What is fetal station?
As you go through labor, your doctor will use different terms to describe how your baby is progressing through the birth canal. One of these words is your baby’s “station.”
Fetal station describes how far down your baby’s head has descended into your pelvis. Your doctor determines the fetal station by examining your cervix and finding where the lowest part of your baby is in relation to your pelvis. Your doctor will then assign a number from -5 to +5 to describe where your baby’s presenting part (usually the head) is located.
This figure represents the number of centimeters the baby has descended into the pelvis.
Determining your baby’s station
A doctor will usually perform a cervical check to determine how wide your cervix is and how far down your baby has moved. Your doctor will then assign a number from -5 to +5 to describe where your baby is in relation to the ischial spines. The ischial spines are bony protrusions located in the narrowest part of your pelvis.
During a vaginal exam, your doctor will feel for your baby’s head. If the head is high and not yet engaged in the birth canal, it may float away from their fingers. At this stage, the fetal station is -5. When your baby’s head is level with the ischial spines, the fetal station is zero. Once your baby’s head fills the vaginal opening, just before birth, the fetal station is +5.
Each change in number usually means your baby has descended another centimeter into your pelvis. However, assigning a number is an estimate.
Usually about two weeks before delivery, your baby will drop into the birth canal. This is called being “engaged.” At this point, your baby is at station 0. This drop into the birth canal is called a lightening. You will feel more room for deep breaths, but your bladder may be compressed so you’ll need to urinate often. Frequent, small amounts of urine are common. See your doctor if there is pain or burning when you urinate.
Fetal station chart
Fetal station can be important for a doctor as the American Congress of Obstetricians and Gynecologists does not recommend forceps delivery unless a baby has progressed to a certain station. Doctors measure fetal station on a scale from -5 to +5. Some doctors may use -3 to +3. Generally, the following are landmarks based on fetal station:
|Score||What this means|
|-5 to 0||The “presenting” or most palpable (able to feel) part of the baby is above the woman’s ischial spines. Sometimes a doctor can’t feel the presenting part. This station is known as the “floating.”|
|zero station||The baby’s head is known to be “engaged,” or aligned with the ischial spines.|
|0 to +5||Positive numbers are used when a baby has descended beyond the ischial spines. During birth a baby is at the +4 to +5 station.|
The number differences from -5 to -4, and so on, are equivalent to length in centimeters. So when your baby moves from zero station to +1 station, they have moved about 1 centimeter.
Why is fetal station measured?
Fetal station is important to monitor. It helps doctors evaluate how labor is progressing. Other measurements your doctor may take into account include cervical dilation, or how much your cervix has enlarged for your baby to pass through, and cervical effacement, or how thin your cervix has become to promote delivery.
Over time, if a baby isn’t progressing through the cervix, a doctor may need to consider delivery by cesarean delivery or with the help of instruments like forceps or vacuum.
Cervical examination to determine fetal station can be a fast and painless. This method is used to determine how a baby is progressing through the birth canal. This measurement is usually one of many that a doctor may use to determine labor progression.
An alternative to cervical exam for fetal station is using an ultrasound machine, which uses sound waves to determine the baby’s position. According to a study published in the journal Ultrasound in Obstetrics and Gynecology, ultrasound is usually as effective as personal examination to determine fetal position. Doctors might choose to use this imaging tool as an alternative or way to confirm what they identify as the fetal station.
One of the possible drawbacks to using fetal station is that it is an objective measurement. Each doctor bases their determination of fetal station based on where they think the ischial spines are. Two doctors could both conduct a cervical exam to try to determine fetal station and come up with two different numbers. Also, the appearance of the pelvis can vary from woman to woman. Some women may have a shorter pelvis, which could change the way a doctor would typically measure fetal station.
Another reason your doctor may want to use caution with using fetal station is that too many vaginal exams done while a woman is in labor may increase the chance of infection.
Also, it’s possible that a baby could be in a position known as the “face” presentation. This means the baby’s face, instead of the back of their head, is pointing toward the front of the mother’s pelvis. The shape of the baby’s head at this position may cause a doctor to think the baby is further down the birth canal than they really are.
Fetal station and Bishop
Fetal station is one of the components of a Bishop score. Doctors use this scoring system to determine how successful a labor induction is going and the likelihood that a woman will be able to deliver vaginally or need to have a cesarean delivery.
The five components of a Bishop score are:
- Dilation: Measured in centimeters, dilation describes how widened the cervix has become.
- Effacement: Measured in percentage, effacement is a measurement of how thin and elongated the cervix is.
- Station: Station is the measurement of the baby relative to the ischial spines.
- Consistency: Ranging from firm to soft, this describes the consistency of the cervix. The softer the cervix, the closer to delivering the baby.
- Position: This describes the position of the baby.
A Bishop’s score of less than 3 means that you are unlikely to deliver without some form of induction, like medications given to promote contractions. A Bishop’s score that’s higher than 8 means you are likely to deliver spontaneously. A doctor will assign a score ranging from 0 to 3 for each separate determination. The lowest score is 0, and the highest is 15.
The ways doctors score this are as follows:
|Score||Cervix dilation||Cervix effacement||Fetal station||Cervix position||Cervix consistency|
|0||closed||0% to 30%||-3||posterior||firm|
|1||1-2 cm||4% to 50%||-2||mid-position||moderately firm|
|2||3-4 cm||60% to 70%||-1||anterior||soft|
|3||5+ cm||80% or greater||+1||anterior||soft|
Doctors may use the Bishop’s score to justify certain medical procedures, like labor induction.
While fetal station can be imprecise, and measurements can vary from doctor to doctor, it’s an important piece of your doctor’s assessment of how your labor is progressing.