Question:medium
The flexion point in a ventouse delivery is located at which of the following positions on the fetal head?
The flexion point in a ventouse delivery is located at which of the following positions on the fetal head?
Show Hint
During a ventouse delivery, the flexion point should be approximately 3 cm anterior to the posterior fontanelle to ensure safe and effective use of the vacuum.
Updated On: Jun 22, 2026
- 3 cm posterior to the anterior fontanelle
- 3 cm anterior to the posterior fontanelle
- 6 cm anterior to the posterior fontanelle
- Midway between the anterior and posterior fontanelle
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Recall why the flexion point matters.
In a ventouse (vacuum) delivery, the cup must sit on the flexion point so that traction keeps the fetal head flexed and presents its smallest diameter to the birth canal. Place the cup wrong and the head deflexes, traction fails and scalp injury risk rises - so the question is purely about this precise landmark.
In a ventouse (vacuum) delivery, the cup must sit on the flexion point so that traction keeps the fetal head flexed and presents its smallest diameter to the birth canal. Place the cup wrong and the head deflexes, traction fails and scalp injury risk rises - so the question is purely about this precise landmark.
Step 2: Set the reference landmark.
The flexion point is defined relative to the posterior fontanelle, the small triangular junction where the sagittal suture meets the lambdoid sutures at the back of the skull. Using the posterior (not anterior) fontanelle as the anchor is the key to choosing correctly.
The flexion point is defined relative to the posterior fontanelle, the small triangular junction where the sagittal suture meets the lambdoid sutures at the back of the skull. Using the posterior (not anterior) fontanelle as the anchor is the key to choosing correctly.
Step 3: Apply the standard measurement.
The flexion point lies 3 cm anterior to the posterior fontanelle (equivalently, on the sagittal suture, about 6 cm from the anterior fontanelle). Centring the cup here optimises flexion and traction along the pelvic axis.
The flexion point lies 3 cm anterior to the posterior fontanelle (equivalently, on the sagittal suture, about 6 cm from the anterior fontanelle). Centring the cup here optimises flexion and traction along the pelvic axis.
Step 4: Discard the wrong distances.
• "3 cm posterior to the anterior fontanelle" references the wrong fontanelle and would deflex the head.
• "6 cm anterior to the posterior fontanelle" over-shoots toward the anterior fontanelle - too far forward.
• "Midway between the fontanelles" is non-specific and not the defined point.
• "3 cm posterior to the anterior fontanelle" references the wrong fontanelle and would deflex the head.
• "6 cm anterior to the posterior fontanelle" over-shoots toward the anterior fontanelle - too far forward.
• "Midway between the fontanelles" is non-specific and not the defined point.
Final answer: The flexion point is Option 2 - 3 cm anterior to the posterior fontanelle.
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