Decrease level of hematocrit in blood during pregnancy is due to?

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2018

Explanation

During pregnancy, the plasma volume expands significantly, by about 40-50%.
The red blood cell (RBC) mass also increases, but to a lesser extent, around 20-30%.
This greater increase in plasma volume compared to RBC mass leads to a dilution of the blood, a state known as hemodilution.
Hemodilution results in a lower hematocrit and hemoglobin concentration, which is a normal physiological adaptation often called 'physiological anemia of pregnancy'.

Option A: Blood loss is a pathological (abnormal) cause of decreased hematocrit, not the normal physiological reason seen in a healthy pregnancy.
Option B: Hemoconcentration is the opposite of what occurs. It involves a decrease in plasma volume relative to red blood cells, which would increase the hematocrit.
Option D: Anemia is the resulting condition or state of having low red blood cells or hemoglobin, not the underlying physiological mechanism causing the change. The question asks for the cause.

Clinical Relevance

Nursing practice connection: Knowing Physiological hematological changes during pregnancy helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses monitor hemoglobin and hematocrit levels throughout pregnancy to distinguish between normal physiological anemia and pathological anemia (e.g., iron deficiency).
Normal hematocrit in the third trimester can be as low as 33%. A drop below this level may indicate a pathological anemia requiring iron supplementation or further investigation.
Understanding hemodilution is crucial for interpreting lab results in pregnant patients and avoiding unnecessary treatments for a normal physiological change.

How to Approach the Question

First, identify the core concept of the question, which is the physiological changes in blood during pregnancy.
Recall that pregnancy involves a significant increase in total blood volume.
Analyze the components of this volume increase: both plasma and red blood cells (RBCs) increase, but not equally.
Remember that the plasma volume expansion (40-50%) is much greater than the RBC mass expansion (20-30%).
This disproportionate increase means the blood is more 'dilute.' The term for this is 'hemodilution.'
Evaluate the options: 'Blood loss' is pathological. 'Hemoconcentration' is the opposite. 'Anaemia' is the name of the condition, not the cause. Therefore, 'Hemodilution' is the direct cause of the decreased hematocrit.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 2 p. 1806-1808

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