Physiology of the Mother Quiz

Focused SBA-style practice, followed by the answer and explanation for every question.

Free now: 5 questions
Full bank: 41 questions
Answers: Explained

Free question

Try one with the answer

A question from this quiz. Answer it to see the explanation students get.

Which mechanism best explains the physiological anaemia observed during normal pregnancy?

A Reduced erythropoietin secretion leading to impaired red blood cell production
B Chronic blood loss from the gastrointestinal tract
C Disproportionate expansion of plasma volume relative to red blood cell mass ✓
D Increased destruction of red blood cells by the spleen
E Autoimmune haemolysis triggered by pregnancy hormones

The answer is C: Disproportionate expansion of plasma volume relative to red blood cell mass

Explanation

Why C is correct

See Cardiovascular System. Option C is correct. Pregnancy is a high-volume state in which the mother's blood volume rises from about 5 litres to about 7.5 litres. Both the plasma (the fluid part of blood) and the red cell mass (the total amount of red cells) increase, but the plasma expands proportionally more. The red cells are therefore diluted in a larger volume of fluid, so the haemoglobin concentration and the haematocrit (the proportion of blood volume taken up by red cells) both fall, even though the total number of red cells has gone up. This is the physiological anaemia of pregnancy, a normal response that is harmless in itself, although it can cause tiredness. It is accompanied by an increase in erythropoietin from the kidneys, which tries to raise red cell production. Iron tablets such as ferrous sulphate are needed only if there is true iron deficiency, because the physiological dilution alone does not need treatment. The exam trap is to attribute the fall to a disease process such as haemolysis or blood loss.

Blood volume: rises from about 5 litres to about 7.5 litres.
Plasma and red cells: both increase, but the plasma expands proportionally more.
Result: haemoglobin concentration and haematocrit fall, which is the physiological anaemia of pregnancy.
Treatment: iron is needed only if there is true iron deficiency.

Why the other options are incorrect

A. Reduced erythropoietin secretion leading to impaired red blood cell production: Erythropoietin is the kidney hormone that stimulates red cell production, and in pregnancy the kidneys release more of it, not less, as a response to the dilution. So red cell production is not impaired. This option would be right for a question about anaemia in chronic kidney disease.
B. Chronic blood loss from the gastrointestinal tract: Chronic blood loss from the gut would cause iron-deficiency anaemia, a pathological problem, and it is not part of normal pregnancy. The physiological fall in haemoglobin happens without any blood loss. This option would be right for a woman with black stools and low ferritin.
D. Increased destruction of red blood cells by the spleen: Increased destruction of red cells by the spleen would be a form of haemolytic disease (premature breakdown of red cells) and would be pathological. Normal pregnancy does not involve this. This option would be right for a patient with hereditary spherocytosis or another haemolytic anaemia.
E. Autoimmune haemolysis triggered by pregnancy hormones: Autoimmune haemolysis is destruction of red cells by the body's own antibodies, and it is a disease and not an adaptation. Pregnancy hormones do not trigger it in normal pregnancy. This option would be right for a question about autoimmune haemolytic anaemia.

Easy

With Premium, questions you miss become Revision Coach flashcards, scheduled for review.

Question preview

What you will practise

More questions from this set. Start the quiz to answer them and see each explanation.

1
Which normal change in kidney function during pregnancy contributes most to the urinary frequency that many women experience?
2
A pregnant patient reports worsening heartburn and bloating early in pregnancy despite eating smaller meals. Which physiological change best explains these gastrointestinal symptoms?

Revise before you test

Review SimpleMed's doctor-written article, then return here to check recall.

Read the topic article

Need wider coverage?

Explore every Reproductive System topic set, or build a tailored mixed session.

Browse subject quizzes