LABOR & ONSET OF LABOR.pptx

*
* Labor normally begins when a fetus is sufficiently
mature to cope with extrauterine life yet not too large to
cause mechanical difficulty with birth.
*"Labor" and "delivery" describe the process of childbirth.
Contractions of the uterus and changes in the cervix (the
opening of the uterus) prepare a woman's body to give birth

*
Lightening
the settling of the fetal head into the inlet of the true pelvis.
occurs approximately 2 weeks before labor in primiparas but
at unpredictable times in multiparas.
A woman notices she is not as short of breath as she was
before.
Abdominal contour is changed, and on standing may
experience frequency of urination or sciatic pain (pain across
a buttock radiating down her leg) from the lowered fetal
position.

*
Increase in Energy
Feeling extremely energetic.
Occurs as part of the body’s physiologic preparation for labor.

*
Slight Loss of Weight
As progesterone level falls. Body fluid is more easily excreted,
this increase in urine production can lead into weight loss
between 1 and 3 lb.
*
Backache
An intermittent backache stronger than usual.

*
Braxton Hicks Contractions
 Last week or days before labor a woman usually notices strong
Braxton Hicks contractions.
 A woman having her first child may have such difficulty
distinguishing between these and true contractions.
*
Ripening of the Cervix
 An internal sign seen only on pelvic examination.
 Throughout pregnancy, the cervix feels softer than normal, like the
consistency of an earlobe (Goodell’s sign)
 At term, the cervix becomes softer and can be described as “butter
soft” and it tips forward
*

*
*Signs of true labor involve uterine and cervical changes. The
more a woman knows about these labor signs, the better she
will be able to recognize them. This is helpful both to prevent
preterm birth and for the woman to feel secure knowing what
will happen during labor.

*
Uterine Contractions
True labor contractions usually start in the back and sweep
forward across the abdomen, gradually increase in frequency
and intensity.
Show
The common term used to describe the release of the cervical
plug (operculum) that formed during pregnancy. It consists of
a mucous, often blood-streaked vaginal discharge and
indicates the beginning of cervical dilatation.
Rupture of the Membranes
A sudden gush of clear fluid (amniotic fluid) from the vagina
indicates rupture of the membranes.
A woman should telephone her primary care provider
immediately when this occurs as after rupture of the
membranes, there is a danger of cord prolapse and uterine
infection.

Table26✽ IDENTIFICATIONOFLABOR
TRUELABOR FALSELABOR
RegularityofContractions Yes No
Intervals Graduallyshorten Remainlong
Intensity Graduallyincreases Unchanged
Discomfort Backandabdomen Lowerback
Cervixdilates Yes No
Discomfort relieved by
sedationorambulation
No Yes

*
 The passage refers to the route a fetus must travel from the uterus
through the cervix and vagina to the external perineum.
The pelvis is a bony ring formed by four united bones: the two
innominate (flaring hip) bones, which form the anterior and lateral
portion of the ring, and the coccyx and sacrum, which form the
posterior aspect. It serves both to support and protect the pelvic
organs.
PELVIS:
A. False Pelvis (the superior half) - supports the uterus during the late
months of pregnancy and aids in directing the fetus into the true pelvis
for birth. The false pelvis is divided from the true pelvis only by an
imaginary line, the linea terminalis. This imaginary line is drawn from
the sacral prominence at the back of the pelvis to the superior aspect
of the symphysis pubis at the front of the pelvis.

* (the inferior half) below the false
pelvis.
Inlet - is the entrance to the true pelvis, or the upper ring of bone
through which the fetus must pass to be born vaginally.
*
Outlet - is the inferior portion of the pelvis, or that portion bounded in
the back by the coccyx, on the sides by the ischial tuberosities, and in
the front by the inferior aspect of the symphysis pubis.
*
Pelvic - cavity is the space between the inlet and the outlet. This space
is not a straight but a curved passage that slows and controls the
speed of birth and therefore reduces sudden pressure changes in the
fetal head, helping prevent ruptured cerebral arteries. The snugness of
the cavity compresses the chest of the fetus as he or she passes
through, helping to expel lung fluid and mucus and thereby better
prepare the lungs for good aeration at birth.
*

True and false pelvis. Portion above linea
terminalis is false pelvis; portion below is true
pelvis. Arrow shows “stovepipe” curve that
the fetus must follow to be born.

