Station is a term used to describe the descent of the baby into the pelvis. An imaginary line is drawn between the two bones in the pelvis (known as ischial spines). This is the "zero" line, and when the baby reaches this line it is considered to be in "zero station." When the baby is above this imaginary line it is in a minus station. When the baby is below, it is in a "plus" station. Stations are measured from -5 at the pelvic inlet to +4 at the pelvic outlet.
Station is an integral part of something known as the "Bishop’s Score." The Bishop’s Score is sometimes used to determine the chance of a successful vaginal delivery, or whether a woman may require a cesarean section. The Bishop’s Score considers station as well as other characteristics including dilation, effacement, position and consistency of the cervix.
The Bishops Score generally follows this scale:
Score Dilatation Effacement Station Position Consistency
0 closed 0 – 30% -3 posterior firm
1 1-2 cm 40 -50% -2 mid-position moderately firm
2 3-4 cm 60 -70% -1,0 anterior soft
3 5+ cm 80+% +1,+2
A point is added to the score for each of the following:
Each prior vaginal delivery
A point is subtracted from the score for:
Premature or prolonged rupture of membranes
cesarean rates: first time mothers women with past vaginal deliveries
scores of 0 – 3: 45% 7.7%
scores of 4 – 6: 10% 3.9%
scores of 7 – 10: 1.4% .9%
The more favorable the cervix and the lower the baby is in the pelvis, the less likely the need for a cesarean section. First time mothers are at particular risk for cesarean section when the cervix is not favorable.