The second stage of labor involves the mother pushing to move the infant through the birth canal. The decision of when to start actively pushing is governed by cervical dilation and the baby’s descent. Descent is tracked using Fetal Station, a standardized assessment that measures how far the baby’s head has traveled down into the mother’s pelvis. This measurement indicates readiness for the final stage of delivery.
Understanding Fetal Station Measurements
Fetal station is a numerical measurement indicating the position of the baby’s presenting part, usually the head, relative to the mother’s ischial spines. These spines, located in the mid-pelvis, serve as the reference point. When the lowest point of the baby’s head aligns with these spines, the station is recorded as zero (0), meaning the baby is “engaged.”
The scale uses negative numbers (-1 to -5) to indicate the head is above the spines, with -5 meaning the head is high up or “floating.” Positive numbers (+1 to +5) signify that the baby has descended past the spines and is moving into the lower birth canal. A station of +5 means the baby’s head is visible at the vaginal opening, often called crowning.
The Critical Station for Pushing
The fetal station measurement directly answers when to start pushing. Active pushing is generally discouraged until the baby has descended to a positive station, even if the mother has reached 10 centimeters of cervical dilation. Pushing when the baby is high in the pelvis (+1 or less) is inefficient and can cause maternal exhaustion.
The critical station for starting active pushing is typically +2 or +3. At this point, the baby’s head is past the narrowest portion of the pelvis, making the final descent manageable. This lower position provides better leverage, resulting in a shorter and more effective active pushing phase.
Descent to a positive station often triggers the Ferguson Reflex, the body’s natural urge to push caused by pressure on the pelvic floor. Starting to push at +2 or +3 significantly increases the likelihood of a spontaneous vaginal delivery. A lower station at the start of pushing is associated with better labor progression.
Descent and Dilation in Labor Progression
Fetal station (descent) and cervical dilation (opening) are both necessary requirements for the second stage of labor. Full dilation (10 centimeters) must be achieved before the baby can pass through, but dilation alone is insufficient if the baby has not descended adequately.
If a patient reaches 10 centimeters dilation but the baby remains at a high, negative station, active pushing is usually delayed. Providers focus on allowing contractions and gravity to move the baby down passively. This ensures the mother’s efforts during active pushing are directed toward a well-positioned baby.
The simultaneous achievement of 10-centimeter dilation and a positive fetal station, ideally +2 or +3, signals optimal conditions for delivery. Pushing when only one condition is met can increase the risk of a prolonged second stage. Healthcare providers track both measurements to guide the patient into the most productive phase of labor.
Variations in Pushing Readiness
Although +2 or +3 is the general guideline, the exact moment to begin pushing varies based on individual factors. One common variation is “laboring down,” or passive descent, often used when a mother with an epidural does not feel an immediate urge to push after full dilation.
During laboring down, the mother rests, allowing contractions to move the baby down for one to two hours. This technique conserves the mother’s energy for the final active pushing stage, often resulting in a shorter overall pushing time. The delay allows the baby to achieve a lower station, sometimes reaching +3 or +4.
The decision also depends on whether pushing is spontaneous or directed. Spontaneous pushing follows the mother’s innate urge, which occurs when the baby stimulates the pelvic nerves. Directed pushing is used when the mother has limited sensation, requiring the provider to rely heavily on the fetal station measurement.