FOUR TYPES OF PELVES:
a. Gynecoid, or “female,” pelvis has an inlet that is well rounded
forward and backward and has a wide pubic arch. This pelvic type is
ideal for childbirth.
b.Android, or “male,” pelvis, the pubic arch forms an acute angle,
making the lower dimensions of the pelvis extremely narrow. A
fetus may have difficulty exiting from this type of pelvis.
c. Anthropoid, or “ape-like,” pelvis, the transverse diameter is narrow,
and the anteroposterior diameter of the inlet is larger than normal.
This structure does not accommodate a fetal head as well as a
gynecoid pelvis.
d.Platypelloid, or “flattened,” pelvis has a smoothly curved oval inlet
but the anteroposterior diameter is shallow. A fetal head might not
be able to rotate to match the curves of the pelvic cavity.
*

FOUR TYPES OF PELVES:
Internal pelvic measurements give the actual diameters of the
inlet and outlet through which the fetus must pass. The following
measurements are made most commonly:
1.Diagonal conjugate – measurement between the anterior
surface of the sacral prominence and the posterior surface of
the symphysis pubis. The average measurement is 10.5 to 11
cm.
2.Ischial tuberosity diameter is the distance between the ischial
tuberosities, or the transverse diameter of the outlet (the
narrowest diameter at that level, or the one most apt to cause
a misfit). A diameter of 11 cm is considered adequate because
it will allow the diameter of the fetal head, or 9 cm, to pass
freely through the outlet.

Views of the pelvic inlet and outlet. (A)
Pelvic inlet. (B) Pelvic outlet.

 In most instances, if a disproportion between the fetus
and pelvis occurs (cephalo-pelvic disproportion), the
pelvis is at fault.
 When the fetus is causing the problem, it is often because
the fetal head is presented to the birth canal at less than
its narrowest diameter, not because the head is actually
too large
. Fetal head large enough for the pelvis

Effacement
 shortening and thinning of the cervical canal.
 Normally, the canal is approximately 1 to 2 cm long. With
effacement, the canal virtually disappears (Fig. 33). This
occurs because of longitudinal traction from the contracting
uterine fundus.
 Primiparas - effacement is accomplished before dilatation
begins
 Multiparas -dilatation may proceed before effacement is
complete.
CERVIX – DILATATION AND EFFACEMENT

Dilatation
 The enlargement or widening of the cervical canal from an
opening a few millimeters wide to one large enough
(approximately 10 cm) to permit passage of a fetus
 Occurs for two reason
 Uterine contractions gradually increase the diameter of the
cervical canal lumen by pulling the cervix up over the
presenting part of the fetus.
 The fluid-filled membranes press against the cervix. If the
membranes are intact, they push ahead of the fetus and serve
as an opening wedge. If they are ruptured, the presenting
part serves this same function.
CERVIX – DILATATION AND EFFACEMENT

*PERINEUM
 Episiotomy – surgical cut made to facilitate delivery; prevents
laceration
 Laceration – tearing that occurs due to trauma; may be
classified into 4 degrees
 Episiorrhapy – surgical repair of the perineal cut; suturing is
done
Types of episiotomy
VAGINAL CANAL
• Has to stretch to accommodate the passage of the fetus
• Watch out for lacerations!

