ABNORMAL PRESENTATIONS: SINCIPUT, BROW, FACE - PowerPoint Presentation

Slide1

ABNORMAL PRESENTATIONS: SINCIPUT, BROW, FACE

Slide2

ORIENTATION IN UTERO

LIE=

orientation of the long axis of the fetus to the long axis of the uterus

Longitudinal orientation:

- fetus and the mother are in the same verical axis

- is the most common lie

Transverse orientation:

- fetus at right angles to mother

Oblique orientation:

- fetus at 45⁰ angle to mother

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1. Transverse fetal lie 2. Longitudinal fetal lie

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FETAL PRESENTATION

The presenting part is that portion of the fetal body that is either foremost within the birth canal or in closest proximity to it

- it can be felt through the cervix on vaginal examination;

In

logitudinal lies

, the presenting part is either the fetal head or breech, creating

cephalic

and

breech presentations

;

When the fetus lies with the long axis

transversely

, the

shoulder

is the presenting part and is felt through the cervix on vaginal examination;

In most normal pregnancies, the fetus settles into the mother’s pelvic cavity from week 36 onwards, ready for labour and birth.

About

8 in 10 fetuses settle head downwards, facing the mother’s back, with the chin resting on the chest. In this presentation, the fetus is in the optimum position for birth, and a normal vaginal delivery is usually possible

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Cephalic presentation Breech presentation Shoulder

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ATTITUDE

= degree of extension-flexion of the fetal head

Vertex: head is maximally flexed; is the most common attitude

Military (Sinciput): head is partially flexed

Brow: head is partially extended

Face: head is maximally extended

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ATTITUDE

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FETAL POSITION Position refers to the relationship of an chosen portion of the fetal presenting part to the right or left side of the maternal birth canal According with each presentation there may be two positions: Right or Left

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For still more acurate orientation the relationship of a given portion of the presenting part to the anterior, transverse or posterior portion of the maternal pelvis is considered Because the presenting part in right or left positions may be directed anteriorly (A), transversely (T) or posteriorly (P), there are six varieties of each of the presentation

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Positions in vertex presentation

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TYPES OF CEPHALIC PRESENTATIONS Such presentations are classified acording to the relationship between the head and body of the fetus Ordinarily, the head is flexed sharply so that the chin is in contact with the torax - the occipital fontanel is the presenting part - the presentation is referred to as a vertex or occiput presentation

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Much less commonly, the fetal neck may be sharply extended so that the occiput and back come in contact and the face is foremost in the birth canal Face presentation

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The fetal head may asume a position between these extremes: - partialy flexed in some cases, with the anterior (large) fontanel or bregma presentig to have a Sinciput presentation - or partially extended, in other cases, to have a Brow presentation Brow presentation Sinciput presentation

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The last two presentations (sinciput and brow) are usually transient As labor progresses, sinciput and brow presentations almost always are converted into vertex or face presentations by neck flexion or extension. Failure to do so can lead to dystocia a. Sinciput presentation b. Brow presentation c. Face presentation a. b. c.

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SINCIPUT PRESENTATION

DEFINITION:

-

A

lso

known as “military

position”

,

occurs when the head is neither flexed

nor

extended

. The anterior fontanel is felt as the presenting part

.

EPIDEMIOLOGY

:

-

Sinciput

presentation occurs in 1 of every

1000- 2000

live births

POSITION:

-

The

anterior fontanel (bregma)

is

the

point of designation and can

present

in any position relative to the maternal pelvis.

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DIAMETER: - presenting diameter is occipito-frontal (12,5 cm) ETIOLOGY:

MATERNAL FACTORS:

uterine malformationsabdominal tumors- cephalopelvic disproportion

OVULAR FACTORS:

Small head

Placenta praevia

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DIAGNOSIS:

-The

d

iagnosis

of a

sinciput

presentation

is

rare

made with abdominal palpation by Leopold maneuvers

- Vaginal examination in labour:

A

fter

the cervix has a 4-5 cm dilation at the sagittal suture's extremities, both fontanelles (anterior and posterior

) can be palpated;

In the cranial presentation only the little

fontanelle

is palpated

.

- Ultrasound evaluation reveals

the cephalic extremity in the intermediate

attitude

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DIFFERENTIAL DIAGNOSIS: 1. Vertex presentation 2. Brow presentation 3. Facial presentationMECHANISM OF LABOUR:The engagement is done with difficulty due to the large size of the fronto-occipital diameter (12,5 cm) for small fetuses or it is not done at all for large fetuses.

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When

the circumference gets on the pelvic-

perineal

floor, there are possible three situations

:

1.

there has to be made a moderate flexion of the cephalic extremity, followed by occiput rotation to

symphysis

;

the delivery will be done like in occipito-posterior presentation;

2.

the occiput rotates posteriorly with difficult engagement

;

3.

cephalic extremity remains in intermediate attitude, the rotations is not performed anymore and the birth mechanism cannot continue; the birth must be resolved by

obstretic

intervention

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MANAGEMENT :

If

there is any other relative indication for cesarean surgery,

the surgery

will be performed from the start

.

