What Does Minus 1 Mean in Labor?

what does minus 1 mean in labor
Fetal station indicates the position of the baby's head in the mother’s pelvis. A negative number (-5 to -1) means the baby’s head is not engaged

Fetal station indicates the position of the baby's head in the mother’s pelvis and indicates the progress of labor. This is represented by a number between -5 and +5. It is an imaginary line drawn between the two opposite bones of the pelvic arch (called ischial spines). 

The baby is said to be in zero station when it reaches this imaginary line. The baby is in a minus station when it is above this imaginary line. The baby is in a plus station when it is below the imaginary line.

  • Zero station: Indicates that the presenting part (usually the baby's head) is parallel to the spines.
  • Negative value (-5 to -1): Indicates that the baby’s head is not engaged in the pelvis.
  • Positive value (0 to +4): Indicates that the baby's head is moving down the pelvis, whereas a +5 indicates that the baby is crowning (being born).

It is common for a baby to be at -3, -2 or -1 during labor. Ideally, a mother should wait until the baby's head is engaged in the pelvis (at least 0) before pushing, but it is even better to wait until the baby is lower in the pelvis. This will shorten the mother's pushing time and reduce the likelihood of the birth canal swelling.

What is the Bishop score?

Fetal station is a component of the Bishop score, which assists doctors in determining whether induced labor, Cesarean delivery, or forceps delivery is required.

The Bishop score is used to determine the condition of the cervix and position of the baby in the pelvis. During a vaginal examination, the following factors are assessed to determine the total score:

  • Cervical dilation: This is the measurement of the cervix opening. It is measured in centimeters ranging from 0-10.
  • Cervical effacement: This is a measurement of the thinness and shortening of the cervix as it opens. It is measured as a percentage ranging from 0%-100%.
  • Cervical consistency: This refers to the sensation of the cervix. A hard cervix, like the tip of the nose, indicates an unfavorable cervix. A softer cervix will feel like the bottom lip or the inside of the cheek.
  • Cervical position: The cervix is usually high and facing back in a posterior position behind the baby's head before labor begins. As the body prepares for labor, the cervix lowers and moves more into a forward-facing anterior position.
  • Fetal station: This is the measurement of the baby's position in relation to the pelvic ischial spines. The ischial spines are labeled "0," whereas the area above and below the spine is labeled "+" and "-."


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What do Bishop scores mean?

A high Bishop score indicates a greater possibility of successful induction of labor. A low Bishop score indicates a lower chance of successful induction of labor. A woman with a low score of 1 is unlikely to go into labor for at least 3 weeks. A woman with a score of 10 or higher is likely to go into labor within a few days.

Although the Bishop score was originally used to assess the likelihood of vaginal delivery in women who had previously given birth (multiparous), it is now also used to assess the likelihood of vaginal delivery in women who had never given birth (nulliparous) and are being considered for induction of labor.

  • If the Bishop score is 8 or higher, there is a good chance of vaginal delivery, and the cervix is said to be favorable for induction.
  • If the Bishop score is 6 or less, the chances of vaginal delivery are slim, and the cervix is considered unfavorable for induction.

What is the safest fetal position to deliver a baby?

The best position for the baby as they approach birth is occiput anterior (OA) or vertex presentation. The baby enters the pelvis with its head down and chin tucked and facing the mother's coccyx. In this position, the head is pointing to the birth canal. It has two presentations:

  1. Face and brow presentation: The baby will remain in the OA position, but their face, instead of their head, will be pointing toward the birth canal. This occurs when the chin is not tucked against the chest and points outward, this occurs. The doctor can detect this position during a vaginal examination by feeling the baby's bony jaws and mouth. The baby will be in the OA position with their forehead pointing toward the birth canal during brow presentation.
  2. Compound presentation: The baby is facing forward with one arm lying along the head and pointing toward the birth canal. The arms may slide back during the delivery process, but if they do not, special care must be taken to deliver the baby safely.
Medline Plus. Your Baby in the Birth Canal. https://medlineplus.gov/ency/article/002060.htm

Queensland Clinical Guidelines. Induction of labour. https://www.health.qld.gov.au/__data/assets/pdf_file/0020/641423/g-iol.pdf

Cleveland Clinic. Fetal Positions for Birth. https://my.clevelandclinic.org/health/articles/9677-fetal-positions-for-birth