*STRUCTURE OF THE FETAL SKULL
 From an obstetrical point of view, the fetal skull is the most important part
of the fetus because:
It is the largest part of the body
It is the least compressible part
It is the most frequent presenting part
 The cranium, the uppermost portion of the skull, is composed of eight
bones.
*not that important in obstetrics because they lie at the base of the
cranium, therefore, are not presenting parts.
 Sphenoid Temporal (2)
 Ethmoid
 Frontal (2 fused bones)
 Occipital
 Parietal
*
 The fetus
 The body part of a fetus that has the widest diameter is the head so this is the part
least likely to be able to pass through the pelvic ring.
 Whether a fetal skull can pass depends on its structure (bones, fontanelles and
suture lines) and its alignment with the pelvis.

 SUTURE LINES
Sagittal suture line – the membranous inter-space which joins
the 2 parietal bones
Coronal suture line – the membranous inter – space which
joins the frontal and the parietal bones
Lambdoidal suture line – the membranous inter-space that
joins the occiput and the parietal bones
* NOTE:
*Suture lines are important because they allow the
bones to move and overlap, a process called MOLDING.
*

 THE FONTANELS
Anterior fontanel – the larger fontanel; diamond – shaped, it
closes approximately between 12 – 18 months in infants
Posterior fontanel – the smaller fontanel; triangular – shaped,
it closes between 2 – 3 months in infants
The fetal skull. Lateral view

*THE DIAMETERS OF THE FETAL SKULL
the shape of the fetal skull causes it to be wider in its antero-
posterior diameter than in its transverse diameter.
Transverse diameter
 Biparietal diameter = 9.25 cm.
 Bitemporal diameter = 8 cm.
 Bimastoid diameter = 7 cm
Antero-posterior diameter
 Suboccipitobregmatic diameter =from below occiput to the
anterior fontanel (narrowest diameter = 9.5 cm.)
 Occipitofrontal diameter = from the occiput to the mid-
frontal bone (12cm.)
 Occipitomentum diameter = from the occiput to the chin
(widest at 13.5 cm)

*NOTE:
Whichever of these AP diameters is presented at the birth
canal depends on the degree of flexion (attitude) of the fetal
head.
In full flexion (very good attitude when chin is flexed on the
chest), the smallest AP diameter (suboccipitobregmatic
diameter) will be presented at the birth canal.
In moderate flexion, the occipitofrontal diameter will be
presented.
In poor flexion (extension), the widest (occipitomentum
diameter) will be the one to present = this means more
problems for the mother and the baby.

(A) Complete flexion allows the smallest diameter of the head to enter the pelvis. (B)
Moderate flexion causes a larger diameter to enter the pelvis. (C) Poor flexion forces
the largest diameter against the pelvic brim, so the head may be too large to enter the
pelvis.

 MOLDING
 A change in the shape of the fetal skull produced by the force of
uterine contractions pressing the vertex of the head against the
not-yet-dilated cervix.
 Bones of the fetal skull are not yet completely ossified and
therefore do not form a rigid structure
 Pressure causes them to overlap and molds the head into a
narrower and longer shape, a shape that facilitates passage through
the rigid pelvis.
 Overlapping of the sagittal suture line and, generally, the coronal
suture line can be easily palpated in the newborn skull.
 Molding only lasts a day or two and is not a permanent condition.
 There is little molding when the brow is the presenting part
because frontal bones are fused.
 No skull molding occurs when a fetus is breech, because the
buttocks, not the head, are presented first.

*FETAL PRESENTATION AND POSITION
 Other factors that play a part in whether a fetus is properly
aligned in the pelvis and is in the best position to be born:
Fetal Attitude
Fetal Lie
Fetal Presentation
Fetal Position

