EFM Fetal Oxygenation and Acid-Base Balance 1 — Questions and Answers
Question 1: What is the normal pH range for umbilical artery blood at delivery?
- 7.10 – 7.20
- 7.25 – 7.35 (Correct answer)
- 7.05 – 7.15
- 7.40 – 7.50
Correct answer: 7.25 – 7.35
A normal umbilical artery pH at delivery is 7.25–7.35, reflecting adequate fetal acid-base status.
Question 2: Which type of acidosis is characterized by an elevated PCO2 and normal base deficit in fetal cord blood?
- Metabolic acidosis
- Mixed acidosis
- Respiratory acidosis (Correct answer)
- Lactic acidosis
Correct answer: Respiratory acidosis
Respiratory acidosis results from acute CO2 accumulation (elevated PCO2) without significant base deficit, often due to transient cord compression.
Question 3: The primary mechanism by which oxygen crosses the placenta from mother to fetus is:
- Active transport
- Facilitated diffusion
- Simple diffusion (Correct answer)
- Pinocytosis
Correct answer: Simple diffusion
Oxygen crosses the placental membrane via simple diffusion down a partial pressure gradient from maternal to fetal blood.
Question 4: A base deficit greater than which value is considered significant for metabolic acidosis in the newborn?
- 4 mmol/L
- 8 mmol/L
- 12 mmol/L (Correct answer)
- 16 mmol/L
Correct answer: 12 mmol/L
A base deficit greater than 12 mmol/L in umbilical artery blood is the threshold associated with significant metabolic acidosis and potential neonatal morbidity.
Question 5: Which fetal blood vessel carries oxygenated blood FROM the placenta TO the fetus?
- Umbilical artery
- Umbilical vein (Correct answer)
- Ductus arteriosus
- Ductus venosus
Correct answer: Umbilical vein
The umbilical vein carries oxygenated, nutrient-rich blood from the placenta to the fetus.
Question 6: Fetal hypoxia is defined as:
- Insufficient glucose delivery to fetal tissues
- Inadequate oxygen delivery to fetal tissues (Correct answer)
- Excessive CO2 accumulation in fetal blood
- Decreased fetal cardiac output
Correct answer: Inadequate oxygen delivery to fetal tissues
Fetal hypoxia is defined as inadequate oxygen delivery to fetal tissues, which can lead to anaerobic metabolism and acidosis if prolonged.
Question 7: In fetal cord blood gas analysis, which value best reflects fetal metabolic status?
- PCO2
- PO2
- Base deficit (Correct answer)
- pH alone
Correct answer: Base deficit
Base deficit best reflects the degree of metabolic acidosis because it measures the amount of buffer (bicarbonate) consumed, independent of respiratory changes.
EFM Fetal Oxygenation and Acid-Base Balance 1
What is the normal pH range for umbilical artery blood at delivery?