DYSTOCIA DUE TO EXPULSIVE FORCES, FETOPELVIC

DISPROPORTION AND MATERNAL – FETAL ANOMALIES

DYSTOCIA - ABNORMAL LABOR

� difficult labor characterized by abnormally slow progress of labor

Four distinct abnormalities

� Abnormalities of the expulsive forces

� Abnormalities of presentation, position, or development of the fetus.

� Abnormalities of the maternal bony pelvis

� Abnormalities of soft tissues of the reproductive tract

Categories according to the American College of Obstetricians and Gynecologists

� Abnormalities of the powers—uterine contractility and maternal expulsive

effort.

� Abnormalities involving the passenger—the fetus.

� Abnormalities of the passage—the pelvis.

Mechanisms of Dystocia

At the end of pregnancy:

� Obstacles for the fetal head to traverse the birth canal:

� uterine contractions

� cervical resistance

� forward pressure exerted by the leading fetal head

� Factors influencing the progress of the 1st

stage of labor

� thicker lower uterine segment

� undilated cervix

� uterine muscle is less developed and presumably less powerful.

� After complete cervical dilatation (2nd

Stage):

the mechanical relationship between the following is clearer:

� fetal head size and position } fetopelvic

� the pelvic capacity } proportion

� uterine musculature is much thicker and thus more powerful

� abnormalities in fetopelvic disproportions become more apparent

Uterine muscle malfunction can result from

� uterine overdistention or

� obstructed labor

� Thus ineffective labor is a possible warning sign of fetopelvic disproportion

� Uterine dysfunction } labor abnormalities

� Pelvic disproportion } so closely interlinked

Diagrams of the birth canal (A) at the end of pregnancy and (B) during the second

stage of labor, showing formation of the birth canal. (C.R. = contraction ring; o.i. =

internal cervical os; o.e. = external cervical os.) (From Williams, 1903.)

ABNORMALITIES OF THE EXPULSIVE FORCES

� 1ST

STAGE OF LABOR: Contractions of the uterus �cervical dilatation,

propulsion and expulsion of the fetus

� 2ND

STAGE OF LABOR: Contractions of the uterus or involuntary muscular

action of abdominal wall --“PUSHING”

Uterine dysfunction

� characterized by lack of progress of labor

2 Types of Uterine Dysfunction

� Hypotonic Uterine Dysfunction

� More common

� No basal hypertonus

� Uterine contractions have a normal gradient pattern

(synchronous)

� Slight rise in pressure during a contraction is insufficient to dilate

the cervix

� Treatment: Oxytocin

� Hypertonic/Incoordinate Uterine Dysfunction

� Basal tone is elevated

� Pressure gradient is distorted (asynchronism)

� Treatment: sedation

Reported Causes of Uterine Dysfunction

� Various labor factors have been implicated as causes of uterine

dysfunction

� Epidural Analgesia

� epidural analgesia can slow labor

� epidural analgesia has been associated with lengthening of both

first- and second-stage labor as well as slowing of the rate of fetal

descent

� Chorioamnionitis

� infection itself plays a role in the development of abnormal

uterine activity

� Maternal Position during Labor

� recumbency or ambulation during labor

� shorten labor

� decrease rates of oxytocin augmentation

� decrease the need for analgesia

� lower the frequency of operative vaginal delivery

� the uterus contracts more frequently but with less intensity with

the mother in the supine position compared with that of lying on

her side.

� contraction frequency and intensity have been reported to

increase with sitting or standing

� Birthing Position in Second-Stage Labor

� Immersion in Water

Three significant advances in the treatment of uterine dysfunction

� Realization that undue prolongation of labor may contribute to perinatal

morbidity and mortality.

� Use of dilute intravenous infusion of oxytocin in the treatment of certain

types of uterine dysfunction.

� More frequent use of cesarean delivery rather than difficult midforceps

delivery when oxytocin fails or its use is inappropriate.

