During a forceps delivery for prolonged second stage, the blades of Kielland's forceps are applied. What is the unique anatomical feature of Kielland's forceps that allows correction of asynclitism and facilitates rotation?

• A Both absent pelvic curve and a sliding lock to correct asynclitism ✓
• B Absent pelvic curve, allowing rotation in the pelvis without maternal injury
• C Sliding lock mechanism to correct asynclitism with unequal shanks
• D Presence of overlapping shanks with English lock for axis traction

Explanation

Kielland's forceps have two distinguishing features: (1) a sliding (not fixed) lock that allows the shanks to slide relative to each other, correcting asynclitism by compensating for the unequal application of the blades, and (2) a minimal (almost absent) pelvic curve, which allows the forceps to rotate the fetal head within the pelvis without the pelvic curve catching on maternal tissues. Together these features facilitate rotation from occipito-posterior or transverse positions. Standard obstetric forceps (e.g., Simpson's) have a fixed English lock and prominent pelvic curve.

Reference: Williams Obstetrics, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.