Before applying a vacuum cup for assisted vaginal delivery, the operator must identify the flexion point. Where is it located?
- A On the sagittal suture, approximately 3 cm anterior to the posterior fontanelle ✓
- B Directly over the posterior fontanelle
- C Over the anterior fontanelle, centered on the bregma
- D Midway between the anterior and posterior fontanelles, whatever the head position
Correct answer: A. On the sagittal suture, approximately 3 cm anterior to the posterior fontanelle
Explanation
The flexion point lies on the sagittal suture about 3 cm in front of the posterior fontanelle. Cup placement here keeps the presenting diameter suboccipitobregmatic, the smallest possible, promoting flexion and minimizing traction force. Centering directly on the posterior fontanelle produces deflexion, and the distance from the posterior fontanelle to the flexion point is fixed rather than variable.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.