Position of the fetal presenting part in relation to the ischial spines of the mother's pelvis
Ischial Spines
Bony projections on the sides of the pelvic cavity and serve as a reference point. They are located at the level of the pelvic inlet.
Zero Station (0 station)
The fetal presenting part is at the level of the ischial spines. This is the point of engagement and the starting reference for fetal descent.
Positive Stations (+1, +2, +3, etc.)
The fetal presenting part is below the ischial spines and moving closer to the vaginal opening. Positive numbers indicate further descent into the pelvis.
Negative Stations (-1, -2, -3, etc.)
The fetal presenting part is above the ischial spines and has not yet engaged. Negative numbers indicate the presenting part is higher in the pelvis.