For all the other pregnant a birth prove will be

performed (2-4 hours);

if

the

engagement

was not produced

: cesarean

surgery

will be perform

Birth

evolution

prognosis is

reserved

Maternal prognosis is

reserved

from many reasons:

-

the long duration of a

birth

-

in 40-50% of cases it is required an

obst

etrical

or surgical

intervation

-

the hemorrhagic and infection risk is higher

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BROW PRESENTATION

DEFINITION:

-

In a brow presentation, the fetal head is midway between full flexion (vertex) and hyperextension (face) along a longitudinal axis. The presenting portion of the fetal head is between the orbital ridge and the anterior fontanel. The face and chin are not included.

EPIDEMIOLOGY:

-

Brow presentation is the least common of all fetal presentations and the incidence varies from 1 in 500 deliveries to 1 in 1400 deliveries

.

POSITION:

-

The frontal bones are the point of designation and can present (as with the occiput during a vertex delivery) in any position relative to the maternal pelvis

.

-

When the sagittal suture is transverse to the pelvic axis and the anterior fontanel is on the right maternal side, the fetus would be in the right

fronto

-

transverse

position (RFT

).

- Most frequent positions are: right fronto-posterior position and left fronto-anterior position

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DIAMETER: - presenting diameter is occipito-mental (13,5 cm)ETIOLOGY:

MATERNAL FACTORS

:- cephalopelvic disproportion or pelvic contracture- uterine malformations- uterin fibroma

OVULAR FACTORS:

- fetal malformations

- short neck

small

fetal thyroid

enlargement

musculoskeletal abnormality

placenta praevia

polyhydramnios

premature

rupture of

membranes (27%)

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DIAGNOSIS: - Diagnosis of a brow presentation can occasionally be made with abdominal palpation by Leopold maneuvers: a prominent occipital prominence is encountered along the fetal back, and the fetal chin is also palpable; however, the diagnosis of a brow presentation is usually confirmed by examination of a dilated cervix - Vaginal examination in labour: the orbital ridge, eyes, nose, forehead, and anterior fontanel are palpated the mouth and chin are not palpable, thus excluding face presentation - Fetal ultrasound evaluation again notes a hyperextended neck

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DIFFERENTIAL DIAGNOSIS: 1. Vertex presentation 2. Sinciput presentation 3. Facial presentationMECHANISM OF LABOUR: Three labor courses are possible when the fetal head engages in a brow presentation:The brow may convert to a vertex presentationThe brow may convert to a face presentationOr remain as a persistent brow presentation More than 50% of brow presentations will convert to vertex or face presentation and labor courses are managed accordingly when spontaneous conversion occurs.

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In

the brow presentation, the

occipito

-

mental

diameter, which is the largest diameter of the fetal head, is the presenting portion

.

Descent and internal rotation occur only with an adequate pelvis and if the face can fit under the pubic

arch

While the head descends, it becomes wedged into the hollow of the sacrum. Downward pressure from uterine contractions and maternal expulsive forces may cause the

mentum

to extend anteriorly and low to present at the perineum as a

mentum

anterior face presentation

.

If the

mentum

is anterior and the forces of labor are directed toward the fetal occiput, flexing the head and pivoting the face under the pubic arch, there is conversion to a vertex occiput posterior position. If the occiput lies against the sacrum and the forces of labor are directed against the fetal

mentum

, the neck may extend further, leading to a face presentation.

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Most

experts would agree that there is no mechanism of successful labor for a

termsized persistent

brow under most circumstances, and therefore vaginal delivery

is impossible.

However, vaginal delivery can occur if the

fetus

is quite

small

or if

the

pelvis

is very large

MANAGEMENT :

If dilatation and descent are progressing normally,

expectant

management

is

best

Forceps

deliveries

are

acceptable

if the brow converts to MA face or

vertex

Once progress in labor

has

ceased

, persistent brow presentations require a

cesarean delivery

, and all

operative

vaginal

maneuvers are

contraindicated

Birth evolution prognosis is

reserved

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FACE PRESENTATION

DEFINITION:

-

In

a face presentation, the fetal head and neck are hyperextended, causing the occiput to come in contact with the upper back of the fetus while lying in a longitudinal axis. The presenting portion of the fetus is the fetal face between the orbital ridges and the

chin

EPIDEMIOLOGY:

-

Face presentation occurs in 1 of every 600-800 live births, averaging about 0.2% of live

births

POSITION:

-

The fetal chin (

mentum

) is the point designated for reference during an internal examination through the cervix. The occiput of a vertex is usually hard and has a smooth contour, while the face and brow tend to be more irregular and soft.

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- Like the occiput, the mentum can present in any position relative to the maternal pelvis. For example, if the mentum presents in the left anterior quadrant of the maternal pelvis, it is designated as left mentum anterior (LMA).

