Obstetrics 13: Assisted Delivery Portal
Introduction
Assisted vaginal delivery is an important skill for managing
the second stage of labor. Although the intent of most practitioners in
smaller hospitals is to deliver infants of low-risk mothers,
occasionally one encounters situations necessitating urgent delivery of
an infant. The knowledge and skill necessary to effect this outcome
vaginally can be useful—if not lifesaving—for the infant and mother.
Consider Assisted Vaginal Delivery for These Indications:
Maternal
- Need to avoid voluntary expulsive effort (cardiac or cerebrovascular disease)
- Maternal exhaustion
- Analgesia interfering with woman's voluntary expulsive effort
- Marked resistance of the perineum and vaginal musculature with prolonged second stage or failed progress in the second stage of labor
- The following intervals for the second stage of labor—when
exceeded—should cause the practitioner to assess again the risk versus
benefit of allowing labor to continue.
- Primigravida: More than 3 hours with regional anesthetic or more than 2 hours without a regional anesthetic
- Multigravida: More than 2 hours with a regional anesthetic or more than 1 hour without a regional anesthetic
When progression of the second stage of labor is slow, be sure to document decisions in the medical record and maintain continuous fetal heart monitoring.
Fetal
- Abnormalities in FHR patterns
- Premature separation of the placenta with hemorrhage
- Problems in cephalopelvic relations (as in failure to rotate or persistent occiput posterior or transverse positions)
- Mild degrees of deflexion or asynclitism (malalignment of the presentation of the head in the pelvis)
Prerequisites for Assisted Vaginal Delivery
- The membranes must be ruptured.
- The cervix must be completely dilated.
- The fetus should be full term.
- The fetus must be in the vertex position verified by a bimanual exam.
- The position of the head (fetal skull, not caput) must be known and be deeply engaged (lower than Station 0—the plane of the pelvic inlet or at level of ischial spines).
- The delivering physician must be familiar with the instruments being used.
- Assess the maternal-fetal size relationship: there should be no known cephalopelvic disproportion.
- Give adequate anesthesia.
- Abandon the procedure if it does not progress easily.
- Prepare a plan in case of failure of the assisted delivery, particularly if fetal status deteriorates.
Use of the Vacuum Extractor
Advantages:
- Some studies support the safety of vacuum extraction over forceps deliveries.
- Plastic cup extractors are excellent for low and outlet OA and OP positions.
- The vacuum extractor is simpler to apply than forceps with fewer mistakes in applications.
- Teaches one the pelvic curve very well (self directing) and allows autorotation.
- Less force is applied to the fetal head.
- The procedure requires less anesthesia (local often suffices) and results in fewer vaginal and cervical lacerations.
Disadvantages:
- Traction may be applied only during contractions.
- Proper traction is necessary to avoid losing suction, which may be an advantage.
- Delivery may take longer than with forceps (impractical when rapid delivery is necessary for fetal distress).
- There is a small increase in the incidence of cephalhematomas.
- If molding is present, suction is difficult to maintain.
Contraindications:
- Prematurity (< 37 weeks gestation)
- Breech, face, brow, or transverse presentation
- Incomplete cervical dilatation
- Cephalopelvic disproportion
- Head not engaged
Indications for Discontinuance:
- Failure to achieve extraction after 10 minutes at maximal pressure
- Failure to achieve extraction within 30 minutes of initiation of procedure
- Disengagement of extractor cup 3 times
- No significant progress in 3 consecutive pulls
- Fetal scalp trauma inflicted by extractor cup
Procedure: The acronym for doing assisted deliveries follows:
A — |
Anesthesia adequate? Local and/or pudendal blocks are usually adequate. |
B — |
Bladder empty? Catheterize if needed. |
C — |
Cervix completely dilated? |
D — |
Determine position of the fetal head? Think Dystocia. |
E — |
Equipment ready for episiotomy and delivery? |
F — |
Fontanel identified ? |
| The vertex is wiped clean of blood and fluid. The labia are spread, and the cup is compressed and inserted. | |
F — |
The cup is inserted and positioned to promote flexion when the operator applies traction. The vacuum should be placed about 3 cm in front of the posterior fontanelle. Sweep a finger around the cup to ensure no maternal tissue is trapped beneath the cup. The cup can be rotated several times to ensure that no maternal soft tissue has been caught. Negative pressure is then raised to 100 mm Hg, and the cup is reexamined for position and maternal tissue. With the next contraction, the negative pressure is rapidly raised to 380 to 580 mm Hg, not exceeding 600 mm Hg. (For Mityvac, pressures are 10 and 50, respectively.) |
G — |
Gentle traction in the direction of the pelvic axis. If the shaft is bent or a rotary force is applied or if the traction is too oblique or in the wrong direction, the vacuum seal will likely be broken. A hissing sound will be heard, or air bubbles will form under the cup on the side of the seal break. Apply traction only during contractions. |
H — |
Halt traction when the contraction is over; reduce the pressure to 100 mm Hg by triggering the vacuum release valve. Repeat the cycle when the next contraction begins. Halt the procedure if you have had disengagement of the cup 3 times, have had no progress in 3 consecutive pulls, or have been attempting delivery for 30 minutes. (Remember the number 3). |
I — |
Make Incision for the episiotomy when head is being delivered. This is not done by all physicians. |
J — |
Remove vacuum cup when Jaw is delivered. |
Post Delivery Care
The same situation applies following vacuum extraction deliveries as
forceps deliveries, specifically looking for evidence of birth trauma
to mother and infant. Localized caput formation lasts from 10 minutes
to 1 week, usually disappearing within 24 to 48 hours after delivery.
