Zero station is achieved when the presenting part is at which anatomical landmark?

Zero station is achieved when the presenting part is at which anatomical landmark?

• A. Pelvic inlet
• B. Ischial tuberosities
• C. Ischial spines
• D. Sacral promontory

Answer: (C)

Station describes how far the presenting part has descended relative to a fixed pelvic landmark. Zero station occurs when the presenting part is at the level of the ischial spines, which are the narrowest part of the pelvic midline. Above the spines, descent is negative (higher up in the pelvis); below the spines, descent is positive (moving toward delivery). The pelvic inlet and sacral promontory lie above the spines and correspond to negative stations, while the ischial tuberosities lie below and indicate more advanced descent.

Station describes how far the presenting part has descended relative to a fixed pelvic landmark. Zero station occurs when the presenting part is at the level of the ischial spines, which are the narrowest part of the pelvic midline. Above the spines, descent is negative (higher up in the pelvis); below the spines, descent is positive (moving toward delivery). The pelvic inlet and sacral promontory lie above the spines and correspond to negative stations, while the ischial tuberosities lie below and indicate more advanced descent.