From the Guidelines
Fetal station in labor is defined as the position of the baby's presenting part in relation to the ischial spines of the mother's pelvis, measured in centimeters from -5 to +5, with 0 indicating the presenting part is at the level of the ischial spines 1. The measurement of fetal station is crucial for assessing labor progress and determining the need for interventions. To assess fetal station, the following steps should be taken:
- Perform a vaginal examination during labor
- Locate the ischial spines
- Determine the position of the presenting part relative to the spines
- Assign the appropriate station number Understanding fetal station is essential for monitoring labor progress, as it helps identify potential obstructions or labor dystocias. As labor progresses, the fetal station should descend, with +5 indicating the baby is at the perineum and ready for delivery. Providers should assess fetal station regularly during labor, typically every 1-2 hours or more frequently if needed, to ensure proper descent and identify any potential issues 1. It is also important to note that fetal station is just one aspect of labor assessment, and other factors such as cervical dilation, uterine contractions, and fetal heart rate should also be considered when evaluating labor progress. In cases where labor is not progressing as expected, further evaluation and intervention may be necessary to ensure a safe and successful delivery.
From the Research
Definition of Fetal Station in Labor
- Fetal station is traditionally based on clinical vaginal examination of the distal part of the fetal skull and related to the level of the ischial spines 2
- It can be expressed as the distance from the sacral tip to the fetal skull, measured with A-mode ultrasound, or using more convenient transperineal methods such as progression distance, angle of progression, and head-symphysis distance 2
- Fetal head descent can also be assessed transabdominally with ultrasound and measured as the suprapubic descent angle 2
Assessment of Fetal Station
- Translabial sonography can be used to diagnose fetal station in the second stage of labor, with an accuracy comparable to that of digital examination 3
- The direction of the fetal head, categorized as downward, horizontal, or upward, can be used to estimate fetal station 3
- Ultrasound measurements, such as head-perineum distance, can also be used to assess fetal station and predict labor outcome 2
Impact of Fetal Station on Labor Outcome
- Fetal head station at complete cervical dilation is significantly associated with duration of second stage of labor 4
- A higher fetal head station is associated with a longer duration of second stage of labor and an increased risk of operative delivery 4, 5
- Fetal head station can be used as a predictor of delivery mode, although its value is limited in primiparous women before labor onset 6