ACTIVE-PHASE DISORDERS

Classification

� Protraction Disorder (slower than normal)

� Arrest Disorder (complete cessation of progress)

Criteria for Diagnosis of Abnormal Labor Due to Arrest or Protraction Disorders

SECOND-STAGE DISORDERS

� incorporates many of the cardinal movements necessary for the fetus to

negotiate the birth canal

� disproportion of the fetus and pelvis frequently becomes apparent

Duration of 2ND

Stage

� nulliparas - 2 hours

� extended to 3 hours with regional analgesia

� multiparas - 1 hour

� extended to 2 hours with regional analgesia

“Bearing down” or “pushing” – repetitive contraction of the abdominal musculature

with vigor to generate increased intra-abdominal pressure throughout the uterine

contractions �propulsion of the fetus downward

Factors that prevent spontaneous vaginal delivery

� compromised magnitude of the force created by contractions of

abdominal musculature

� heavy sedation or regional analgesia (lumbar epidural or spinal) that

reduces the reflex urge to push, and impair the ability to contract the

abdominal muscles sufficiently

� inherent urge to push is overridden by the intense pain created by bearing

down.

FETOPELVIC DISPROPORTION

� arises from diminished pelvic capacity, excessive fetal size, or more usually,

a combination of both.

Contracted Pelvic Inlet

� shortest anteroposterior diameter is less than 10 cm or

� greatest transverse diameter is less than 12 cm or

� diagonal conjugate of less than 11.5 cm

� Prior to labor, the fetal biparietal diameter averages from 9.5 to as much

as 9.8 cm.

� Cervical dilatation - facilitated by hydrostatic action of the unruptured

membranes or, after their rupture, by direct application of the presenting

part against the cervix

� Membrane rupture � absence of pressure by the head against the cervix

and lower uterine segment � less effective contractions � further

dilatation proceeds very slowly or not at all

� A contracted inlet plays an important part in the production of abnormal

presentations

� In normal nulliparas, the presenting part at term commonly descends into

the pelvic cavity before the onset of labor. In contracted inlet, descent

usually does not take place until after the onset of labor, if at all.

� In women with contracted pelves, face and shoulder presentations are

encountered three times more frequently, and cord prolapse occurs four

to six times more frequently.

Contracted Midpelvis

� more common than inlet contraction

� causes transverse arrest of the fetal head

� interischial spinous diameter is < 8cm

� spines are prominent

� pelvic sidewalls converge

� narrow sacrosciatic notch

� Obstetrical plane of the midpelvis

� extends from the inferior margin of the symphysis pubis through

the ischial spines and touches the sacrum near the junction of the

fourth and fifth vertebrae

A transverse line theoretically connecting the ischial spines divides the midpelvis

into anterior and posterior portions.

� Anterior midpelvis - bounded anteriorly by the lower border of the

symphysis pubis and laterally by the ischiopubic rami

� Posterior midpelvis - bounded dorsally by the sacrum and laterally by the

sacrospinous ligaments

� forms the lower limits of the sacrosciatic notch.

Average midpelvis measurements

� transverse or interspinous = 10.5 cm

� anteroposterior (from the lower border of the symphysis pubis to the

junction of S4–S5) = 11.5 cm

� posterior sagittal (from the midpoint of the interspinous line to the same

point on the sacrum) = 5 cm

Contracted Pelvic Outlet

� interischial tuberous diameter of 8 cm or less

Pelvic outlet likened to 2 triangles:

� Anterior triangle

� base - interischial tuberous diameter

� sides - pubic rami

� apex - inferior posterior surface of the symphysis pubis

� Posterior triangle

� base - interischial tuberous diameter

� no bony sides

� apex - tip of the last sacral vertebra (not the tip of the coccyx).

Estimation of Pelvic Outlet

� X-Ray Pelvimetry

� Computed Tomographic scanning

� Magnetic Resonance

A contracted outlet may cause dystocia through the often-associated midpelvic

contraction

INEFFECTIVE LABOR

Common Clinical Findings in Women with Ineffective Labor

Inadequate cervical dilatation or fetal descent

Protracted labor—slow progress

Arrested labor—no progress

Inadequate expulsive effort—ineffective "pushing"

Fetopelvic disproportion

Excessive fetal size

Inadequate pelvic capacity

Malpresentation or position of fetus

Ruptured membranes without labor

Abnormal Labor Patterns, Diagnostic Criteria, and Methods of Treatment

Criteria for the diagnosis of arrest during first-stage labor (ACOG 1989)

� The latent phase has been completed, with the cervix dilated 4 cm or

more.