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Positions in face presentation

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DIAMETER: - presenting diameter is submento- bregmatic (9.5 cm)ETIOLOGY:

MATERNAL FACTORS

:- grand multiparitymultiple gestationscephalopelvic disproportionuterine malformationsabdominal tumorsuterine fibroma

OVULATORY FACTORS

:

Prematurity

fetal

anomalies (hydrocephalus, anencephaly

)

neck

masses

large

infants

musculoskeletal

abnormality

several coils of ombilical cord around the neck

placenta praevia

polyhydramnios

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DIAGNOSIS:

-

Face presentation is diagnosed late in the first or second stage of labor by examination of a dilated

cervix

-

On digital examination, the distinctive facial features of the nose, mouth, and chin, the malar bones, and particularly the orbital ridges can be palpated

.

This

presentation can be confused with a breech presentation because the mouth may be confused with the anus and the malar bones or orbital ridges may be confused with the

ischial

tuberosities

The facial presentation has a triangular configuration of the mouth to the orbital ridges compared to the breech presentation of the anus and fetal genitalia

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1. Complete breech presentation 2. Face presentation - During Leopold maneuvers, diagnosis is very unlikely Diagnosis can be confirmed by ultrasound evaluation, which reveals a hyperextended fetal neck.

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DIFFERENTIAL DIAGNOSIS: 1. Vertex presentation 2. Sinciput presentation 3. Brow presentation 4. Breech presentationMECHANISM OF LABOUR: - While descending into the pelvis, the natural contractile forces combined with the maternal pelvic architecture allow the fetal head to either flex or extend - Following engagement in the face presentation, descent is made. The widest diameter of the fetal head negotiating the pelvis is the trachelobregmatic or submentobregmatic diameter, which is 10.2 cm (0.7 cm larger than the suboccipitobregmatic diameter).

Slide34

- i

nternal

rotation occurs between the

ischial

spines and the

ischial

tuberosities

, making the chin the presenting part, lower than in the vertex

presentation

-

Following internal rotation, the

mentum

is below the maternal

symphysis

, and delivery occurs by flexion of the fetal neck. As the face descends onto the perineum, the anterior fetal chin passes under the

symphysis

and flexion of the head occurs, making delivery possible with maternal expulsive

forces

The above mechanisms of labor in the term infant can occur only if the

mentum

is anterior and at term, only the

mentum

anterior face presentation is likely to deliver

vaginally

I

f

the

mentum

is posterior or transverse, the fetal neck is too short to span the length of the maternal sacrum and is already at the point of maximal extension. The head cannot deliver as it cannot extend any further through the

symphysis

and cesarean delivery is the safest route of delivery.

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-

Fortunately, the

mentum

is anterior in over 60% of cases of face presentation, transverse in 10-12% of cases, and posterior only 20-25% of the

time

-

Fetuses with the

mentum

transverse position usually rotate to the

mentum

anterior position, and 25-33% of fetuses with

mentum

posterior position rotate to a

mentum

anterior

position

-

When the

mentum

is posterior, the neck, head and shoulders must enter the pelvis simultaneously, resulting in a diameter too large for the maternal pelvis to accommodate unless in the very preterm or small

infant

-

Duration of labor with a face presentation is generally the same as duration of labor with a vertex presentation, although a prolonged labor may occur. As long as maternal or fetal compromise is not evident, labor with a face presentation may continue.

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MANAGEMENT : The average reported incidence of spontaneous or elective low forceps delivery in face presentation is 72% (range, 40% to 90%). The average rate of cesarean delivery is 15% and in only two series was it >29%In older series, up to 12% of face presentations were delivered by various operative vaginal procedures, including midforceps rotation, version and extraction, and manual conversion of face to vertex (Thorn maneuver) These procedures are associated with high perinatal mortality and maternal morbidity, and there is no place for them in the modern management of face presentation. Face presentation alone is not a contraindication to oxytocin stimulation of labor, and it can be done for the same reasons and with the same precautions as in vertex presentation

Slide37

F

orceps

delivery in MA presentation can be

accomplished

by

using the same criteria that would be used in vertex presentation, but

midforceps

delivery

in face presentation should be

abandoned

For obvious

reasons,

application

of the vacuum extractor is contraindicated with face

presentation

In

any face presentation, as in

vertex

presentation

, if progress in dilatation and descent ceases despite

adequate

contractions

, delivery should be accomplished by cesarean

section

The only series using fetal monitoring extensively in the management of

face

presentation

reported variable decelerations in 59% of 29 infants, severe variables

in

29

%, and late decelerations in 24%.

Slide38

It seems plausible that the increased incidence of

fetal

heart

rate abnormalities is due in part to abnormal pressure on the extended

head,

neck

, or eyes, similar to the mechanism of heart rate abnormalities described

in

occiput

posterior

presentations

Therefore, face presentation is an indication

for

electronic

fetal monitoring. To avoid damaging the fetal eyes or scarring the face

with

an

electrode, external monitoring should be

used

Birth evolution prognosis is

reserved