16. Cephalic presentation – brow , face and chin. Mechanism of delivery and management Flashcards
the fetal skull has how many different parts ?
cranium
face
base
describe the base of the skull in a baby ?
base of the skull has large, ossified, firmly united, and noncompressible bones.
This serves to protect the vital structures contained within the brain stem.
what are the specific bones in the cranium ?
the occipital bone posteriorly,
two parietal bones bilaterally,
two frontal
two temporal bone
describe the cranial bones ?
The cranial bones at birth are thin, weakly ossified, easily compressible, and
interconnected only by membranes (know as sutures)
These features allow them to overlap under pressure and to change shape to conform to the maternal pelvis, a process known as “molding
where does the sagittal suture lie ?
The sagittal suture lies between the parietal bones and extends in
an anteroposterior direction between the fontanelles, dividing the head into
right and left sides.
where does the lamboid suture lie ?
from the posterior fontanelle laterally and serves to separate the occipital from the parietal bones.
where does the coronal suture lie ?
The coronal suture extends from the anterior fontanelle laterally and serves to
separate the parietal and frontal bones.
where does the frontal suture lie
lies between the frontal bones extends from the anterior
fontanelle to the glabella
the two frontal bones only fuse between 3-9 months of age
what is the fontelle ?
the point where the sutures intersect are known as fontanelles, the most important of which are the anterior and posterior fontanelles
when does the posterior fontanelle close ?
closes at 6 to 8 weeks after birth
when does the anterior fontanelle close ?
anterior fontanelle does not become ossified until about 18 months
why does the anterioir fontanelle close after such long time
allows the skull to accommodate the tremendous growth of the infant’s brain
after birth
cephalic presentation can be classified into ?
vertex
face /chin
brow
oskie
describe vertex presentation ?
the head is flexed and the occiput leads the way
what are the subclassifications for vertex presentation ?
the vertex presentation is further classified into
right , left occipitoanterioir
right/ left occipital transverse
right /left/straight occipitoposterioir
why is occiput anterior ideal ?
optimal for extension
why is occipitoposterior not ideal ?
describe the mechanism of labour
labour becomes more prolonged - require forceps , vacuum extraction or c section
vertex is deflexed and the ocipitofrontal dimatere is the engaging diamter which is 11.5cm
partially deflexed suboccipitofrontal diameter = 10.5
favourable - same first three cardinal movement - FLEXION IS IMPORTANT HEAVILY to get subocipitobregamatic = 9.5 cm
the direction of the pelvic floor muscles is downwards forwards and medially undergoes long internal rotation = 3/8
and then as in normal labour continues
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unfavourable
delayed engagement and deflexion persists
mild of deflexion + android pelvis
the occiput is lower than the sinciput
when reaching the ischial spines completion of internal rotation is not possible only 1/8 because theischial spines are prominent and the pelvis is narrow =deep transverse arrest
contracted gynecoid pelvis - moderate deflexion persists
the occiput and the sinciput will be at the same level
no internal rotation = persistent ocipitoposterioir position = oblique posterioir arrest
what predisposes face presentation ?
Multiparity with pendulous abdomen
Contracted pelvis
Flat pelvis
pelvic tumors
fetal
anencephaly
prematurity ,
macrosomia ,
face presentations are classified according to the position of the ?
mentalis
what are the sub classification of face presentation
left/right mento anterior
left/right mento posterior
left/right mento transverse
most common position is left mentoanterior
which of the sub classification of face presentation cannot be delivered vaginally ? and why?
PERISTANT left/right mento posterior
cardinal movements in the mechanism of mento- posterior positions are like those of occipitoposterior position
differentiating features are—(1) In the mentoposterior position, anterior rotation of the mentum occurs in only 20–30% cases.
In the rest, incomplete anterior rotation, nonrotation or short posterior rotation
Arrest occurs in all these positions with average size pelvis and fetalhead. Unlike persistent occipitoposterior, where occasional face-to-pubis delivery occurs
This is because the relatively short neck (5cm) cannot clear off the total length of the sacrum (12 cm). As such the thorax is thrust in, resulting bregmaticosternal diameter (18 cm ) to occupy the pelvis - obstructed labour
what is brow presentation ?
the fetal head is midway between full flexion
the presenting part is between the orbital ridge and the anterior fontanelle.
hence the mentovertical dimatere is the presenting diameter which is much larger than vertex or face presentation
the submentobregmatic diameter is how long ?
9.5cm
junction of the neck and lower jaw to centre of anterior fontanelle
submentobregmatic diameter is for which presentation ?
face presentation
anteroposterior diametre when the head is flexed in vertex labour ?
suboccipitobregmatic -9.5cm
engagement diameter in occipito-anterior with complete flexion.
what causes brow presentation ?
same as face presentation
especially in flat pelvis
mechanism of labour in face presentation ?
principle movements those corresponding to occipiotanterioir
exception to increasing extension instead of flexion and delivery is by flexion of the head not extension
the course of left mento anterior and right mentoanterioir - which is usual
Descend
engagement - it is delayed
and descend with increasing extension occurs till chin touches pelvic floor
Descent with increasing extension occurs till the chin touches the pelvic floor.
internal rotation - 1/8th anteriorly placing the mentum behind the symphysis pubis
further descend till the submentum hinges at pubic arch
delivery of the head - is by flexion
delivering the chin , face , brow and lastly occiput
Restitution occurs through 1/8th of a circle opposite to the direction of internal rotation.
