‫‪MECHANISM OF LABOR‬‬
‫‪ABNORMAL‬‬
‫‪PRESENTATION AND‬‬
‫‪BREECH‬‬
‫محاضره مهمه جدا – بالنظري‬
‫وباالوسكي‬
‫‪DR. AHMED ABDULWAHAB‬‬
‫‪Assistant‬‬
‫‪Professor,‬‬
‫شرح‬
‫‪ –Consultant‬هي لم ت‬
‫يوجد ملف مرفق فيه عمليه الوالده بالتفصيل‬
‫بالمحاضره ولكنها شرحت بالكلينيكال سكيلز وهي مهمه‬
‫جدا‪OBGYN‬‬
‫‪Department‬‬
‫جدا – ارجوا قراءتها – بالنسبه لالسئله النظريه المحاضره هذي‬
‫كافيه‬
 Vaginal delivery necessitates the
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accommodation of the fetal head to the bony
pelvis.
1- bony pelvis :
In women the pelvis has special form that
adapts to childbearing .
It is composed of four bones :
The sacrum coccyx and two innominate
bones ..
The innominate bone ‫ عظم الحوض‬is is
formed by the fusion of the ilium ,ischium,
 The true pelvis is the portion importatnt in
childbearing is bounded above by promontory
and alae of the sacrum the linea terminalis and
the upper margin of the pubic bone , and
below by the pelvic outlet .
 Ischial spines are of great obstetrical
importance because it is the shortest pelvic
diameter and has a valuable landmarks in
assessing the level of the presenting part of
the fetus
 The sacrum form the posterior
wall of the pelvis and it is curved to
accommodate the rotating head .
 The promontory may be felt on
vaginal examination and provide a
landmark for clinical pelvimetry 
‫مهم جدا – يقاس عرض الحوض ( اكلينيكيا حسب‬
‫الطريقه المكتوبه باالعلى ) ويقاس راس الجنين ليحدد‬
‫امكانيه الوالده الطبيعيه من عدمها‬
Pelvic Inlet The pelvic inlet has five important diameters. The anteroposterior diameter is
described by one of two measurements.
1- The true conjugate (anatomic conjugate) is the anatomic diameter and extends from the
middle of the sacral promontory to the superior surface of the pubic symphysis.
2- Theobstetric conjugate represents the actual space available to the fetus and extends from
the middle of the sacral promontory to the closest point on the convex posterior surface of the
symphysis pubis.
3- The transverse diameter is the widest distance between the iliopectineal lines. Each oblique
diameter extends from the sacroiliac joint to the opposite iliopectineal eminence.The posterior
sagittal diameter extends from the anteroposterior and transverse intersection to the middle
of the sacral promontory.
 Pelvic inlet measurement ‫ملخص لما‬
‫سبق‬:
 Diagonal conjugate it is the distant from
the sacral poromontory to the lower
margin of the symphysis pubis.
 True conjugate from sacral promotory
to upper border of symphysis pubis
 Obstetric conjugate from sacral
promontory to mid of posterior aspect
of symphysis pubis subtract 1.5-2.0 cm from
diagonal conjugate
 The mid pelvis at the level of
ischial spines the interspinous
diameter is 10 cm .
 Pelvic outlet clinically it is the
distant between the ischial
tuberosities it is around 8.0 cm
2- THE FETAL SKULL
 BONES
 Two frontal bones separated by frontal suture.
 Two parietal bones separated by sagittal suture .
 Two coronal sutures between frontal and
parietal bones .
 Two lambdoid sutures between parietal and and
occipital bone .
 Sutures meet at an irregular space forms which is
enclosed by a membrane called fontanel .
 Anterior fontanel is a lozenge shape between the
two frontal and two parietal bones usually it is
opened .
 Posterior fontanel at the junction of the two
parietal bones and occipital bone .
 It gives an important information concerning
presentation and position of the fetus.
‫مهمه جدا‬

Diameters : Several diameters of the fetal skull are important

The anteroposterior diameter presenting to the maternal pelvis depends on the degree
of flexion or extension of the head and is important because the various diameters differ
in length.

The following measurements are considered average for a term fetus:

Suboccipitobregmatic (9.5 cm), the presenting anteroposterior diameter when the head
is well flexed, as in an occipitotransverse or occipitoanterior position; it extends from the
undersurface of the occipital bone at the junction with the neck to the center of the
anterior fontanelle.

