During labor, if the presenting part reaches the level of the ischial spines, what is the station number?

In obstetrics, station refers to the relation of the fetal presenting part to the ischial spines of the maternal pelvis. The ischial spines are anatomical landmarks that serve as a point of reference during labor. When the presenting part of the fetus is at the level of the ischial spines, it is considered to be at a station of 0.

A station of 0 indicates that the fetal head is engaged in the pelvis and is neither above nor below the ischial spines. This is a crucial point in labor, as it signifies that the fetus is positioned in a way that is favorable for descent through the birth canal. Stations above the ischial spines are denoted with negative numbers (e.g., -1 indicates the presenting part is 1 cm above the ischial spines), while stations below the ischial spines are marked with positive numbers (e.g., +1 indicates the presenting part is 1 cm below the ischial spines). Therefore, reaching station 0 is an important milestone in the progression of labor.