When is a positive station number assigned during labor?

A positive station number is assigned during labor when the baby is positioned below the ischial spines in the pelvis. The ischial spines serve as a reference point in obstetrics, establishing a baseline for fetal descent through the birth canal. When the fetus descends below this landmark, the station is considered positive; for example, a station of +1 indicates that the baby is one centimeter below the ischial spines. This measurement is crucial for healthcare providers to assess how far the baby has descended and to determine the progression of labor.

The other circumstances listed do not pertain to when a positive station number is assigned. A baby above the ischial spine corresponds to a negative station. Heart rate stability is important for fetal well-being but does not relate to station. Active labor refers to a specific phase of labor defined by cervical dilation and contractions, which does not directly determine the assignment of station numbers.