Occipito posterior position

Vaccume extraction

Review for conditions:

- vertex presentation;

- term fetus;

- cervix fully dilated;

- head at least at 0 station or no more than 2/5 above symphysis pubis.

Check all connections and test the vacuum on a gloved hand.

Provide emotional support and encouragement. If necessary, use a pudendal block.

Assess the position of the fetal head by feeling the sagittal suture line and the fontanelles.

Identify the posterior fontanelle (Fig P-7).

Apply the largest cup that will fit, with the center of the cup over the flexion point, 1 cm anterior to the posterior fontanelle. This placement will promote flexion, descent andautorotation with traction (Fig P-8).

An episiotomy may be needed for proper placement at this time. If an episiotomy is not necessary for placement, delay the episiotomy until the head stretches the perineum or the perineum interferes with the axis of traction. This will avoid unnecessary blood loss.

Check the application. Ensure there is no maternal soft tissue (cervix or vagina) within the rim

With the pump, create a vacuum of 0.2 kg/cm2 negative pressure and check the application.

Increase the vacuum to 0.8 kg/cm2 and check the application.

After maximum negative pressure, start traction in the line of the pelvic axis and perpendicular to the cup. If the fetal head is tilted to one side or not flexed well, traction should be directed in a line that will try to correct the tilt or deflexion of the head (i.e. to one side or the other, not necessarily in the midline).

With each contraction, apply traction in a line perpendicular to the plane of the cup rim (Fig P-9). Wearing high-level disinfected gloves, place a finger on the scalp next to the cup during traction to assess potential slippage and descent of the vertex.

Between contractions check:

- fetal heart rate;

- application of the cup.

TIPS

Never use the cup to actively rotate the babys head. Rotation of the babys head will occur with traction.

The first pulls help to find the proper direction for pulling.

Do not continue to pull between contractions and expulsive efforts.

With progress, and in the absence of fetal distress, continue the guiding pulls for a maximum of 30 minutes.

FAILURE

Vacuum extraction failed if:

- The head does not advance with each pull;

- The fetus is undelivered after three pulls with no descent, or after 30 minutes;

- The cup slips off the head twice at the proper direction of pull with a maximum negative pressure.

Every application should be considered a trial of vacuum extraction. Do not persist if there is no descent with every pull.

If vacuum extraction fails, use vacuum extraction in combination with symphysiotomy (see below) or perform caesarean section.

VACUUM EXTRACTION AND SYMPHYSIOTOMY

Vacuum extraction may be used in combination with symphysiotomy in the following circumstances:

- the head is at least at -2 station or no more than 3/5 palpable above the symphysis pubis;

- caesarean section is not feasible or immediately available;

- the provider is experienced and proficient in symphysiotomy;

- vacuum extraction alone has failed or is expected to fail;

there is no major degree of disproportion.

Contraindications to Vacuum Extraction

Vacuum operation is contraindicated in the following instances:

Operator inexperience

Inability to achieve acorrect application

An inadequate trial of labor

Lack of a standard indication

Uncertainty concerning fetal position and station

Suspicion of fetopelvic disproportion

Fetal malpositioning (eg, breech, face, brow)

Known or suspected fetal coagulation defects

Relative contraindications are as follows:

Prematurity (fetus 10 cm) is the smallest diameter of the pelvis.

Plane of the pelvic outlet: This consists of 2 triangular areas created from the connection of an imaginary line between the 2 ischial tuberosities. The apex of the posterior triangle is at the tip of the sacrum, and the apex of the anterior triangle is under the pubic arch. The following 3 diameters of the outlet are of importance:

Anteroposterior diameter: This is normally 9.5-11.5 cm and extends from the lower margin of the symphysis pubis to the tip of the sacrum.

Transverse diameter: This is commonly 11 cm and is the distance between the inner edges of the ischial tuberosities.

Posterior sagittal diameter: This usually exceeds 7 cm and extends from the tip of the sacrum to a right-angle intersection with the line between the ischial tuberosities.

Relevant terminology

Engagement: This occurs when the biparietal diameter in a vertex position passes through the plane of the pelvic inlet. Thus, the widest part of the fetal head has entered the true pelvis. Engagement is generally achieved when the leading bony point of the skull has reached the level of the ischial spines (0 station).

Presentation: This is the description of the presenting fetal part occupying the maternal pelvic inlet (eg, cephalic, breech, shoulder).

Lie: This term describes the relationship between the fetal longitudinal axis and the maternal longitudinal axis (eg, longitudinal, oblique, transverse).

Position: This term describes the relationship of the fetal presenting part to the maternal pelvis.

Asynclitism: This term describes the condition when the fetal head is turned in the maternal pelvis such that one parietal bone is closer to the pelvic outlet.

Determination of position

For cephalic presentations, the reference point is the occiput, whereas in breech presentations, the reference point is the sacrum.

Position is always described in reference to the maternal right or left side of the pelvis.

Determination of the position is crucial in forceps application and traction. The fontanels and sutures are used to determine the position. The finding that the fontanels are not easily palpable is not uncommon; this may occur because of distortion, molding, or caput formation.

The position can be determined by finding the location of the sagittal suture and its relationship to the posterior portion of the ear, if palpable. If the sagittal suture is in a U formation, an anterior asynclitism presentation should be suspected (ie, presentation of the anterior parietal bone of the fetal head). Conversely, if the sagittal suture is in the shape of an inverted U, this may indicate posterior asynclitism (ie, posterior parietal bone) presentation.

Most fetuses can be delivered by forceps if they are in or can be maneuvered (manually or by forceps) into an occiput anterior or posterior position.

Correct determination of the position may be the most important step prior to forceps application.

Contraindications

The following are contraindications to forceps-assisted vaginal deliveries:

Any contraindication to vaginal delivery (see Normal Labor and Delivery)

Refusal of the patient to verbally consent to the procedure

Cervix not fully dilated or retracted

Inability to determine the presentation and fetal head position

Inadequate pelvic size

Confirmed cephalopelvic disproportion

Unsuccessful trial of vacuum extraction (relative contraindication)

Absence of adequate anesthesia/analgesia

Inadequate facilities and support staff

Inexperienced operator