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5 PS OF LABOR

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1. POWERS

Uterine Contractions: During the first stage of

labor uterine contractions are the primary force

that moves the fetus through the maternal pelvis.

Maternal Pushing efforts: During the second stage

of labor uterine contractions continue to propel the

fetus through the pelvis. In addition, the woman feels

an urge to push and bear down as the fetus distendsher vagina and puts pressure on her rectum.

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In Labor:

Uterine contractions are rhythmic but

intermittent.

Between contractions, a period of relaxation

occurs. This allows uterine muscles to rest andprovides relief for the labouring woman. It also

restores uteroplacental circulation, which is

important to fetal oxygenation and adequate

circulation in the uterine blood vessels.

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Each contraction has three phases:

(1) Increment: building up of the contraction(longest phase)

(2) Acme: peak of the contraction

(3) Decrement: letting up of the contraction

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The terms frequency, duration, and intensity are

used to describe uterine contractions during labor.

Frequency: refers to the time between the

beginning of one contraction and the beginning ofthe next contraction.

Duration: is measured from the beginning of one

contraction to the completion of that same

contraction. Intensity: refers to the strength of the contraction

during acme.

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2. PASSAGE

The birth passage consists of the maternal pelvis and

soft tissues.

The true pelvis, which forms the bony canal through

which the fetus must pass, is divided into three sections:

the inlet, the pelvic cavity (midpelvis), and the outlet.

The Caldwell-Moloy classification is widely used to

differentiate bony pelvis types. The four classic types

are: gynecoid, android, anthropoid, and platypelloid.

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CLASSIFICATION OF PELVIS

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Implications of Pelvic Type for Labor and Birth:

Pelvic Type Pertinent Characteristics Implications for

Birth

1. Gynecoid Inlet rounded with all inlet diameters adequate

Midpelvis diameters adequate with parallel

side walls

Outlet adequate

Favorable for

vaginal birth.

2. Android Inlet heart-shaped, with short posterior sagittaldiameter

Midpelvis diamaters reduced

Outlet capacity reduced

Not favorablefor vaginal birth

Descent into

pelvis is low

3. Anthropoid Inlet oval in shape, with long anteroposterior

diameter

Midpelvis diameters adequate

Outlet adequate

Favorable for

vaginal birth

4. Platypelloid Inlet oval in shape, with long transverse

diameters

Midpelvis diameters reduced

Outlet capacity inadequate

Not favorable for

vaginal birth.

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3. PASSENGER

THE FETUS

Fetal Head

The fetal skull has three major parts: the face, base of

the skull, and the vault of the cranium (roof).

The cranial bones overlap under pressure of the powers

of labor and the demands of the unyielding pelvis. This

overlapping is called molding.

Sutures of the fetal skull: are membranous spaces

between the cranial bones.

Fontanelles: Intersections of the cranial sutures.

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Fetal Attitude

Refers to the relation of the

fetal parts to one another

The normal attitude of the

fetus is one of moderate

flexion of the head, flexion

of the arms onto the chest,and flexion of the legs onto

the abdomen.

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Fetal Lie

Relationship of the

cephalocaudal

axis of the fetus tothe cephalocaudal

axis of the mother.

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Fetal Presentation

Determined by fetal lie

Body part of the fetus that enters the pelvic passage first

This portion of the fetus is referred to as the presentingpart.

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4. Relationship between the maternalpelvis and presenting part

Engagment

- occurs when the largest

diameter of the presenting part

reaches or passes through thepelvic inlet.

- In primigravidas: 2 weeks before

term.

- In multiparas: several weeks

before the onset of labor.

-confirms the adequacy of the pelvic

inlet

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4. Relationship between the maternalpelvis and presenting part

Station

- refers to the relationship

of the presenting part to

an imaginary line drawnbetween the ischial spine

of the maternal pelvis.

- Ischial spines= Zero station

- Positive numbers indicate

that the presenting part has

passed the ischial spines.

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4. Relationship between the

maternal pelvis and presenting part

Relationship between

designated landmark

on the presenting fetal

part and the front sides,

or back of the maternal

pelvis. Most common fetal

position: occiput anterior

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5. PSYCHE

The psyche is a crucial part of childbirth. Markedanxiety and fear decrease a womans ability to copewith pain in labor.

Preparation for childbirth can enhance a womansability to work with her bodys efforts rather thanresist the natural forces.

Much of the nurses care during labor involvespromoting relaxation and reducing anxiety and fear.

Information and a positive sense of control andmastery over the birth increase the womans senseof satisfaction with her birth experience.