A. Fetal Attitude
 describes the degree of flexion a fetus assumes during labor or the relation of the fetal parts to
each other
Complete flexion
 the spinal column is bowed forward, the head is flexed forward so much that the chin touches the
sternum, the arms are flexed and folded on the chest, the thighs are flexed onto the abdomen, and
the calves are pressed against the posterior aspect of the thighs
 This usual “fetal position” is advantageous for birth because it helps a fetus present the smallest
anteroposterior diameter of the skull to the pelvis and also because it puts the whole body into an
ovoid shape, occupying the smallest space possible.
Moderate flexion “military attitude”
 the chin is not touching the chest but is in an alert or “military position”
 causes the next-widest anteroposterior diameter, the occipital frontal diameter, to present to the
birth canal
 This does not usually interfere with labor, because later mechanisms of labor (descent and flexion)
force the fetal head to fully flex
Partial extension
 presents the “brow” of the head to the birth canal
Complete extension
 the back is arched, and the neck is extended, presenting the occipitomental diameter of the head
to the birth canal (a face presentation)
 This unusual position presents too wide a skull diameter to the birth canal for vaginal birth. Such a
position may occur in an otherwise healthy fetus or maybe an indication there is less than the usual
amount of amniotic fluid present (oligohydramnios), which does not allow a fetus adequate
movement space.
 May reflect a neurologic abnormality in the fetus causing spasticity.
*

A. Fetal Lie
 is the relationship between the long (cephalocaudal) axis of
the fetal body and the long (cephalocaudal) axis of the
mother’s body; in other words, whether the fetus is lying in a
horizontal (transverse) or a vertical (longitudinal) position
Transverse – fewer than 4% of fetuses assume this lie
Longitudinal – approximately 96% of fetuses assume this lie
 Cephalic – the head of the fetus first comes in contact with the
mother’s cervix
 Breech – the buttocks or feet of the fetus first come in contact with
the mother’s cervix

A.Fetal Presentation
 The body part that will first contact the cervix.
 This is determined by a combination of fetal lie and the
degree of fetal flexion (attitude).
*
1.Cephalic Presentation
 A cephalic presentation is the most frequent type of
presentation, occurring as often as 96% of the time.
*NOTE:
During labor, the area of the fetal skull that contacts the cervix
often becomes edematous from the continued pressure
against it. This edema is called a caput succedaneum. In the
newborn, the point of presentation can be analyzed from the
location of the caput.
*

* TABLE 27. ✽ Four Types of Cephalic Presentation
TYPE LIE ATTITUDE DESCRIPTION
VERTEX Longitudinal Good Full
Flexion
The head is sharply flexed,
making the parietal bones or
the space between the
fontanelles (the vertex) the
presenting part. This is the
most common presentation
and allows the
suboccipitobregmatic diameter
to present to the cervix.
BROW Longitudinal Moderate
(military)
Because the head is only
moderately flexed, the brow or
sinciput becomes the
presenting part.
FACE Longitudinal Poor The fetus has extended the
head to make the face the
presenting part. From this
position, extreme edema and
distortion of the face may
occur.
The presenting diameter is so
wide that birth may be
impossible
MENTUM/
CHIN
Longitudinal Very Poor The fetus has completely
hyperextended the head to
present the chin. The widest
diameter (occipitomental) is
presenting. As a rule, a fetus
cannot enter the pelvis in this
presentation

1. Breech Presentation
 Either the buttocks or the feet of the fetus are the first body
parts to contact the cervix
Complete breech – buttocks and feet present at the birth
canal
Frank breech – The buttocks alone present at the birth canal
Footling – one foot
*NOTE:
The vertex is the most ideal presenting part because the skull
bones are capable of molding so effectively to accommodate
the cervix. It may also actually aid in the cervical dilatation
and prevent complications like prolapsed umbilical cord.
When a body part other than the vertex presents, labor is
invariably longer due to:
 ineffective descent of the fetus
 ineffective dilatation of the cervix
 irregular and weak uterine contractions.

1.Shoulder Presentation
 In a transverse lie, a fetus lies horizontally in the pelvis so that
the longest fetal axis is perpendicular to that of the mother.
 The presenting part is usually one of the shoulders (acromion
process), an iliac crest, a hand, or an elbow.
 Fewer than 1% of fetuses lie transversely.
 May be caused by relaxed abdominal walls from grand
multiparity, which allow the unsupported uterus to fall
forward.
 May be cause by pelvic contraction, in which the horizontal
space is greater than the vertical space
 Presence of Placenta previa (the placenta is located low in the
uterus, obscuring some of the vertical space) may also limit a
fetus’s ability to turn.
 preterm and smaller than usual, an attempt to turn the fetus
to a horizontal lie (external fetal version) may be made.
*