� A uterine contraction pattern of 200 Montevideo units or more in a 10-

minute period has been present for 2 hours without cervical change.

CASE:

� L.M., 26 years old, G1P0, was admitted at FEU-NRMF MC due to

hypogastric pain radiating to the lumbosacral area

� AOG: 39-40 wks

� FH: 32 cm

� FHT: 140s bpm

� IE: cervix 2 cm dilated 1cm long, intact BOW, cephalic, station -1

� Uterine contractions: 2-5 min, 50-60 sec, moderate intensity

CASE:

� Labor record:

2 hours later, IE: 3 cm, 1cm long, intact BOW, station -1

Uterine contractions: 2-5 min, 50-60 sec, moderate; FHT: 140

4 hours later, IE: 4 cm, 0.5 cm long, intact BOW, station -1

Uterine contractions: 2-5 min, 50-60 sec, moderate; FHT: 140

Amniotomy was done and revealed clear amniotic fluid

Oxytocin was started

6 hours later, IE: 6 cm, 0.5 cm long, station 0

2-3 mins strong contractions; FHT: 140

8 hours later, IE: 6 cm, 0.5 cm long, station 0

2-3 mins. Strong contractions, FHT: 130

10 hours later, IE: 6 cm, 0.5 cm long, station 0

2-3 mins. Strong contractions, FHT: 130

AP decided to do a Cesarean section

Below is the patient’s labor curve

EFFECTS OF DYSTOCIA

Maternal Effects

� Intrapartum Infection

� Uterine Rupture

� Pathological Retraction Ring

� Pathological retraction ring of Bandl, an exaggeration of the

normal retraction ring

� often the result of obstructed labor

� marked stretching and thinning of the lower uterine segment

� may be seen clearly as a uterine indentation and signifies

impending rupture of the lower uterine segment

� Fistula Formation

� vesicovaginal, vesicocervical, or rectovaginal fistulas

� develops from impaired circulation, necrosis becoming evident

several days after delivery

� Pelvic Floor Injury

� Postpartum Lower Extremity Nerve Injury

� Footdrop - secondary to injury at the level of the lumbosacral

root, lumbosacral plexus, sciatic nerve, or common peroneal

nerve

� most common mechanism of injury, however, is external

compression of the peroneal nerves usually caused by

inappropriate leg positioning in stirrups especially during a

prolonged second stage of labor

� symptoms resolve within 6 months of delivery in most women.

Fetal Effects

� Caput Succedaneum

� Fetal Head Molding

� associated with: nulliparity

oxytocin labor stimulation

delivery with a vacuum extractor

� Skull fractures

Ruptured Membranes Without Labor

� Management: stimulation of contractions when labor did not begin after 6

to 12 hours

PRECIPITOUS LABOR AND DELIVERY

� Definition:

expulsion of the fetus in less than 3 hours

� May result from:

� abnormally low resistance of the soft parts of the birth canal

� abnormally strong uterine and abdominal contractions, or

� rarely, absence of painful sensations and thus a lack of awareness of

vigorous labor

Short labors

� rate of cervical dilatation

� 5 cm/hr for nulliparas

� 10 cm/hr for multiparas

� associated with:

� abruption (20 percent)

� meconium

� postpartum hemorrhage

� cocaine abuse

� low Apgar scores

� multiparity

Maternal Effects

� uterine rupture

� extensive lacerations of the cervix, vagina, vulva, or perineum

� amnionic fluid embolism

� postpartum hemorrhage from uterine atony (hemorrhage from the

placental implantation site )

Seldom are accompanied by serious maternal complications if:

� the cervix is effaced appreciably and compliant

� the vagina has been stretched previously

� the perineum is relaxed

Fetal/Neonatal Effects

� Perinatal mortality and morbidity

� Inappropriate uterine blood flow and fetal oxygenation.

