Chapter 12: The Process of Labor and Birth Flashcards
The 5 P’s of Labor
- Powers (physiological forces)- contractions
- Passageway (maternal pelvis)-birth canal
- Passenger (Fetus and Placenta)
- Passageway + Passenger and their relationship (engagement, attitude, position)
- Psychosocial influences (previous experiences, emotional status)
5 P’s: POWER
include the uterine contractions and the maternal pushing efforts
>Uterine muscular contractions
-primarily responsible for causing cervical effacement and dilation; also move the fetus down toward the birth canal during first stage of labor
-considered primary force of labor
>once the cervix is fully dilated, the maternal pushing efforts serve as an additional force
-during the second stage of labor, use of the maternal abdominal muscles for pushing (secondary force of labor) adds to the primary force to facilitate childbirth
Power: Uterine muscular contractions
primarily responsible for causing cervical effacement and dilation
- move the fetus down toward the birth canal during first stage of labor
- considered primary force of labor
Power: Maternal pushing efforts
once the cervix is fully dilated, the maternal pushing efforts serve as an additional force
-during the second stage of labor, use of the maternal abdominal muscles for pushing (secondary force of labor) adds to the primary force to facilitate childbirth
What are Contractions?
a rhythmic tightening of the uterus that occurs intermittently
-over time, the action shortens the individual uterine muscle fibers and aids in the process of cervical effacement and dilation, birth, and postpartal involution (reduction in uterine size after birth)
Contractions 3 distinct Components
- Increment (building of the contraction)
- Acme (peak of contraction)
- Decrement (decrease in the contraction)
What happens between Contractions?
uterus returns to a state of complete relaxation
- this rest period allows the uterine muscles to relax and provides the woman with a short recovery period that helps her to avoid exhaustion
- uterine relaxation between contractions is important for fetal oxygenation because it allows for blood flow from the uterus to the placenta to be restored
Why is Uterine Relaxation between contractions important for fetal oxygenation?
it allows for blood flow from the uterus to the placenta to be restored
Changes to the Uterine Muscular because of Contractions
- upper portion of the uterus becomes thicker and more active
- the lower uterine segment becomes thin-walled and passive
- the boundary between the upper and lower uterine segments becomes marked by a ridge on the inner uterine surface (“physiological retraction ring”)
- the uterus elongates with each contraction
Because of Contractions, the uterus elongates. What does Elongation do?
elongation causes a straightening of the fetal body so that the upper body is pressed against the fundus and the lower, presenting part is pushed toward the lower uterine segment and the cervix
-Fetal axis pressure= the pressure exerted by the fetus
>as the uterus elongates, the longitudinal muscle fibers are stretched upward over the presenting part
-this force, along with the hydrostatic pressure of the fetal membranes, causes the cervix to dilate (open)
Fetal Axis Pressure
pressure exerted by the fetus
How are Contractions Described?
frequency, duration, and intensity
How is Frequency of a Contraction Determined?
measured from the beginning of one contraction to the beginning to the next contraction
How is Duration of a Contraction Determined?
measured from the start of one contraction to the end of the same contraction
How is Intensity of a Contraction Determined?
measured by uterine palpation and is described in terms of mild, moderate, and strong
How to Palpate Contractions
noninvasive procedure
- place the fingertips of one hand on the fundus of the uterus (where most contractions can be felt)
- apply gentle pressure and keep hand in the same place (moving the hand over the uterus may stimulate additional contractions)
How to Determine The Firmness of the Uterus
Uterine fundus can determine the firmness of the uterus and whether there is an ability to indent the uterus at the acme (peak) of the contraction
-Palpating the intensity is often compared with palpating ones nose (mild intensity), chin (moderate intensity), or forehead (strong intensity)
Descriptions of Intensity for Contractions
- When uterine fundus remains soft at the acme (peak) of a contraction= “mild”
- Inability to indent the uterus at acme of a contraction= “strong”
- In between; firm fundus that is difficult to indent with the fingertips= moderate
Tocodynamometer
pressure sensitive device that is applied against the uterine fundus
-external contraction monitoring device
>when the uterus contracts, the pressure that is exerted against the “toco” is measured and recorded on graph paper
Contractions Intensity is best assed with what method?
palpation
External Electronic Monitoring
- continuous or intermittent
- provides information about the frequency and duration of contractions
- may not give accurate data regarding the intensity of contractions because of variables (e.g. maternal position, obesity, and the placement of the monitor on the uterus)
- Tocodynamometer
Internal Monitoring
-measures intensity of uterine contractions
-invasive
>if the amniotic membranes have ruptured, an internal pressure catheter is inserted through the cervix and into the uterus to measure the internal pressure generated during the contraction
Normal resting pressure (resting tone) in the uterus (between contractions)
10 to 12 mm Hg
During Acme, what is the contractions intensity range for early labor?
