Mechanism of labor abnormal presentation and breech

DR. AHMED ABDULWAHABAssistant Professor, ConsultantOBGYN Department

محاضره مهمه جدا – بالنظري وباالوسكي

يوجد ملف مرفق فيه عمليه الوالده بالتفصيل – هي لم تشرح بالمحاضره ولكنها شرحت بالكلينيكال سكيلز وهي مهمه جدا جدا – ارجوا قراءتها – بالنسبه لالسئله النظريه المحاضره

هذي كافيه

Vaginal delivery necessitates the 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 الحوض is is

formed by the fusion of the

ilium ,ischium, and pubis

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.

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

مهمه جدا

: الساليدين القادمه ملخص لما سبق Fetal head diameters Subocipotobregmatic 9.5 cm called :

vertex 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

dilatationaccompanied by descend of the fetalpresenting 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 مره about 12 hours .Multigravida 8.0 hoursThe 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 .

Descent is brought about by the force of the : الكاتبuterine 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.

Partial flexion exists before labor as a result of : الكتابthe 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

In the occipitoanterior positions, the fetal head, which enters the pelvis in : الكتابa 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

The flexed head in an occipitoanterior position continues to descend : الكتابwithin 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 .

In both the occipitoanterior and occipitoposterior : الكتابpositions, 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 thesymphysis pubis and deliver first,and the posterior shoulder deliverSubsequently

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

BREECH PRESENTATIONاوال : 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 الخارج

ECV: . 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

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

Face presentation ثانيا : 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

Brow presentationثالثا : 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 – الحل الوحيد

Shoulder رابعا : 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.