� Intracranial trauma(rare)

� Erb or Duchenne brachial palsy

� Injury from fall

�

Treatment: any oxytocin agents being administered should be stopped

ABNORMAL PRESENTATION, POSITION AND DEVELOPMENT

FACE PRESENTATION

� the head is hyperextended , occiput is in contact with the fetal back and

the chin (mentum) is presenting

� fetal face may present with the chin (mentum) anteriorly or posteriorly,

relative to the maternal symphysis pubis

The occiput is the longer end of the

head lever. The chin is directly

posterior. Vaginal delivery is

impossible unless the chin rotates

anteriorly

Diagnosis

� Vaginal examination

� palpation of the

distinctive facial features

of the mouth and nose,

the malar bones, and

particularly the orbital

ridges

� Radiographic examination

� demonstration of the

hyperextended head with

the facial bones at or

below the pelvic inlet

Etiology

� Marked enlargement of the neck or coils of cord about the neck may cause

extension

� Anencephalic fetuses

� Contracted pelvis

� Very large fetus

� Multiparous women

Mechanism of Labor

� Face presentations rarely are observed above the pelvic inlet

� The brow generally presents, converted into a face presentation after

further extension of the head during descent

� Mechanism of labor consists of the following cardinal movements:

� Descent - brought about by the same factors as in cephalic

presentations

� internal rotation - the objective is to bring the chin under the

symphysis pubis

o results from the same factors as in vertex presentations

� flexion

� accessory movements of extension and external rotation - results

from the relation of the fetal body to the deflected head

Mechanism of labor for right mentoposterior position with subsequent rotation of

the mentum anteriorly and delivery

Management

� In the absence of a contracted pelvis, and with effective labor, successful

vaginal delivery usually will follow

� Cesarean delivery

� Because face presentations among term-size fetuses are more

common when there is some degree of pelvic inlet contraction,

cesarean delivery frequently is indicated.

BROW PRESENTATION

� Rarest presentation because it is

unstable and often converts to a

face or occiput presentation

� The portion of the fetal head

between the orbital ridge and

anterior fontanel presents at the

pelvic inlet

� The fetal head thus occupies a

position midway between full

flexion (occiput) and extension

(mentum or face)

� Only transient prognosis depends

on the ultimate presenting part

� Causes and etiology are the same

as of the face presentation

� Management is the same as those

for a face presentation

Brow Posterior Presentation

Diagnosis

� Abdominal palpation - when both the occiput and chin can be palpated

easily

� Vaginal examination – palpation of the frontal sutures, large anterior

fontanel, orbital ridges, eyes, and root of the nose

Mechanism of Labor

� very small fetus and a large pelvis - labor is generally easy

� with a larger fetus - usually difficult, because engagement is impossible

until there is marked molding that shortens the occipitomental diameter

or, more commonly, until there is either flexion to an occiput presentation

or extension to a face presentation

TRANSVERSE LIE

� the long axis of the fetus is approximately perpendicular to that of the

mother

� referred to as shoulder or acromnion presentation

� the shoulder is usually on the pelvic inlet, with the head lying on one iliac

fossa and the breech in another

Diagnosis

� Abdominal examination

� abdomen is unusually wide, whereas the uterine fundus extends

to only slightly above the umbilicus.

� no fetal pole is detected in the fundus, ballottable head is found

in one iliac fossa and the breech in the other

� back up (anterior) - a hard resistance plane extends across the

front of the abdomen

� back down (posterior)- irregular nodulations representing the

small parts are felt through the abdominal wall.

� Vaginal examination

� early stages of labor: the side of the thorax or the "gridiron" feel

of the ribs

� Advanced labor: the scapula and clavicle are palpated

Etiology

� Abdominal wall relaxation from high parity.

� Preterm fetus.

� Placenta previa.

� Abnormal uterine anatomy.

� Excessive amnionic fluid.

� Contracted pelvis.

Palpation in transverse lie, right acromidorsoanterior position. A. First maneuver. B.

Second maneuver. C. Third maneuver. D. Fourth maneuver.

Neglected shoulder presentation. A thick muscular band forming a

pathological retraction ring has developed just above the thin lower uterine

segment. The force generated during a uterine contraction is directed centripetally

at and above the level of the pathological retraction ring. This serves to stretch

further and possibly to rupture the thin lower segment below the retraction ring.

