At 0 station, the baby's head is in line with which pelvic landmark, indicating engagement?

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

Answer: (A)

Descent during labor is described by station, using fixed pelvic landmarks. At zero station, the presenting part is at the level of the ischial spines, indicating engagement. The ischial spines are a palpable midpelvic landmark that marks the narrowest part the head must pass through. If the head is above the spines, the station is negative; if it is below, the station is positive. The pubic symphysis, sacral promontory, and pelvic inlet are other pelvic landmarks used for orientation, but they do not indicate engagement. So, at zero station, the head is in line with the ischial spines.