5 Ps of Labor

Be aware that some videos in this module contain images of an actual labor care and vaginal delivery.

"Labor-Delivery' by george ruiz, used under CC BY SA 2.0/Cropped from original

The 5 Ps of Labor are the five components that would influence the progression of labor. They are used to assess labor and how it will progress.

Hadid, N. (2019, April 16). The 5 Ps of Labor. https://www.youtube.com/watch?v=uMmNs2iNNMU&t=4s

Passenger

The Passenger refers to the fetus. The main aspects that affect whether the fetus will fit are its size and the position of the head in relation to the pelvis. First, it is clear a larger baby will have more difficulty coming through the birth canal. The position of the head deals with a couple of things: position of the head in relation to the mother’s pelvis and the angle that the head is coming into the pelvis. As seen in the following image, normally the head is the presenting part of the baby in the pelvis (known as vertex or cephalic position); if the baby is coming down other than that (breech, face presentation, or shoulder presentation) they will not fit through well, if at all. The next thing to assess is the position of the presenting part in the pelvis.

Smith, D. (2023). Fetal position in the uterus.

greek.doctor (2022, January 8). The Four Possible Positions in Occiput Presentation. https://greek.doctor/fifth-year/obstetrics-and-gynaecology-1/b25-abnormalities-of-the-fetal-position/

When the fetus is head down, we refer to the position of the occipital bone (back of the head) in the pelvis. There is a three-letter acronym used to communicate this information. The first letter refers to whether the occiput is on the right or left side of the mother’s pelvis. The second letter is the presenting part—usually O for occiput, but it can also be S for sacrum if breech, or M for mentum (chin) if it is a face presentation. The third letter communicates if the presenting part is in the anterior or posterior of the mother’s pelvis. For example, ROA would mean the baby’s occiput is on the mother’s right anterior portion of the pelvis. LSP would mean the baby is in breech presentation and the sacrum is in the mother’s left posterior portion of the pelvis.

GeekyMedics (2018, September 14). Types of Fetal Positions - OSCE Guide. https://www.youtube.com/watch?v=-CLxiLOXdH4

"A Textbook of Obstetrics" by Internet Archive Book Images, used under Public Domain/Cropped from original

RegisteredNurseRN (2020, February 17). Fetal Station Assessment and Engagement : https://www.youtube.com/watch?v=37KQoVpHc0U

Medicowsome (2014, July 22). Engagement, Syncliticism, and Asyncliticism. (https://www.youtube.com/watch?v=rXslxuZ2_tM&t=2s

Engagement of the Head

Ideally, the head of the baby is flexed with the chin resting on the chest to bring the head in at the smallest diameter. If the head is coming down straight or at a crooked position (known as asynclitism), the head will not fit through the opening of the pelvis well.

"Feminology; a Guide for Womankind, Giving in Detail Instructions as to Motherhood, Maidenhood, and the Nursery by Internet Archive Book Images, used under Public Domain/Cropped from original

There are Seven Cardinal Movements that the fetus must make to move through the pelvis: Engagement, Descent, Flexion, Internal Rotation, Extension, External Rotation, and Expulsion.

Shipley, C. (2022, March 14). Seven Cardinal MOvements of Labor: https://www.youtube.com/watch?app=desktop&v=q1jmVN3ILpY

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Passageway

The passageway refers to the mother’s pelvis. The shape of the pelvis is typically gynecoid and allows for a large heart-shaped opening for the baby to pass through. If the pelvic opening is smaller (an android pelvis), or flat (a platypelloid pelvis), or thin (an anthropoid pelvis), the presenting part of the fetus may not fit well. The laxity of soft tissues and muscles may also impede or help the progression of the fetus through the birth canal; this is one reason labor is usually faster for a woman who has had a baby already versus a primigravida.

Creogs Over Coffee (2020, November 15). Pelvimetry. https://creogsovercoffee.com/notes/2020/11/15/pelvimetry

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Powers

Primary powers refer to contraction of the uterine muscle and are measured in frequency (how often they come), duration (how long they last), and intensity (how strong they are). In active labor, contractions are usually every two to five minutes, lasting around 50–60 seconds, and increase in intensity. Intensity can be measured by palpating the uterus during a contraction and is classified as mild, moderate, or strong depending on how tightly the uterus is contracted. Also, a woman generally cannot speak through a moderate or strong contraction.
Uterine contractions will thin out the lower uterine segment and cervix; this is assessed as dilation and effacement. Dilation is the opening of the cervix—from closed to 10 centimeters. Effacement is the thinning of the cervix—from 0% to 100% (around 4 cm to paper thin).

"Essentials of Obstetrics" by Internet Archive Book Images, used under Public Domain/Cropped from original

The Vaginal Exam in Labor - Video - Global Health Media ProjectThis video shows the steps in doing this exam and the key information to gather.

Global Health Media (2015, March 11). The Vaginal Exam in Labor. https://globalhealthmedia.org/videos/the-vaginal-exam-in-labor/

NurseInTheMaking (2022, December 9). Fetal Station Overview. https://www.youtube.com/watch?v=3jlMT95Zs9U

As the contractions move the fetus through the pelvis, the station is assessed—where the presenting part is in relation to the ischial spines of the pelvis.

The point of the ischial spines is considered to be 0 station.
Above 0 station, each centimeter brings –1 through –5.
Below 0 station, the head “engages” in the pelvis, and each centimeter brings +1 through +5 where the lowest point means the head is “crowning” (or when the head is seen at the opening of the vagina and does not retract back into the vagina).

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Position

Position of the mother is important to get the head of the fetus (passenger) placed correctly into the pelvis (passageway). It’s always good to keep the woman moving in labor; even if she is laying in bed, she should be turned into different positions. Upright positions help the most to keep the pelvis moving and it allows gravity to bring the head down. Support persons can help hold or “dance” with the mother while she shifts her hips helping the positioning of the head.

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Psyche

It is important for mothers to be as relaxed as possible during labor. The amount of prenatal education preparation, stories she heard about labor, fears, previous experience with pain, and who is there for support will all influence her mental attitude going into labor. Cultural conditions should also be assessed: respecting cultural norms in labor or having translators is important.

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