Transverseorshoulderpresentation

A.Fetal Position
 the relationship of the fetal presenting part to a specific quadrant of the
woman’s pelvis.
 For convenience, the maternal pelvis is divided into four quadrants
according to the mother’s right and left:
A. right anterior
B. left anterior
C. right posterior
D. left posterior.
 Four parts of a fetus have been chosen as landmarks to describe the
relationship of the presenting part to one of the pelvic quadrants
 In a Vertex presentation, the occiput (O) is the chosen point
 In a Face presentation, it is the chin (mentum [M])
 In a Breech presentation it is the sacrum (Sa)
 In a Shoulder presentation, it is the scapula or the acromion process. (A)
 LETTERS ARE ABBREVIATED
 The first letter denotes the mother’s right (R) or left (L)
 The middle letter denotes fetal landmark
 The last letter denotes the landmark points either anterior (A), posterior
(P) or transverse (T).
*

Table 28 ✽ Possible Fetal Positions
Vertex Presentation (occiput)
 LOA, left occipitoanterior
 LOP, left occipitoposterior
 LOT, left occipitotransverse
 ROA, right occipitoanterior
 ROP, right occipitoposterior
 ROT, right occipitotransverse
Breech Presentation (sacrum)
 LSaA, left sacroanterior
 LSaP, left sacroposterior
 LSaT, left sacrotransverse
 RSaA, right sacroanterior
 RSaP, right sacroposterior
 RSaT, right sacrotransverse
Face Presentation (mentum)
 LMA, left mentoanterior
 LMP, left mentoposterior
 LMT, left mentotransverse
 RMA, right mentoanterior
 RMP, right mentoposterior
 RMT, right mentotransverse
Shoulder Presentation (acromion process)
 LAA, left scapuloanterior
 LAP, left scapuloposterior
 RAA, right scapuloanterior
 RAP, right scapuloposterior

A.Engagement
 Refers to the settling of the presenting part of the fetus far enough
into the pelvis to be at the level of the ischial spines; a midpoint of
the pelvis
 Descent to this point means that the widest part of the fetus (the
biparietal diameter in a cephalic presentation; the intertrochanteric
diameter in breech presentation) has passed through the pelvis or
the pelvic inlet has been proven adequate for birth.
 Primigravida – non engagement of the head at the beginning of
labor indicates a possible complication, such as an abnormal
presentation or position, abnormality of the fetal head, or
cephalopelvic disproportion.
 Multipara – engagement may or may not be present at the
beginning of labor.
 A presenting part that is not engaged is termed FLOATING.
 One that is descending but has not yet reached the iliac spines is
said to be DIPPING.
 The degree of engagement is assessed by vaginal and cervical
examination.

A.Station
 The level of the presenting fetal part in the birth canal
 When the lowermost portion of the presenting fetal part is
at the level of the ischial spine  Station 0
* most often engagement of the head has
occurred; that is, the biparietal plane of the fetal
head has passed through the pelvic inlet
 The birth canal is arbitrarily divided into thirds:
*(-) = above (+) = below

Station (anteroposterior view). Station, or
degree of engagement, of the fetal head
is designated by centimeters above or
below the ischial spines. At 4 station,
head is “floating.” At 0 station, head is
“engaged.” At 4 station, head is “at
outlet.”

