Small-for-gestational-age and large-for-gestational-age infants have polycythaemia because of?

AIIMS BBSR SNO - 2019

Child Health Nursing (Pediatrics)

Hard

Appeared in: AIIMS BBSR SNO - 2019

Explanation

Hypoxia, which refers to a state of low oxygen levels.
In the womb, a fetus experiencing chronic hypoxia (prolonged low oxygen) compensates by producing more red blood cells to maximize oxygen transport.
This process is mediated by the hormone erythropoietin, which is released in response to hypoxia and stimulates red blood cell production (erythropoiesis).
Both SGA infants (often due to placental insufficiency) and LGA infants (often from diabetic mothers, leading to high oxygen demand) can experience chronic fetal hypoxia, resulting in compensatory polycythemia.

Option A: Hypocalcaemia (low calcium) is a metabolic disturbance that can occur in high-risk newborns, but it does not stimulate red blood cell production.
Option B: Hypoglycaemia (low blood sugar) is frequently associated with polycythemia, especially in LGA infants, but it is a consequence or co-existing condition, not the cause. The increased red cell mass can actually contribute to hypoglycemia by consuming more glucose.
Option D: Hypothermia (low body temperature) is a problem related to thermoregulation, particularly in SGA infants who have less insulating body fat. It does not cause an increase in red blood cell production.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology of neonatal polycythemia in SGA and LGA infants as background academic context rather than a clinical decision trigger.
Polycythemia leads to hyperviscosity (thick blood), which can impair blood flow to vital organs, causing issues like poor feeding, lethargy, respiratory distress (tachypnea), and a ruddy (deep red) skin color.
Nurses must monitor at-risk infants (SGA, LGA, infants of diabetic mothers) for signs of polycythemia and associated complications like hypoglycemia and hyperbilirubinemia (jaundice).
A key nursing intervention is to ensure adequate hydration, as dehydration can worsen blood viscosity. In severe, symptomatic cases, a partial exchange transfusion may be performed to reduce the hematocrit.

How to Approach the Question

First, identify the key terms in the question: 'Small-for-gestational-age' (SGA), 'large-for-gestational-age' (LGA), and 'polycythaemia'.
Recall the definition of polycythemia: an abnormally high number of red blood cells.
Ask yourself what physiological process stimulates the body to make more red blood cells. The answer is the hormone erythropoietin.
Then, recall what triggers the release of erythropoietin. The primary stimulus is hypoxia (low oxygen).
Connect this back to the patient populations. Think about why SGA and LGA infants would experience hypoxia in the womb (placental insufficiency for SGA, high metabolic demand for LGA).
Evaluate the options. Eliminate those that are unrelated to red blood cell production (Hypocalcaemia, Hypothermia) and differentiate between the cause (Hypoxia) and an associated condition (Hypoglycaemia).

Concept Tested & Keywords

Concept Tested: Pathophysiology of neonatal polycythemia in SGA and LGA infants
Stem keywords: Small-for-gestational-age, large-for-gestational-age, polycythaemia
Lead-in keywords: because of

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E6 Nelson Textbook of Pediatrics(2024) — Volume 1 pp. 1056-1058, 1137-1139