy. Haemolytic anaemia with elevated liver enzymes and low platelets (HELLP syndrome) and epigastric pain may occur in the last trimester. Disseminated intravascular coagulation (DIC) may accompany HELLP syndrome. Induction of labour or caesarean section is often necessary.
Vitamin K-dependent factors II, VII, IX, X ↑
Factor VII ↑, von Willebrand factor ↑
Fibrinogen ↑
Protein C ↑ or no change
Antithrombin ↑ or no change
Reduced
Gestational
Iron deficiency
Folate deficiency
Bleeding, e.g. pre- or post-partem
Haemolysis (e.g. HELLP syndrome)
Pre-existing, e.g. disseminated intravascular coagulation, thalassaemia trait, sickle cell anaemia
Gestational
Immune
Pre-eclampsia
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Haemolytic anaemias V: genetic defects of haemoglobin – sickle cell disease
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Disorders of haemostasis II: inherited disorders of coagulation
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