25 to 40 mm Hg
Intensity Contraction Range during Active Labor?
50 to 70 mm Hg
Intensity Contraction Range during Transition stage of labor?
70 to 90 mm Hg
What is the Intensity Contraction Range During Maternal Pushing in the Second Stage of Labor?
70 to 100 mm Hg
Early Labor Contraction Characteristics
- weak and irregular
- last 30 seconds
- occur every 5 to 7 minutes
- as pattern becomes known, they become regular in frequency, longer in duration, and increased in intensity
Effacement
process of shortening and thinning of the cervix
- as contractions occur, the cervix becomes shorter until the cervical canal disappears
- amount of effacement is expressed as a percentage related to the length of the cervical canal
ex: if a cervix has thinned to half the normal length of a cervix, it is 50 % effaced
Dilation
opening and enlargement of the cervix that progressively occurs throughout the first stage of labor
- expressed in centimeters (cm)
- full dilation= 10 cm
- with continued uterine contractions, the cervix eventually opens large enough to allow the fetal head to come through
How is Effacement and Dilation Evaluated?
by a vaginal examination performed by a qualified practitioner (e.g. maternity nurse who has received specialized training in this procedure)
-the vaginal exam provides info regarding diameter of the opening of the cervix (ranges from 1 cm to 10 cm), the status of the amniotic membranes (ruptured or intact), and the fetal presentation and the station, or the extent of the fetal descent through the maternal pelvis
>once the cervix is fully dilated and retracted up into the lower uterine segment, it can no longer be palpated
Maternal Pushing Efforts
after the cervix has become fully dilated, the laboring woman usually experiences involuntary “bearing down” sensation that assists with expulsion of the fetus
-at this time, the woman can use her abdominal muscles to aid in the expulsion
Why must the cervix be fully dilated before the patient is encouraged to push?
bearing down on a partially dilated cervix can cause cervical edema and damage and adversely affect the progress of labor
-the urge to bear down occurs when the fetal head reaches the pelvic floor
5 P’s: Passageway
consists of the maternal pelvis and the soft tissues
-the bony pelvis that the fetus must pass through is divided into 3 sections: inlet, mid-pelvis (pelvic cavity), and outlet
>each of these sections has a unique shape and dimension that the fetus must maneuver to be born vaginally
Four Classic Pelvis Types
- gynecoid
- android
- platypelloid
- anthropoid
5 P’s: Passenger
comprises the fetus and the fetal membranes
-fetus presents in a head-first position
Fetal Skull
-least flexible part of the fetus
-largest body structure
-because of sutures and fontanelles, there is some flexibility; allow the cranial bones the capability of movement and they overlap in response to the powers of labor
>Molding= the overlapping or overriding of the cranial bones
-consists of 3 components: the face, base of the skull, and the vault of the cranium (roof)
Fetal Lie
refers to the relationship of the long axis of the woman to the long axis of the fetus
- Longitudinal lie
- Transverse lie
- Oblique lie
Fetal Lie: Longitudinal lie
the head to tailbone axis of the fetus is the same as the woman’s
-either the fetal head or the fetal buttocks enter the pelvis first
Fetal Lie: Transverse lie
the head to tailbone axis of the fetus is at a 90-degree angle to the woman
Fetal Lie: Oblique lie
is one that is at some angle between the longitudinal an the transverse lie
Landmarks of the Fetal Skull
- Mentum: fetal chin
- Sinciput: anterior area known as the “brow”
- Bregma: large, diamond-shaped anterior fontanelle
- Vertex: area between the anterior and posterior fontanelle
- Posterior Fontanelle: the intersection between the posterior cranial sutures
- Occiput: the area of the fetal skull that is occupied by the occipital bone, beneath the posterior fontanelle
Fetal Attitude
describes the relationship of the fetus body parts to one another
-normal= attitude of flexion; “fetal position”
>can be flexion (vertex), moderate flexion (military), or extension
Fetal Attitude: Flexion (vertex)
-the fetal head is flexed, so that the chin touches the chest
-the arms are flexed and folded across the chest
-the thighs are flexed on the abdomen
-calves are flexed against the posterior aspect of the thighs
“fetal position”
Fetal Attitude: Moderate Flexion
-the fetal chin is not touching the chest but is in an alert, or “military position”
>this position causes the occipital frontal diameter to present to the birth canal
-does not interfere with labor
Fetal Attitude: Extension
presents the brow or face of the head to the birth canal
Preferred Fetal Attitude for Birth
flexion of the fetal head (which the chin touches the chest) because it allows the smallest anteroposterior diameter of the fetal skull to enter into the maternal pelvis
-any other position will present with a larger anteroposterior diameter, which contributes to a longer more difficult labor
Fetal Presentation
fetal part that enters the pelvic inlet first ad leads through the birth canal during labor
-may be cephalic, breech, or shoulder
Presenting Part