External rotation occurs further 1/8th of circle to the same side of restitution so that ultimately the face looks directly to the thigh
diagnosis of face presentation ?
antenatal leopold
mentoanterior
lateral grip : fetal limbs felt anteriorly
back and flank difficult to palpate
mentoposterioir lateral grip
back is felt
mentoanterioir
pelvic grip
>cephalic prominence to the side which back lies and the transverse groove between head and back not so prominent in anterior but prominent in mento posterior
> The head feels very big and is nonengaged.
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vaginal examinations - often confused for breech
however distinguished when
the malar eminence and the lips are not in line
but in breech the the anus and the ischial tuberosities are in line
sucking effect on mouth
hard alveolar margins and absence of meconium
The mentum and the mouth should be clearly identified to exclude brow presentation and to identify the position.
sonography to confirm
what is complications of face presentation
n spite of the fact that the engaging diameter of the head in flexed vertex and the extended face presentation is the same—9.5 cm
rupture he membrane earlier than normal
more risk of cord prolapse
delay of labour -due to
1) weak uterine contractions 2) absence of molding of face so edema of face and ocipitofrontal diameter elongates
3) arrest at times and late internal rotation
increase chance of perineal damage
pph - atony uterus and perineallacerations
diagnosis brow presentation :
antenatal diagnosis rarely made the through leopard the results is more r less like face presentation
antenatal leopold manuevers - cephalic prominence and transverse groove less prominent and
The head feels very big and is nonengaged.
vaginal examination - palpation of supraorbital ridges and anterior fontanelle
sonography to confirm
mechanism of brow delivery ?
ONLY C SECTION
Diameter of engagement is through the oblique diameter with the brow anterior or posterior.
the engaging diameter of the head is mentovertical -13.5 cm
it is longer than the largest diameter of the pelvic brim.
NO mechanism of labour in an average size baby with a normal pelvis
but if the baby is small and the pelvis is big enough with good uterine contractions delivery can occur in MENTOANTERIOIR POSITION
brow descends until it touches the pelvic floor
internal rotation
the root of the nose hinges under the symphysis pubis
brows delivered by flexion
followed by extension to deliver the face
then usual restitution external rotation
what is persistent ocipitoposterioir presentation?
malposition not malpresentation
diagnosis of ocipitoposterioir
Umbilical grip:
(1) The fetal limbs are more easily felt near the midline on either side. (2) The fetal back is felt far away from the midline on the flank and often difficult to outline clearly. (3) The anterior shoulder lies far away from the midline.
pelvic grip are: (1) The head is not engaged. (2) The cephalic prominence (sinciput) is not felt so prominent as found in well-flexed occipitoanterior.
The DIAMOND anterior fontanel is felt more easily because of deflexion of the head and at times
ear is to be located and unfolded pinna points toward the occiput.
management of ocipitoposteroir
Occipitoposterior per se is not an indication of cesarean section. Pelvic inadequacy or its unfavorable , along with obstetric complications such as, preeclampsia, postcesarean pregnancy, big baby usually need cesarean section
Station of the head, (2) Position of the sagittal suture and the occiput, (3) Degree of deflexion of the head, (4) Degree of molding and caput formation
if Weak pain, persistence of deflexion and nonrotation of the occiput = start oxytocin
non rotation :oblique posteriorior
to be noted all of the above +
ssessment of the pelvis at and below the level of obstruction, i.e. ischial spines, side walls of the pelvis,ubic arch and transverse diameter of the outlet.
Ventouse :
pelvis is adequate and the non- rotation of the occiput is either due to weak contractions or lack of tone of pelvic floor muscles.
(2) Cesarean section:
Manual rotation followed by forceps extraction:
kielland forcep rotation and extraction
causes of occipitoposterior presentation?
The shape of the pelvis: anthropoid and android pelvis
Maternal kyphosis
describe management of face presentation ?
MENTO ANTERIOIR
One should wait for spontaneous delivery to occur. Perineum should be protected with liberal mediolateral episiotomy. In case of delay, forceps delivery is done.
MENTOPOSTERIOIR
in second stage -
if anterior rotation of the chin occurs, spontaneous or forceps delivery with episiotomy
(2) In incomplete or malrotation
c section
what are the complications in brow presentation?
obstructed labor. It is an important cause of rupture of uterus in multiparae
> compression of submentovertical diameter
> elongation of occipitofrontal diameter
> There is associated marked bulging of the forehead due to caput formation.
what is the ocipitofrontal diameter?
- 11.5 cm
- form the occipital protuberance to the root of the nose.
- It is the engagement diameter in occipito-posterior position.
when does the baby go into cephalic presentation in normal pregnancy ?
32-36th week
