Malpresentations

Face Presentation

In face presentation (0.3% of presentations at or near term), the fetal neck is sharply extended so the occiput is in contact with the fetal back. The face is the presenting part. Diagnosis is made by palpation of the fetal face on vaginal exam.

Sinciput Presentation

The fetal head assumes a position between vertex presentation and face presentation so that the anterior fontanel presents first.

Brow Presentation

The fetal head assumes a position such that the eyebrows present first. This forces a large diameter through the pelvis; usually, vaginal delivery is possible only if the presentation is converted to a face or vertex presentation.

Breech Presentations

In breech presentations, the presenting fetal part is the buttocks. Normally, the delivery is C-section. Incidence: 3.5% at or near term but much greater in early pregnancy (14%). Those found in early pregnancy will often spontaneously convert to vertex as term approaches.

Risk Factors

■ Congenital anomalies such as hydrocephalus or anencephaly

■ Uterine anomalies

■ Multiple gestation

■ Placenta previa

Diagnosis can be made by:

■ Leopold maneuvers

■ Ultrasound

Types of Breech

■ Frank breech (65%): The thighs are flexed (bent forward) and the legs are extended (straight) over the anterior surfaces of the body (feet are in front of the head or face).

■ Complete breech (25%): The thighs are flexed (bent) on the abdomen and the legs are flexed (folded) as well.

■ Incomplete (footling) breech (10%): One or both of the hips are not flexed so that a foot lies below.

Management

■ Normally, C-section is the form of delivery.

■ External cephalic version: This is maneuvering the infant to a vertex position. Can be done only if breech is diagnosed before onset of labor and the GA > 37 weeks. The success rate is 75%, and the risks are pla-cental abruption or cord compression.

■ Trial of breech vaginal delivery: This is the attempt at a vaginal delivery. It can be done only in a frank breech, GA > 36 weeks, fetal weight 2,500 to 3,800 g, fetal head flexed, and favorable pelvis. Risks are greater for birth trauma (especially brachial plexus injuries) and prolapsed cord that entraps the aftercoming head.

Vaginal delivery is possible only if the fetus is mentum anterior; mentum posterior cannot deliver vaginally ^ cesarean section.

Sinciput and sinciput presentation are usually transient and almost always convert to vertex or face.

Why is pelvimetry and head position so important in frank breech vaginal delivery? Because the head doesn't have time to mold in order to fit through the birth canal.

Engagement indicates that the pelvic inlet of the maternal bony pelvis is sufficiently large to allow descent of the fetal head.

Engagement is measured by palpation of the presenting part of the occiput.

Descent occurs throughout the passage through the birth canal, as does flexion of the fetal head.

Shoulder Dystocia

Shoulder dystocia occurs when, after the fetal head has been delivered, the fetal shoulder is impacted behind the pubic symphysis.

Risk Factors

■ Macrosomia

■ Gestational diabetes

■ Maternal obesity

■ Post-term delivery

■ Prolonged stage 2 of labor

Complications

■ Fetal humeral/clavicular fracture

■ Brachial plexus nerve injuries

■ Hypoxia/death

Treatment

Several maneuvers can be done to displace the shoulder impaction:

■ Suprapubic pressure on maternal abdomen

■ McRoberts maneuver: Maternal thighs are sharply flexed against maternal abdomen. This decreases the angle between the sacrum and spine and may dislodge fetal shoulder.

■ Woods corkscrew maneuver: Pressure is applied against scapula of posterior shoulder to rotate the posterior shoulder and "unscrew" the anterior shoulder.

■ Posterior shoulder delivery: Hand is inserted into vagina and posterior arm is pulled across chest, delivering posterior shoulder and displacing anterior shoulder from behind pubic symphysis.

■ Break clavicle or cut through symphysis

■ Zavanelli maneuver: If the above measures do not work, the fetal head can be returned to the uterus. At this point, a C-section can be performed.

CARDINAL MOVEMENTS OF LABOR

The cardinal movements of labor are changes in the position of the fetal head during passage through the birth canal. The movements are as follows: engagement, flexion, descent, internal rotation, extension, and external rotation.

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