When a healthcare provider says they can feel the baby’s head during a late-stage pregnancy check, it signals a major milestone toward birth. This phrase means the baby has descended significantly into the mother’s pelvis, moving closer to the birth canal. While the phrase is straightforward, the medical measurement behind it offers a precise understanding of how far labor has advanced. The descent of the baby’s head is closely monitored because it offers direct insight into the physical likelihood of delivery.
Defining Fetal Station and Engagement
The baby’s descent is measured using “fetal station” and “engagement.” Fetal station tracks the position of the baby’s presenting part, usually the head, relative to a fixed point in the mother’s pelvis. The fixed reference point for this measurement is the ischial spines—two small, bony protrusions located within the pelvic cavity.
When the lowest part of the baby’s head aligns exactly with the ischial spines, the fetal station is designated as zero (0). This zero station signifies that the baby’s head is “engaged,” meaning the widest part of the head has passed through the pelvic inlet. This positioning signals that the baby is ready to navigate the rest of the birth canal.
Fetal station is measured on a scale of -5 to +5, with each number representing about one centimeter. Negative numbers (-5 to -1) mean the head is still “floating” or positioned above the ischial spines. Positive numbers (+1 to +5) indicate the head has descended past the spines and is moving closer to the vaginal opening.
How the Doctor Assesses Fetal Position
Fetal station is determined through an internal, or vaginal, examination performed by the doctor or midwife. The provider uses gloved fingers to physically assess the internal pelvic structures and the baby’s position. They locate the ischial spines, which serve as the zero reference point.
By feeling the relationship between the baby’s head and these bony landmarks, the provider assigns a numerical station. If the presenting part of the head feels high, it is a negative station. If the head is pressing low, it indicates a positive station. The assigned number is an estimate based on the provider’s tactile assessment of these internal structures.
Interpreting Station: What It Means for Labor Timing
Fetal station indicates how labor is progressing and how close delivery may be. When the station is high, such as -5 to -3, the baby is not yet engaged, and labor may be in its very early stages or not yet started. For first-time mothers, the baby often reaches zero station, or engagement, weeks before labor begins, a phenomenon sometimes called “lightening.”
Reaching zero station marks a successful passage into the mid-pelvis, but it does not guarantee immediate delivery. Descent into positive stations is typically a sign of active labor, especially when accompanied by strong contractions. A station of +1 or +2 means the head has moved well beyond the ischial spines and is actively progressing through the birth canal.
Once the station reaches +3 or +4, the baby’s head is very low and close to the perineum. A station of +5 means the baby’s head is crowning and visible at the vaginal opening, signaling imminent birth. Progression through these stations is often faster for mothers who have delivered before compared to first-time mothers.
Next Steps When the Baby is Fully Engaged
When a patient reaches a positive fetal station, such as +2 or +3, the focus shifts to final preparation for delivery. The pressure from the descending head against the pelvic floor often triggers the Ferguson reflex, a strong, involuntary urge to push.
The medical team ensures the mother is fully dilated to 10 centimeters before encouraging pushing efforts. The mother may be moved to a delivery room, and the baby’s heart rate is monitored throughout the pushing stage. Optimal maternal positioning is encouraged to help the baby navigate the final curves of the birth canal. Pushing with contractions directs the baby from the lower pelvis through the vaginal opening, aiming for the +5 station and birth.