Head Floating Before Engagement

*
 The force supplied by the fundus of the uterus, implemented
by uterine contractions, a natural process that causes cervical
dilatation and then expulsion of the fetus from the uterus.
 After full dilatation of the cervix, the primary power is
supplemented by use of the abdominal muscles.
1. UTERINE CONTRACTIONS
 Begins at a “pacemaker” point located in the uterine
myometrium
 Consists of 3 phases:
a.Increment – when the intensity of the contraction increases
b.Acme – when the contraction is at its strongest
c. Decrement – when the intensity of the contraction decreases

*
 Duration – beginning of one to end of the same contraction
 Frequency – beginning of one to beginning of next contraction
 Intensity – strength of contraction (Peak)
 Interval – end of one contraction to beginning of next contraction
*
Maternal expulsive forces
 The most important factor to effect delivery of the infant
 Encourage pushing only during strong contractions (2nd stage) and
allow to rest thereafter
Contour Changes
 As labor contractions progress and become regular and strong, the
uterus gradually differentiates itself into 2 distinct functioning
areas
 The upper portion becomes thicker and active, preparing to exert
the force needed to expel the fetus
 The lower portion becomes thin-walled and passive to allow
passage of the fetus

The interval and duration of uterine contractions. The
frequency of contractions is the time from the beginning
of one contraction to the beginning of the next
contraction. It consists of two parts: (A) the duration of
the contraction and (B) the period of relaxation. The
broken line indicates an indeterminate period because
the relaxation time (B) is usually of longer duration than
the actual contraction (A).

TABLE 29 ✽ DIFFERENTIATING BETWEEN TRUE AND FALSE
CONTRACTIONS
False Contractions True Contractions
 Begin and remain
irregular
Begin irregularly but become regular and predictable
 Felt first
abdominally then
remain confined to
the abdomen and
groin
Felt first in lower back and sweep around to the
abdomen in a wave
 Often disappear
with ambulation or
sleep
Continue no matter what the woman’s level of
activity
 Do not increase in
duration,
frequency, or
intensity
Increase in duration, frequency, and intensity
 Do not achieve
cervical dilatation
Achieve cervical dilatation

*
 Refers to the psychological state or feelings that women bring
into labor with them
Allow the woman to ask questions to help reduce anxiety at
prenatal visits and to attend preparation for childbirth classes
helps prepare them for labor
Encouraging them to share their experience after labor serves
as “debriefing time” and helps them integrate the experience
into their total life.
Encourage support system
Encourage pain control

*
*METHODS TO MANAGE PAIN IN CHILDBIRTH
• Bradley Method – partner-coached
• Abdominal breathing – blowing candle
• Effleurage – gentle pressure/ massage in abdomen
• Ambulation – walking exercises in early labor
*
*Most approaches to reduce discomfort in labor are based on the
following three principles:
a. A woman needs to come into labor informed about what causes
labor pain and prepared with breathing exercises to use to minimize
pain during contractions.
b. A woman experiences less pain if her abdomen is relaxed and the
uterus is allowed to rise freely against the abdominal wall with
contractions.
c. Using the gating control theory of pain perception, distraction
techniques can be employed to alter how pain is received.

*
The Bradley (Partner-Coached) Method
 Originated by Robert Bradley
 Is based on the premise that childbirth is a joyful, natural
process
 The important role of the husband or partner is emphasized
during pregnancy, labor and the early newborn period
 Support system should be strengthened
The Psychosexual Method
 Pregnancy, labor, birth and early newborn period are
important points in the woman’s life cycle
 The woman is encouraged to develop conscientious relaxation
and progressive breathing techniques to allow her to “flow
with” rather than to struggle against contractions

*
The Dick Read Method
 The premise is that FEAR leads to TENSION and TENSION leads to PAIN
 Therefore, one must prevent this chain from occurring or cut the chain
between fear and tension or tension and pain to help reduce pain with
contractions
 Abdominal breathing exercises and relaxation techniques are helpful
The Lamaze Method
 Previously called PSYCHOPROPHYLACTIC method
 Through stimulus-response conditioning, women can learn to use
controlled breathing and therefore reduce pain in labor
 There are 3 main premises taught to women during the prenatal period
related to the gating control method of pain relief:
a. Pain occurs to a lesser extent if the woman is relaxed
b. Sensations such as uterine contractions can be inhibited from reaching
the brain cortex and registering as pain - - - the woman should
concentrate on breathing exercises
c. Conditioned reflexes are a positive action to use to displace pain during
labor

LABOR & ONSET OF LABOR.pptx

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