There is a slightly higher incidence of hyperbilirubinemia in the
infant after vacuum extraction.
Precautions with Assisted Deliveries
Use caution in attempting forceps after the vacuum extractor has
failed. (Use only if the head is right on the perineum.)
Use of Forceps
Note: Forceps delivery should only be attempted by those trained in their use.
Description of Forceps: Simpson forceps are commonly used, and because of the fenestrated blade, apply more traction to the fetal head. However, there is then greater risk of fetal lacerations and bruising. Simpson forceps consist of 2 interlocking parts: left and right blades, which are named according to the relationship to the maternal pelvis. The distal end of the blade is called the toe and the part nearest the shank is the heel. The blades are curved on the inner-medial side (producing the cephalic curve conforming to the fetal head) and on the upper-superior edge (producing the pelvic curve conforming to the maternal pelvis). The 2 blades fit together by an articulating lock located on the shank.
Procedure: The acronym for doing assisted deliveries is the same as described for the vacuum extractor.
A—Anesthesia
adequate? Local and/or pudendal blocks are usually adequate.
B—Bladder
empty? Catheterize if needed.
C—Cervix
completely dilated?
D—Determine
position of the fetal head? Think Dystocia.
E—Equipment
ready for episiotomy and delivery?
F—Fontanel
identified ?
Some physicians coat the blades with lubricant for ease of application. The left forcep handle is held in the left hand first during insertion with a pencil grip with the cephalic curve inward toward the vulva and the shank perpendicular to the floor. The blade is applied to the left side of the fetal head (in OA position) normally with the right hand protecting the maternal left pelvis and guiding the blade into position. The thumb is placed on the heel; this is the inserting force, not the handle. The right forcep handle is then held in the right hand during insertion and is applied to the right side of the fetal head on the mother's right with the left hand protecting the maternal right pelvis and guiding the blade into position. The handles should fit together if the blades are correctly applied. The posterior fontanelle should be midway between the shanks and 1 cm anterior to the plane of the shanks. This ensures the proper flexion of the head to present the narrowest diameter to the pelvis. If the posterior fontanelle is higher than 1 cm, then traction will cause extension of the head. The fenestration should be just barely palpable. You should not be able to insert more than a fingertip. If you are able, then the blades aren't inserted enough to be below the malar eminence. The sagittal suture should be in the middle, midway between the shanks. In summary, to make sure the forceps are applied correctly, check Position for Safety—Posterior fontanelle, Fenestration, Sagittal.
G—Gentle traction (Pajot's maneuver). Traction is made with gentle pull gradually increasing and decreasing to mimic the uterine contraction (unless an emergency).
H—Handle for the episiotomy when perineum distends (if necessary).
I—Make Incision for the episiotomy when perineum distends (if necessary).
J—Remove forceps when Jaw is reachable.
Post Delivery Care
After assisted delivery, a thorough cervical, vaginal, and
rectal exam for buttonhole tears is essential to rule out lacerations.
Be ready for postpartum hemorrhage. Look for evidence of birth trauma
to mother and infant (fractured clavicle, cephalhematoma,
lacerations-abrasions, facial nerve palsy, etc.).
The first postpartum day, discuss the mother’s perceptions with her about the delivery.