Page 428 - Essential Haematology

414 / Chapter 30 Pregnancy and neonatal haematology

Haematology of p regnancy sign of iron deficiency. Later, the mean corpuscular
haemoglobin (MCH) falls and fi nally anaemia
Pregnancy places extreme stresses on the haemato-
results. Early iron deficiency is likely if the serum

logical system and an understanding of the physi-
ferritin is below 15 μ g/L together with serum iron
ological changes that result is obligatory in order to
< 10 μ mol/L and should be treated with oral iron
interpret any need for therapeutic intervention.

supplements. The use of routine iron supplementa-
tion in pregnancy is debated but iron is probably
Physiological a naemia better avoided until the Hb falls below 10 g/dL or

MCV below 82 fL in the third trimester.

Physiological anaemia is the term often used to
describe the fall in haemoglobin (Hb) concentra-
tion that occurs during normal pregnancy (Fig. Folate d efi ciency
30.1 ). Blood plasma volume increases by approxi-
Folate requirements are increased approximately

mately 1250 mL, or 45%, above normal by the end
twofold in pregnancy and serum folate levels fall to
of gestation and although the red cell mass itself
approximately half the normal range with a less
increases by some 25% this still leads to a fall in Hb
dramatic fall in red cell folate. In some parts of the

concentration. Values below 10 g/dL are probably
world, megaloblastic anaemia during pregnancy is
abnormal and require investigation.
common because of a combination of poor diet and
exaggerated folate requirements. Given the protec-
Iron d efi ciency a naemia
tive effect of folate against neural tube defects

Up to 600 mg iron is required for the increase in (NTDs) as well as against anaemia, 400 μ g/day folic

red cell mass and a further 300 mg for the fetus. acid (5 mg if there has been a previous NTD preg-
Despite an increase in iron absorption, few women nancy) should be taken periconceptually and
avoid depletion of iron reserves by the end of throughout pregnancy. Food fortifi cation with
pregnancy. folate is now being practised in many countries (not
In uncomplicated pregnancy, the mean corpus- the UK) and has been associated with a fall in inci-
cular volume (MCV) typically rises by approxi- dence of NTDs. Vitamin B 12 defi ciency is rare

mately 4 fL. A fall in red cell MCV is the earliest during pregnancy although serum vitamin B 12 levels
1. Physiological anaemia
– 45% rise in blood plasma volume
– 25% rise in red cell mass
2. Thrombocytopenia
– typically a 10% fall in platelet count
3. Coagulation
– increased coagulation factors
– reduced fibrinolysis
4. Increased requirements for erythropoiesis
– 2–3 fold increase in folate requirements
– 900 mg of iron required for mother
and fetus

Figure 30.1 Haematological changes during pregnancy.