Download factors hypothesized to influence labor onset

GEORGIA BAPTIST COLLEGE OF NURSINGOF MERCER UNIVERSITY
NUR 330 Nursing Care of the Childbearing Family
LP4.1: Labor and Birth Processes
Student Classnotes Spring Semester 2008
1.
2.
FACTORS HYPOTHESIZED TO INFLUENCE LABOR ONSET
Uterine stretch mechanism
Hormones
 estrogen

progesterone

oxytocin

prostaglandin

Fetal cortisol
FACTORS INFLUENCING LABOR AND BIRTH PROCESSES
The combination of major factors that influence the maternal-fetal response to labor include the
(1) birth passage (true pelvis), (2) passenger (fetus), (3) powers (uterine contractions and
maternal pushing), (4) positioning (maternal) during labor and birth, (5) placenta and cord
functioning, and (6) psychological factors.
1.
Passage - True Pelvis
A.
Bony Pelvis (True Pelvis)-portion of the female pelvis that lies below the linea
terminalis. From an obstetrical perspective the bony pelvis is divided into three
planes:

inlet - bounded by the sacral promontory (fused 2nd & 3rd sacral vertebrae), linea
terminalis, and the superior edge of the symphysis pubis

midplane - bounded by the inferior edge of the symphysis pubis, the ischial
spines and the lower sacral margin

outlet - formed by two triangles.
Anterior triangle: formed by the pubic arch and the ischial tuberosities
Posterior triangle: formed by the sacral tip, the sacrosciatic ligaments and the
ischial tuberosities
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B.
2.
Soft Tissue in the True Pelvic
Note: the upper uterine segment is called the fundus and is palpable in the abdomen
from 12 weeks gestation until approximately 10-14 days after delivery.

lower uterine segment

cervix

pelvic floor muscles
Passenger (Fetus)
A. Fetal Skull
(1) Characteristics
(2) Certain sutures and fontanelles are used as clinical landmarks for
determining fetal head position during labor (see p. 246 in textbook)

Sagittal suture

Anterior fontanelle

Posterior fontanelle
B. Fetopelvic Relationships
(1) fetal presentation - portion of the fetus that enters the pelvis inlet first and
leads the fetal body through the birth canal during labor.

Cephalic (see p. 247 in textbook)

Breech (see. p. 248 in textbook)

Shoulder (see bottom of page 250 in textbook)
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(2) fetal attitude (See Figure 12-7, p. 247 in textbook)- the relationship of fetal
body parts to one another.

In cephalic presentations attitude is classified according to the degree of
flexion or extension of the fetal head.

In breech presentations attitude is classified according to the degree of
flexion or extension of the legs
(3) presenting part - the part of the fetus that lies closest to the cervical os.

During vaginal exams, this presenting part is what the examiner's hand
feels when assessing for fetal presentation and it is determined by fetal
attitude
(4) fetal lie (see p. 246, Figure 12-6 in textbook- relationship of the long axis
(spinal column) of the fetus to the long axis of the mother. Classifications:

Longitudinal

Transverse

Oblique
(5) fetal position (see pp. 248-251 in textbook):
 relationship of a designated landmark on the presenting part of the fetus
to the front, sides, or back of the maternal pelvis
 is denoted by a three letter abbreviation (Ex. ROA , LOP, RSA, RMA)

First letter denotes location a landmark on the fetal presenting part in
relation to the right or left sides of the maternal pelvis

Middle letter stands for a specific fetal landmark (0 = occiput;
S = sacrum; M = chin)

Third letter stands for location of the presenting part in relation to the
anterior (A), posterior (P), or transverse (T) portions of the mother's
pelvis
(6) station - relationship of the presenting part of the fetus to an imaginary line
drawn between the maternal ischial spines (the landmark for the midplane of
the pelvis).
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(7) engagement - term used to indicate that the largest transverse diameter of
the presenting part (most often the biparietal diameter of the fetal skull)
reaches or passes through the pelvic inlet. Engagement can be determined by
either abdominal or vaginal exam.
The following terms are used in relation to engagement:
 Floating /ballotable
 Dipping
 Fixed (Engaged)
3.
Powers - the forces of labor
A. Primary powers - involuntary uterine contractions
(1)
(2)
Uterus
 upper segment [fundus]: provides the primary power for labor & birth