Occipitofrontal (11 cm), the presenting anteroposterior diameter when the head is
deflexed, as in an occipitoposterior presentation; it extends from the external occipital
protuberance to the glabella.

Supraoccipitomental (13.5 cm), the presenting anteroposterior diameter in a brow
presentation and the longest anteroposterior diameter of the head; it extends from the
vertex to the chin.

Submentobregmatic (9.5 cm), the presenting anteroposterior diameter in face
presentations; it extends from the junction of the neck and lower jaw to the center of the
anterior fontanelle.

The transverse diameters of the fetal skull are as follows:Biparietal (9.5 cm), the largest
transverse diameter; it extends between the parietal bones.

Bitemporal (8 cm), the shortest transverse diameter; it extends between the temporal
bones
 : ‫الساليدين القادمه ملخص لما سبق‬
 Fetal head diameters
 Subocipotobregmatic 9.5 cm called : vertex
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presentation.  the baby has flexed head 
the perfect position for delivery
Submentobregmatic 9.5 cm called : face
presentation ( ‫وضع والده سيشرح اخر‬
‫ وضع غير مناسب‬- ) ‫المحاضره‬.
Mentovertical 12.5 called : brow presentation
. - ) ‫وضع والده سيشرح اخر المحاضره‬
‫وضع غير مناسب‬
Biparietal diameter 9.5cm .
Occiptofrontal 10.5 cm
 How to detrmine the presentation ?
 By looking for the landmarks as following : (
MCQ )
 You can feel :
 Occipital bone is the landmark in vertex
presentation.
 Mentum is landmark for face presentation,
 Frontal bone is land mark for brow
presentation
Labour
‫موضوع مهم جدا باالختبار العملي والنظري‬
Definition.
It is the onset of painful, regular,contractions,
more than one every ten minutes. With
progressive cervical effacement and dilatation
accompanied by descend of the fetal
presenting part.
Stages of labor
Labor is divided in to three stages.
1st stage from diagnosis of labor till full dilatation
of the cervix.
2nd stage of labor from full dilatation of the
cervix till delivery of the fetus.
3rd stage from delivery of the fetus until delivery
of the placenta.
‫يوجد ملف مرفق فيه عمليه الوالده بالتفصيل – هي لم تشرح‬
‫بالمحاضره ولكنها شرحت بالكلينيكال سكيلز وهي مهمه جدا‬
‫جدا – ارجوا دراستها‬
The duration of labor
Primigravida ‫ البكر – اول مره‬about 12 hours .
Multigravida 8.0 hours
The moral of most women deteriorate if labor
is prolonged .
There is greater incidence of fetal hypoxia after
long labor.
Greater incidence of operative vaginal delivery
( vacuum or forceps ) .
NB / the contraction in labor is on and off so it
allow the O2 and nutritious to pass to the fetus
Mechanisim of labor
It is a series of changes in position and attitude
that the fetus undergoes during its passage
through the birth canal.
ENGAGEMENT.
It is when the widest diameter of the head has
passed successfully through the inlet that is
when the biparietal diameter passed to the
level of the ischial spines
MECHANISM OF LABORS : Six movements of the baby enable
it to adapt to the maternal pelvis: descent, flexion, internal
rotation, extension, external rotation, and expulsion . These
movements are discussed here for both an occipitoanterior
and occipitoposterior position at engagement. The other
positions will be covered at the end of the lec. :
6 movements :
1- DESCENT.
It is secondary to uterine action in 1st and early phase of 2nd
stage of labor .
‫ الكاتب‬: Descent is brought about by the force of the uterine
contractions, maternal bearing-down (Valsalva) efforts, and,
if the patient is upright, gravity.
2- FLEXION
When the head descent to the narrow mid cavity flexion should
occur.
‫ الكتاب‬: Partial flexion exists before labor as a result of the natural
muscle tone of the fetus. During descent, resistance from the cervix,
walls of the pelvis, and pelvic floor cause further flexion of the
cervical spine, with the baby's chin approaching its chest. In the
occipitoanterior position, the effect of flexion is to change the
presenting diameter from the occipitofrontal to the smaller
suboccipitobregmatic . In the occipitoposterior position, complete
flexion may not occur, resulting in a larger presenting diameter,
which may contribute to a longer labor.
3- INTERNAL ROTATION .
The shape of the bony pelvis and direction of the
pelvic floor muscles in addition to the well flexed
head will help the head to rotate the head into
the occipito anterior position .
In a well flexed head the occipit will meet the pelvic
floor and will guide the direction of the rotation
‫ الكتاب‬: In the occipitoanterior positions, the fetal head, which enters the pelvis
in a transverse or oblique diameter, rotates so that the occiput turns anteriorly
toward the symphysis pubis. Internal rotation probably occurs as the fetal head
meets the muscular sling of the pelvic floor. It is often not accomplished until the
presenting part has reached the level of the ischial spines (zero station) and
therefore is engaged. In the occipitoposterior positions, the fetal head may
rotate posteriorly, so the occiput turns toward the hollow of the sacrum.
4- EXTENSION.
The head is deliver by extension first the bregma
,face , and chin appear in succession over the
posterior vaginal opening and perineal body
‫مواجه لالرض‬
‫ الكتاب‬: The flexed head in an occipitoanterior position continues to descend within
the pelvis. Because the vaginal outlet is directed upward and forward, extension
must occur before the head can pass through it. As the head continues its
descent, there is bulging of the perineum followed by crowning. Crowning occurs
when the largest diameter of the fetal head is encircled by the vulvar ring. At this
time, the vertex has reached station +5. When necessary, an incision in the
perineum (episiotomy) may aid in reducing perineal resistance, although current
management is to allow the fetus to deliver without an episiotomy. The head
is born by rapid extension as the occiput, sinciput, nose, mouth, and chin pass
over the perineum.
In the occipitoposterior position, the head is born by a combination of flexion and
extension. At the time of crowning, the posterior bony pelvis and the muscular
sling encourage further flexion. The forehead, sinciput, and occiput are born as
the fetal chin approaches the chest. Subsequently, the occiput falls back as the
head extends, and the nose, mouth, and chin are born..
RESTITUTION.
As soon as the head escape from the vulva
the head aligns itself with the shoulder
5- EXTERNAL ROTATION.
In order to deliver the shoulders have to rotate
into the direct anterior- posterior plane .
The doctor will rotate the head making the face
of the fetus looking to medial aspect of the
maternal thigh .
‫ الكتاب‬: In both the occipitoanterior and occipitoposterior positions,
the delivered head now returns to its original position at the time of
engagement to align itself with the fetal back and shoulders. Further
head rotation may occur as the shoulders undergo an internal rotation to
align themselves anteroposteriorly within the pelvis.
 6- EXPULSION : Following external rotation
of the head, the anterior shoulder delivers
under the symphysis pubis, followed by the
posterior shoulder over the perineal body and
the body of the child.
Delivery of the shoulders .
The anterior shoulder is under the
symphysis pubis and deliver first
,and the posterior shoulder deliver
Subsequently
If the shoulders does not delivered the
situation called (( shoulder dystonia ))
 which is Emergency situation
THIRD STAGE OF LABOR .
Separation of the placenta occurs because of the reduction
of the volume of the uterus due to the uterine contraction
and retraction
Separation of the placenta generally occurs within 2 to 10
minutes of the end of the second stage of labor.
Signs of placental separation are as follows: (1) a fresh show of
blood from the vagina, (2) the umbilical cord lengthens
outside the vagina, (3) the fundus of the uterus rises up, and
(4) the uterus becomes firm and globular.
MALPRESENTATIONS ( abnormal presentations
( positions ) of the fetuses