the part of the fetal body first felt by the examining finger during a vaginal examination
-is determined by the fetal lie and attitude
Fetal Presentation: Cephalic
identifies that the fetal head will be first to come in contact with the maternal cervix
-most desirable position
Advantages of the Cephalic Presentation
- fetal head is usually the largest part of the infant; once the fetal head is born, the rest of the body usually delivers without complications
- fetal head is capable of molding; there is sufficient time during labor and descent for molding of the fetal head to occur; molding helps the fetus to maneuver through the maternal birth passage
- fetal head is smooth and round, which is the optimal shape to apply pressure to the cervix and aid in dilation
4 Types of Cephalic Presentation
- Vertex
- Military
- Brow
- Face
Cephalic Presentation: Vertex
fetal head presents fully flexed
- most frequent and optimal presentation because it allows the smallest suboccipitalbregmatic diameter to present
- “vertex presentation”
Cephalic Presentation: Military
fetal head presents in a neutral position, which is neither flexed nor extended
-top of the head is the presenting part
Cephalic Presentation: Brow
fetal head is partly extended
- an unstable presentation that converts to a vertex if the head flexes or to a face presentation if the head extends
- the sinciput (fore and upper part of the cranium) is the presenting part
Cephalic Presentation: Face
fetal head is fully extended and the occiput is near the fetal spine
-face is the presenting part
Fetal Presentation: Breech
occurs when the fetal buttocks enter the maternal pelvis first
- likely occur in preterm births or in the presence of a fetal abnormality such as hydrocephaly (head enlargement caused by fluid) that prevents the head from entering the pelvis
- a C-section is usually indicated
Disadvantages Associated with A Breech Presentation
- increased risk for umbilical cord prolapse because presenting part may not be covering the cervix (e.g. footling breech)
- the presenting part (buttocks or feet) is not as smooth and hard as the fetal head and is less effective in dilating the cervix
- once the fetal body (abdomen) is delivered, the umbilical cord can become compressed; the fetus must then be delivered expeditiously to prevent hypoxia; rapid delivery may be difficult because the fetal head is usually the largest body part, and in this situation, there is no time to allow for molding
3 Different Types of Breech Presentations
- Frank
- Complete (Full)
- Footling
Breech Presentation: Frank
- most common of all breech presentations
- the fetal legs are completely extended up toward the fetal shoulders; the hips are flexed, the knees are extended, and the fetal buttocks present first in the maternal pelvis
Breech Presentation: Complete (Full)
same as the flexed position with the fetal buttocks presenting first
- legs are typically flexed
- reversal of the common cephalic presentation
Breech Presentation: Footling
one or both of the fetal legs are extended with one foot (“single footling”) or both feet (“double footling”) presenting first into the maternal pelvis
Shoulder Presentation
a transverse lie
- rare
- when a transverse lie is present, the maternal abdomen appears large from side to side, rather than up and down
- woman may also demonstrate a lower than expected (for gestational age) fundal height measurement
- shoulder usually presenting part; but fetal arm, back, abdomen, or side may present
- occurs with preterm birth, high parity, prematurely ruptured membranes, hydramnios, and placenta previa
- require C-section
Passageway + Passenger
relationship between the passageway (maternal pelvis) and the passenger (fetus and membranes)
Engagement
occurred when the widest diameter of the fetal presenting part has passed through the pelvic inlet
- determined by external palpation or vaginal examination
- occurred when the presenting part reaches stage 0
Station
the level of the presenting part in relation to the maternal ischial spines
-lies above maternal ischial spines= minus station
-lies below maternal ischial spines= positive station
>if the station does not change in the presence of strong, regular contractions, this may indicate a problem with the relationship between the maternal pelvis and the fetus (cephalopelvic disproportion)
Position
location of a fixed reference point on the fetal presenting part in relation to a specific quadrant of the maternal pelvis
-can be right anterior, left anterior, right posterior, and left posterior
-four quadrants designate whether the presenting part is directed toward the front, back, right, or left of the passageway
>Right (R) or Left (L) side of the maternal pelvis
>The Landmark of the presenting part: occiput (O), mentum (M), sacrum (S), or acromion process (A)
>Anterior (A), Posterior (P), Transverse (T): depends on whether the landmark is in the front, back, or side of maternal pelvis
ex: Right occiput anterior (ROA), Right Occiput Transverse (ROT), Right Occiput Posterior (ROP), Right Mentum Posterior (RMP)
>first and last letter refer to maternal pelvis
>middle letter refers to the presenting part of the fetus
occiput
somewhere on top of the head