Physiologic retraction ring

lower segment (passive during labor & birth)
Contraction cycle:
Increment
Acme (peak)
Decrement
Relaxation
(3) labor contractions are responsible for
 fetal descent

cervical effacement (see p. 242, Figure 12-3 in textbook)

cervical dilation
(4) contractions progressively increase in three parameters as labor progresses

frequency
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
duration

intensity
B. Secondary power
(1) Ferguson's reflex - pressure on rectum and pelvic floor that causes involuntary
pushing response
(2) Voluntary pushing vs. directed pushing
4.
Positioning of mother during labor
A. advantages of upright positions
B.
5.
disadvantages of lying positions
Placenta and umbilical cord factors
A. Implantation site
B. Perfusion quality
C. Umbilical cord
6.
Psychological responses of the mother - "Labor and birth are irrevocable events
that permanently changes the life of the mother and the entire family unit."
A.
Factors that can produce anxiety and fear in the laboring women
B.
Factors that influence the mother's psychological response to labor
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PREMONITORY SIGNS OF LABOR
1.
Braxton Hicks contractions
2.
Lightening
3.
Increased vaginal mucous secretions
4.
Cervical ripening
5.
Loss of mucus plug
6.
Sudden burst of energy (Nesting)
7.
Weight Loss
8.
Spontaneous rupture of membranes
CARDINAL MECHANISMS (MOVEMENTS) OF LABOR
The cardinal movements are the maneuvers the fetal head must complete as it passes
through the boney pelvis to the vaginal opening and is delivered. See pages 254-255 in
your OB textbook for pictures of these mechanisms.
1.
Descent
2.
Engagement
3.
Flexion
4.
Internal Rotation
5.
Extension
6.
Restitution
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7.
External Rotation
8.
Expulsion
STAGES AND PHASES OF LABOR
1.
Labor Stages
A. First Stage - from onset of "true labor" to complete dilation of the cervix. Divided
into three distinct phases
(1) Latent phase
 Cervical dilation:

Contraction Frequency _________ Duration________ Intensity________

Maternal Behavior

Average Phase Length:

Primipara:

Multipara:
(2) Active Phase
 Cervical dilation:

Contraction Frequency_________ Duration_______ Intensity ________

Maternal Behavior

Average Phase Length:
Primipara:
7
Multipara:
(3)
B.
Transition Phase
 Cervical dilation:

Contraction Frequency __________, Duration _________ Intensity_____

Maternal Behavior

Average Length: Primipara:
Multipara
Second Stage - from completion dilation through delivery of the fetus

Contraction Frequency ________ Duration _________ Intensity __________

Maternal Behavior

Average Length: Primipara:
Multipara
C. Third Stage - from delivery of the fetus through delivery of the placenta
 Contractions

Average Length:

Signs of Placental Detachment
D. Fourth Stage (synonymous with immediate postpartum period) - first 2-4 hours
after delivery of the placenta. Period in which the mother is at greatest risk for
hemorrhage.
2.
Friedman's Labor Curve (see Figure 12-13 on page 278 of textbook)
1.
MATERNAL RESPONSE TO LABOR
Cardiovascular System
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 Cardiac Output
 Blood Pressure
2.
Respiratory System
3.
Gastrointestinal System
4.
Urinary System
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Hematopoietic System
FETAL RESPONSE TO LABOR
1.
Placental Circulation
2.
Cardiovascular System
3.
Pulmonary system
"IntraProc-CLSNOTES:1-05"
1/05/SKR
Revised1/07 SKR; 1/08 SKR
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