(P.R.R. = pathological retraction ring.)

Mechanism of Labor

� Spontaneous delivery of a fully developed newborn is impossible with a

persistent transverse lie

� rupture of the membranes�the fetal shoulder is forced into the pelvis

corresponding arm frequently prolapses�shoulder is arrested by the

margins of the pelvic inlet ( head in one iliac fossa and the breech in the

other) �impacted shoulder �neglected transverse lie �uterine rupture

� If the fetus is small—usually less than 800 g—and the pelvis is large,

spontaneous delivery is possible despite persistence of the abnormal lie

Management

� In general, the onset of active labor in a woman with a transverse lie is an

indication for cesarean delivery

� Because neither the feet nor the head of the fetus occupies the lower

uterine segment, a low transverse incision into the uterus may lead to

difficulty in extraction of a fetus entrapped in the body of the uterus above

the level of incision. Therefore, a vertical incision is likely to be indicated

OBLIQUE LIE

� called an unstable lie

� when the long axis forms an acute angle

� usually only transitory, because either a longitudinal or transverse lie

commonly results when labor supervenes

COMPOUND PRESENTATION

� an extremity prolapses alongside the presenting part, with both presenting

in the pelvis simultaneously

The left hand is lying in

front of the vertex. With

further labor, the hand

and arm may retract from

the birth canal and the

head may then descend

normally.

Causes

� conditions that prevent complete occlusion of the pelvic inlet by the fetal

head, including preterm birth

Prognosis and Management

� Perinatal loss is increased as a result of concomitant preterm delivery,

prolapsed cord, and traumatic obstetrical procedures

� In most cases, the prolapsed part should be left alone, because most often

it will not interfere with labor

� Prolapsed arm alongside the head close observation to ascertain whether

the arm retracts out of the way with descent of the presenting part, if it

fails to retract and if it appears to prevent descent of the head, the

prolapsed arm should be pushed gently upward and the head

simultaneously downward by fundal pressure�vaginal delivery

PERSISTENT OCCIPUT POSTERIOR POSITION

� Transverse narrowing of the midpelvis is undoubtedly a contributing factor

� Usually undergo spontaneous anterior rotation followed by uncomplicated

delivery

Occiput posterior presentation in early labor compared with presentation at delivery.

Ultrasonography was used to determine position of the fetal head in early labor.

� The possibilities for vaginal delivery are:

� Spontaneous delivery

� Forceps delivery with the occiput directly posterior

� Manual rotation to the anterior position followed by spontaneous

or forceps delivery

� Forceps rotation of the occiput to the anterior position and

delivery

PERSISTENT OCCIPUT TRANSVERSE POSITION

� Most likely a transitory one because the occiput tends toward the anterior

position in the absence of a pelvic architecture abnormality

� Spontaneous anterior rotation usually is completed rapidly, thus allowing

the choice of spontaneous delivery or delivery with outlet forceps.

Delivery

� If rotation ceases because of poor expulsive forces and pelvic contractures

are absent, vaginal delivery usually can be accomplished

� The occiput may be manually rotated anteriorly or posteriorly and forceps

delivery performed from either the anterior or posterior position

Delivery

� Application of Kielland forceps to the fetal head to rotate the occiput to

the anterior position, and then deliver the head either with the same

forceps or with Simpson or Tucker–McLane forceps

� Oxytocin may be infused and closely monitored

With the platypelloid (anteroposteriorly flattened) and the android (heart-shaped)

pelves, there may not be adequate room for rotation of the occiput to either the

anterior or the posterior position.

SHOULDER DYSTOCIA

� neonates experiencing shoulder dystocia had significantly greater

shoulder-to-head and chest-to-head disproportions compared with those

of equally macrosomic newborns delivered without dystocia

� Most cases of shoulder dystocia cannot be accurately predicted or

prevented.

� Elective induction of labor or elective cesarean delivery for all women

suspected of carrying a macrosomic fetus is not appropriate.

� Planned cesarean delivery may be considered for the nondiabetic woman

carrying a fetus with an estimated fetal weight exceeding 5000 g or the

diabetic woman whose fetus is estimated to weigh more than 4500 g.

