16. Cephalic presentation – brow , face and chin. Mechanism of delivery and management

Question 1

the fetal skull has how many different parts ?

Answer 1

cranium
face
base

Question 2

describe the base of the skull in a baby ?

Answer 2

base of the skull has large, ossified, firmly united, and noncompressible bones.
This serves to protect the vital structures contained within the brain stem.

Question 3

what are the specific bones in the cranium ?

Answer 3

the occipital bone posteriorly,

two parietal bones bilaterally,

two frontal

two temporal bone

Question 4

describe the cranial bones ?

Answer 4

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

Question 5

where does the sagittal suture lie ?

Answer 5

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.

Question 6

where does the lamboid suture lie ?

Answer 6

from the posterior fontanelle laterally and serves to separate the occipital from the parietal bones.

Question 7

where does the coronal suture lie ?

Answer 7

The coronal suture extends from the anterior fontanelle laterally and serves to
separate the parietal and frontal bones.

Question 8

where does the frontal suture lie

Answer 8

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

Question 9

what is the fontelle ?

Answer 9

the point where the sutures intersect are known as fontanelles, the most important of which are the anterior and posterior fontanelles

Question 10

when does the posterior fontanelle close ?

Answer 10

closes at 6 to 8 weeks after birth

Question 11

when does the anterior fontanelle close ?

Answer 11

anterior fontanelle does not become ossified until about 18 months

Question 12

why does the anterioir fontanelle close after such long time

Answer 12

allows the skull to accommodate the tremendous growth of the infant’s brain
after birth

Question 13

cephalic presentation can be classified into ?

Answer 13

vertex
face /chin
brow
oskie

Question 14

describe vertex presentation ?

Answer 14

the head is flexed and the occiput leads the way

Question 15

what are the subclassifications for vertex presentation ?

Answer 15

the vertex presentation is further classified into

right , left occipitoanterioir

right/ left occipital transverse

right /left/straight occipitoposterioir

Question 16

why is occiput anterior ideal ?

Answer 16

optimal for extension

Question 17

why is occipitoposterior not ideal ?

describe the mechanism of labour

Answer 17

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

Question 18

what predisposes face presentation ?

Answer 18

Multiparity with pendulous abdomen
Contracted pelvis
Flat pelvis
pelvic tumors

fetal
anencephaly
prematurity ,
macrosomia ,

Question 19

face presentations are classified according to the position of the ?

Answer 19

mentalis

Question 20

what are the sub classification of face presentation

Answer 20

left/right mento anterior
left/right mento posterior
left/right mento transverse

most common position is left mentoanterior

Question 21

which of the sub classification of face presentation cannot be delivered vaginally ? and why?

Answer 21

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

Question 22

what is brow presentation ?

Answer 22

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

Question 23

the submentobregmatic diameter is how long ?

Answer 23

9.5cm

junction of the neck and lower jaw to centre of anterior fontanelle

Question 24

submentobregmatic diameter is for which presentation ?

Answer 24

face presentation

Question 25

anteroposterior diametre when the head is flexed in vertex labour ?

Answer 25

suboccipitobregmatic -9.5cm

engagement diameter in occipito-anterior with complete flexion.

Question 26

what causes brow presentation ?

Answer 26

same as face presentation

especially in flat pelvis

Question 27

mechanism of labour in face presentation ?

Answer 27

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

Question 28

diagnosis of face presentation ?

Answer 28

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

Question 29

what is complications of face presentation

Answer 29

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

Question 30

diagnosis brow presentation :

Answer 30

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

Question 31

mechanism of brow delivery ?

Answer 31

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

Question 32

what is persistent ocipitoposterioir presentation?

Answer 32

malposition not malpresentation

Question 33

diagnosis of ocipitoposterioir

Answer 33

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.

Question 34

management of ocipitoposteroir

Answer 34

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

Question 35

causes of occipitoposterior presentation?

Answer 35

The shape of the pelvis: anthropoid and android pelvis

Maternal kyphosis

Question 36

describe management of face presentation ?

Answer 36

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

Question 37

what are the complications in brow presentation?

Answer 37

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.

Question 38

what is the ocipitofrontal diameter?

Answer 38

• 11.5 cm
  
  • form the occipital protuberance to the root of the nose.
  • It is the engagement diameter in occipito-posterior position.

Question 39

when does the baby go into cephalic presentation in normal pregnancy ?

Answer 39

32-36th week