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ANAEMIA DURING PREGNANCY
During pregnancy:
* The blood volume increases by 40%-50%. This increase started at 6 weeks to
reach it is maximum at 28 weeks –32 weeks, which is mainly due to hormonal
effect.
. Retention of sodium and water.
. Increase serum level of estrogen and progesterone.
. Increase serum level of cortisol,aldosterone, prolactin and human placental lactogen.
. The control of antidiuretic hormone is altered by pregnancy.
* The RBCs mass increases by 25%.
Which means that, there is relative increase in the plasma volume compared to the
red cell mass.
* The haematocrit and haemoglobin concentration decreases, and the
haemoglobin reaches it is lowest level at 32 weeks, when haemodilution is
maximum, and the term physiologic anaemia of pregnancy is applied to this drop in
haemoglobin.
* The serum iron levels decreases slightly but remain within the normal range with a
total iron binding capacity increases by about 15%.
* Haemoglobin level less than 10gm/dl indicate the presence of anaemia, and when it is
below 6 gm/dl, it will be associated by increase incidence of still birth and
premature infants.
* Haematocrit level of less than than 30% also indicate development of anaemia.
* The iron requirements of pregnancy are about 1000mg. This includes 500 mg used to
increase the maternal red cell mass, 300 mg transported to the fetus and placenta, and
200 mg to compensate for daily losses.
* Because dietary sources of iron are insufficient and maternal stores are unreliable at
best, iron supplementation of all pregnant women is important, as the pregnant women
will be iron deficient at term without this iron supplementation.
* The effects of maternal Iron deficiency anaemia on the fetus are very limited. Iron is
actively transported across the placenta to the fetus against a concentration gradient, with
fetal iron and ferritin levels being three to five times higher than maternal levels, and fetal
haemoglobin levels does not correlate with those of the maternal levels, and maternal Iron
deficiency anaemia does not lead to reduce in the fetal iron stores.
Anaemia
T he word anaemia connotes a decrease in the oxygen carrying capacity of the blood and it is best characterized by a reduction in haemoglobin concentration which may be relative or absolute. (The relative is not a true reduction in red cell mass and vice versa).
= Physiologic anaemia.
= Nonphysiologic anaemia.
Iron deficiency anaemia
Primary Iron deficiency anaemia is responsible for about 80% of nonphysiologic anaemias and about 1000 mg of additional iron is required during pregnancy for:
. Expansion of maternal red cell mass.
. Fetal haemoglobin.
. Iron lost due to bleeding at time of delivery.
The total body iron of the adult women about 38mg/dl.
. ˜ 70% of iron in haemoglobin.
. ˜ 30% of iron in tissues.
The iron level is achieved by control of absorption rather than control of excretion, as very minute amount is excreted normally. (About 1mg/day, and 2mg/day in menstruating women). So, the total iron content depends on absorption of iron, which occurs chiefly in the duodenum, and the rate depends on:
- The amount of iron storage.
- The rate of erythropoiesis.
Iron absorption takes place in two distinct steps:
- Mucosal uptake.
- Transfer from mucosal cell to plasma.
The mucosal uptake is influenced by the overall composition of the diet, which determine how much iron is available for absorption.
Normal mixed diet supplies 14mg of iron daily, of which only 1-2 mg is absorbed and mostly iron is presented in the ferric form which converted to ferrous form before absorption takes place.
During pregnancy, the requirements are 4 mg daily and rises maximally in the last few weeks (6.6 mg/day).
Because diet supplies only about 2mg/day, so an additional iron supplement is necessary during pregnancy.
Mild to moderate symptoms; Easy fatigability and malaise.
Severe symptoms;
. Tachycardia.
. Exertional dyspnea.
. Pallor.
. Palpitation.
Laboratory findings: depends on:
. Severity of the anaemia.
. Chronicity of the of the anaemia.
Initially iron stores are depleted, which are mainly in the bone marrow, spleen, and liver, followed by a decrease in the serum iron and increase in the total iron binding capacity and finally changes in the morphology of the red cell occur.
Serum ferritin levels less than 10ng/ml, serum iron levels less than 60ug/ml, and transferrin saturation rates less than 16% (TIBC/Serum iron), all are suggestive of Iron deficiency anaemia.
Blood film :microcytosis and hypochromia and a reticulocytic count that is low for the degree of anaemia.
If in dout: Bone marrow aspiration is recommended and the absence of stainable iron on bone marrow aspiration is diagnostic for iron deficiency.
The most important differential diagnosis is thalassemia triat since both have microcytosis and hypochromic red cells. In the triat, the serum iron ,TIBC, and stainable iron on bone marrow aspirate are within normal limits. The haemoglobin A2 level is elevated.
Up to 1 gm of oral ferrous sulfate per day ( 180mg of elemental iron ) is usually sufficient to reverse the anaemia.
When more rapid supplementation is required in severely anaemic patients or close to term, intramuscular or intravenous iron is suggested with cautions.
Effects of anaemia
- Maternal considerations:
. Post partum haemorrhage.
. Operative deliveries.
. Abruption placenta.
. Infection.
. Placental hypertrophy.
- Fetal considerations:
. Low birth weight.
. Prematurity.
. Abortion.
. Still birth.
Megaloplastic anaemia
It is the second most common cause of nutritional anaemia mostly folate deficiency, but a deficiency in Vitamin B12 also must be considered.
The patient in folate deficiency present with the typical symptoms of anaemia plus roughness of the skin and glossitis.
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E vent |
W eeks after onset of folate deficiency |
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L ow concentration of serum iron |
3 |
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H ypersegmentation of neutrophils
nuclei in peripheral blood |
7 |
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L ow folate in erythrocytes |
16 |
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M arrow ovalocytosis |
18 |
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M egaloplstic marrow |
19 |
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A naemia |
19 |
CBC:
1. Macrocytic normochromic or
Normocytic normochromic with hypersegmentation of the polymorphonuclear leukocytes.
2. The reticulocytic count is normal or low.
3. The WBCs or platelet count is normal or low.
4. The RBCs folate level is decreased and the Vitamin B12 level is normal.
Treatment
Administration of the folic acid in the dose of 1mg three times daily. But if malabsorption ,to be given parental folic acid.
A reticulocytic response should be seen in 48 hours to 72 hours and the platelet count will normalize within few days. The neutrophils will normalize after 1-2 weeks.
Vitamin B12 deficiency
Anaemia symptoms plus evidence of neurologic defects relating to damage to the posterior column of the spinal cord. The condition should not be treated with folic acid alone because anaemia may be corrected, but no effect on the neuropathy condition even may make it worse.
Normal level of folate,
Low level of Vitamin B12.
Check the serum level of intrinsic factor antibody;
If present: Pernicious anaemia
If absent: Do Schilling test.
B12 malabsorption plus intrinsic factor;
If anaemia corrected: Small intestinal disorder,
If anaemia not corrected: Pernicious anaemia.
What does this mean?
- Inadequate production of intrinsic factor (Pernicious anaemia ) or
- Malabsorption syndrome.
Treatment
1000 ugm of Vitamin B12 parentally weekly for 6 weeks followed by monthly injection for life in cases of Pernicious anaemia.
Again, a prompt reticulocytic response is anticipated after 3-5 days of therapy.
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