ABNORMAL PRESENTATIONS: SINCIPUT, BROW,

FACE

*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

1. Transverse fetal lie

2. Longitudinal fetal lie

*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

Cephalic presentation Breech presentation Shoulder

* 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

*ATTITUDE

*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

• 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

*Positions in vertex presentation

*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

• 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

• 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

• 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.

SINCIPUT PRESENTATIONDEFINITION:

- Also 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.

DIAMETER:

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

ETIOLOGY:

MATERNAL FACTORS:- uterine

malformations- abdominal

tumors- cephalopelvic

disproportion

OVULAR FACTORS:

- Small head

- Placenta praevia

DIAGNOSIS:

-The diagnosis of a sinciput presentation is rare made with abdominal palpation by Leopold maneuvers

- Vaginal examination in labour:

• After 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

DIFFERENTIAL DIAGNOSIS:

1. Vertex presentation

2. Brow presentation

3. Facial presentation

MECHANISM 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.

• 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

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 obstetrical or surgical intervation

- the hemorrhagic and infection risk is higher

BROW PRESENTATIONDEFINITION:

- 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

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%)

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

DIFFERENTIAL DIAGNOSIS:

1. Vertex presentation

2. Sinciput presentation

3. Facial presentation

MECHANISM OF LABOUR:

Three labor courses are possible when the fetal head engages in a brow presentation:

I. The brow may convert to a vertex presentation

II. The brow may convert to a face presentation

III. Or 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.

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.

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

FACE PRESENTATIONDEFINITION:

- 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.

- 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).

Positions in face presentation

DIAMETER:

- presenting diameter is submento- bregmatic (9.5 cm)

ETIOLOGY:

MATERNAL FACTORS:

- grand multiparity- multiple

gestations- cephalopelvic

disproportion- uterine

malformations- abdominal

tumors- uterine 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

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

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.

DIFFERENTIAL DIAGNOSIS:

1. Vertex presentation

2. Sinciput presentation

3. Brow presentation

4. Breech presentation

MECHANISM 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).

- internal 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

* If 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.

- 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.

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

• Forceps 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%.

• 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