Fetal Malpresentation : The term malpresentation encompasses any fetal
presentation other than vertex, including breech, face, brow, shoulder, and
compound presentations. Both fetal and maternal factors contribute to the
occurrence of malpresentation. The most common malpresentation is breech.
 Some IMP dif :
 Fetal lie . : This is the relationship of the
longitudinal axis of the fetus to longitudinal axis of
the mother.
 There are three lies longitudinal ‫ الطبيعي‬, oblique
, and transverse lie . ‫مهمه جدل‬
 Fetal attitude , this is the relationship of the
different parts of the baby to each others , usually
flexion attitude .
 Presentation. : It is which part of the fetus
occupies the pelvis eg ,cephalic , breech ,
shoulder presentation .
 Position . : It is the relationship of the
presenting part to the four pelvic quadarents
.eg left occipito anterior , right mento
posterior .
Remember
 Subocipotobregmatic 9.5 cm called : vertex
presentation.  the baby has flexed head 
the perfect position for delivery
 Submentobregmatic 9.5 cm called : face
presentation (.
 Mentovertical 12.5 called : brow presentation
‫ اوال‬: BREECH PRESENTATION
 Baby is presenting with buttocks and legs and
incidence is 3% at term . ( most common
malpresentation )
 Types .
 Complete breech where the leg are flexed at hip
joint and knee joint ,
 Frank breech flexed hip but extended knee joint .
 Footling breech ( worst type ) with extended hip
and knee joints and high buttocks .  need C
section
 Fetal causes .
 Hydrocephalas , poly hydramnios
oligohydramnios , placenta previa , short
umbilical cord .
 Maternal causes .
 Uterine anomalies, fibroid uterus, small pelvis
 The most important cause is preterm labor
‫مهمه – سؤال‬
MANAGEMENT
 The patient can be offered the option of either : vaginal breech
delivery , caesarian section or external cephalic version . ‫مهم‬
: ‫تفاصيل‬
1- External cephalic version ‫ لف الجنين يدويا من الخارج‬ECV: .
Done after 38 weeks.
Contra indications : ‫ مهمه‬:
Contracted pelvis , scar uterus, placenta previa , hypertensive
patient .
 Complications : ‫مهمه‬
 Membrane rupture , uterine rupture, abruptio placenta , cord
prolapse

