At which point is the presenting part of a fetus classified as at +1 station?

A fetus is classified at +1 station when its presenting part is 1 cm below the ischial spines. The fetal station is a crucial measurement used to describe the position of the fetus in relation to the ischial spines, which are bony protrusions in the pelvis. The ischial spines serve as a reference point for determining how far along the baby is in the descent through the birth canal.

In this classification system, stations are measured in centimeters with the ischial spines themselves being designated as 0 station. Stations above the ischial spines are negative (e.g., -1, -2), indicating the fetus is higher in the pelvis, while stations below the ischial spines are positive (e.g., +1, +2). Therefore, when a fetus is at +1 station, it has descended past the ischial spines and is making its way down toward the vaginal canal, specifically being 1 cm below that reference point.

This understanding is essential for labor management, as it helps healthcare professionals assess progress in labor and readiness for delivery.