Maternal Consequences

� Postpartum hemorrhage - usually from uterine atony, vaginal and cervical

lacerations

Fetal Consequences

� Fetal morbidity and mortality

� Brachial Plexus Injury

� Clavicular fracture

� Humeral fracture

Maternal Risk factors

� Obesity

� Multiparity

� Diabetes Mellitus

Management

� Reduction in the interval of time from delivery of the head to delivery of

the body is of great importance to survival

� An initial gentle attempt at traction, assisted by maternal expulsive efforts,

is recommended

� Large episiotomy

� Adequate analgesia is ideal

Techniques to free the anterior shoulder from its impacted position beneath the

symphysis pubis:

� Moderate suprapubic pressure

� can be applied by an assistant while downward traction is applied

to the fetal head.

� McRoberts maneuver

� consists of removing the legs from

the stirrups and sharply flexing

them up onto the abdomen

� caused straightening of the sacrum

relative to the lumbar vertebrae,

rotation of the symphysis pubis

toward the maternal head, and a

decrease in the angle of pelvic

inclination

� pelvic rotation cephalad tends to

free the impacted anterior shoulder

� reduced the forces needed to free

the fetal shoulder.

The McRoberts maneuver. The maneuver consists of removing the legs from the

stirrups and sharply flexing the thighs up onto the abdomen, as shown by the

horizontal arrow. The assistant is also providing suprapubic pressure simultaneously

(vertical arrow).

� Woods corkscrew maneuver

� The hand is placed

behind the posterior

shoulder of the fetus

and progressively

rotating the posterior

shoulder 180 degrees in

a corkscrew fashion so

the impacted anterior

shoulder could be

released

� Delivery of the posterior shoulder consists of carefully sweeping the

posterior arm of the fetus across the chest, followed by delivery of the

arm. The shoulder girdle is then rotated into one of the oblique diameters

of the pelvis with subsequent delivery of the anterior shoulder

Shoulder dystocia with impacted

anterior shoulder of the fetus.

A.The operator's hand is

introduced into the vagina along

the fetal posterior humerus, which

is splinted as the arm is swept

across the chest, keeping the arm

flexed at the elbow.

B. The fetal hand is grasped and

the arm extended along the side of

the face.

C. The posterior arm is delivered

from the vagina

� Rubin’s maneuver

� the fetal shoulders are rocked from side to side by applying force

to the maternal abdomen.

� the pelvic hand reaches the most easily accessible fetal shoulder,

which is then pushed toward the anterior surface of the chest

The second Rubin maneuver.

A. The shoulder-to-shoulder diameter is

shown as the distance between the two

small arrows.

B. The more easily accessible fetal

shoulder (the anterior is shown here) is

pushed toward the anterior chest wall

of the fetus. Most often, this results in

abduction of both shoulders, reducing

the shoulder-to-shoulder diameter and

freeing the impacted anterior shoulder.

� Deliberate fracture of the clavicle

� pressing the anterior clavicle against the ramus of the pubis to

free the shoulder impaction

� Hibbard Maneuver

� pressure is applied to the fetal jaw and neck in the direction of the

maternal rectum, with strong fundal pressure applied by an

assistant as the anterior shoulder is freed

� Zavanelli maneuver

� cephalic replacement into the pelvis and then cesarean delivery.

� Cleidotomy

� cutting the clavicle with scissors or other sharp instruments

� usually used for a dead fetus

� Symphysiotomy

Shoulder dystocia drill

1. Call for help—mobilize assistants, an anesthesiologist, and a pediatrician. Initially,

a gentle attempt at traction is made. Drain the bladder if it is distended.

2. A generous episiotomy (mediolateral or episioproctotomy) may afford room

posteriorly.

3. Suprapubic pressure is used initially by most practitioners because it has the

advantage of simplicity. Only one assistant is needed to provide suprapubic

pressure while normal downward traction is applied to the fetal head.

4. The McRoberts maneuver requires two assistants. Each assistant grasps a leg and

sharply flexes the maternal thigh against the abdomen.

belle ens ‘09