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 Cont.
 It should be done in the theater with every
thing ready four c/s . ‫مهمه‬
 If blood group is rhesus negative should
receive anti D immunoglobulin
 2- vaginal delivery :
 Complications of vaginal breech delivery :
 Cord prolaps , lower limb fracture , abdominal
organs injuries , brachial plexus nerve injuries,
 Difficulties in delivering the head ( the head
could traps (( emergency )) and intracranial
bleeding .
Management of breech
delivery ‫مهمه جدا باالوسكي‬
 Patient in lithotomy position ,
 Cervix should be fully dilated .
 When buttocks protrudes through the vulva an
episiotomy should be performed .
 Legs are delivered easily unless it is an extended
that need to be flexed .
 With delivery of the umbilicus small loop of cord
is pulled down to feel the pulsations .
 Then delivery of both arms first the anterior then
the posterior .
 Delivery of the head .
 Keep the baby hanging to promote head
flexion ( Burn Marshal) manoeuvre . ‫مهمه‬
 Jaw flexion shoulder traction . ‫مهمه‬
 Obstetrical forceps for the after coming head.
‫مهمه‬
‫ ثانيا‬: Face presentation
 Incidence 1-500 .
 Occurs as the result of complete extension of
the head .
 Submentobregmatic 9.5 cm
 In majority of case the cause is unknown but
is frequently attributed to excessive tone of
the extensor muscles of the fetal neck.
 Rare causes like tumor of the neck , thyroid ,
thymus gland and cord around the neck
 The presenting diameter of the face is the
submento –bregmatic , which measures 9.5
cm .
 Diagnosed in labor by palpating the nose,
mouth ,and the eyes on vaginal examination.
 In case of mento-anterior vaginal delivery is
possible and the head is delivered by flexion.
‫مهمه‬
 If the face is mento posterior the delivery is
not possible and patient should be delivered
by caesarian section. ‫مهمه‬
‫ ثالثا‬: Brow presentation
 Incidence is 1-2000.
 It occurs when there is less extension of the
fetal head than that seen in face
presentation, mid way between face and
vertex presentation .
 The presenting diameter is mento-vertical
13.5 cm. ‫مهمه‬
 Is diagnosed in labor by palpating the anterior
fontanelle ,supra orbital ridges, and nose on
vaginal examination .
 Delivery is by caesarian section. – ‫مهمه جدا‬
‫ رابعا‬: Shoulder presentation
 It due to oblique or transverse lie in labor .
 Common in women with high parity .
 Also occurs in placenta previa , uterine
anomalies , pelvic tumor.
 If diagnosed in early labor with intact membrane
and no other pathology external cephalic version
can be tried .
 In case of rupture of the membranes exclude
cord prolaps .
 Delivery of shoulder presentation in labor with
rupture membrane is by caesarian section.