CHAPTER 29: Operative Vaginal Delivery

Operative deliveries are vaginal deliveries accomplished with the use of forceps or a vacuum device. Once either is applied to the fetal head, outward traction generates forces that augment maternal pushing to deliver the fetus vaginally. The most important function of both devices is traction. In addition, forceps may also be used for rotation, particularly from occiput transverse and posterior positions.

According to the birth certificate data from the National Vital Statistics Report, forceps- or vacuum-assisted vaginal delivery was used for 3.2 percent of births in the United States in 2014. This is a decline from 9.0 percent in 1990 (Hamilton, 2015). For these deliveries, a vacuum is disproportionately selected, and the vacuum-to-forceps delivery ratio is nearly 5:1 (Merriam, 2017). In general, most of these attempts are successful. In 2006, only 0.4 percent of forceps trials in the United States and 0.8 percent of vacuum extraction attempts failed to result in vaginal delivery (Osterman, 2009).

If it is technically feasible and can be safely accomplished, termination of second-stage labor by traction instruments is indicated in any condition threatening the mother or fetus that is likely to be relieved by delivery. Some fetal indications include nonreassuring fetal heart rate pattern and premature placental separation (Schuit, 2012). In the past, forceps delivery was believed to be somewhat protective of the fragile preterm infant head. However, outcomes for neonates who weigh 500 to 1500 g do not significantly differ if delivered spontaneously or by outlet forceps (Fairweather, 1981; Schwartz, 1983).

Some maternal indications include heart disease, pulmonary compromise, intrapartum infection, and certain neurological conditions. The most common are exhaustion and prolonged second-stage labor. However, a specific maximum length beyond which all women should be considered for operative vaginal delivery has not been identified (American College of Obstetricians and Gynecologists, 2016).

Operative delivery is generally performed from either a low or outlet station. Additionally, forceps or vacuum delivery should not be used electively until the criteria for an outlet delivery have been met. In these circumstances, operative delivery is a simple and safe operation, although with some risk of maternal lower reproductive tract injury (Yancey, 1999).

Classification for operative vaginal delivery is summarized in Table 29-1. It emphasizes that the two most important discriminators of risk for both mother and neonate are station and rotation. Station is measured in centimeters, –5 to 0 to +5. Zero station reflects a line drawn between the ischial spines. Deliveries are categorized as outlet, low, and midpelvic procedures. High forceps, in which instruments are applied above 0 station, have no place in contemporary obstetrics.

Once station and rotation are assessed, several prerequisites are met and are listed in Table 29-1. For vacuum extraction, fetuses should also be at least 34 weeks’ gestation, and although infrequently used in the United States, fetal scalp blood sampling should not have been recently performed. Of requisites, ascertaining correct head position is essential, and the anatomy of the fetal skull is described in Figure 29-1. In unclear cases, sonography is useful to identify fetal orbits and nasal bridge to aid orientation (Malvasi, 2014).

Regional analgesia or general anesthesia is preferable for low forceps or midpelvic procedures, although pudendal blockade may prove adequate for outlet forceps. As discussed in Chapter 25 (Effects on Labor), regional analgesia during labor does not appear to increase the risk for operative delivery (Halpern, 2004; Marucci, 2007; Wassen, 2014).

The bladder is emptied to provide additional pelvic space and minimize bladder trauma. Urinary retention and bladder dysfunction are often short-term effects of forceps and vacuum deliveries (Mulder, 2012; Pifarotti, 2014). Notably, episiotomy and epidural analgesia, both common associates, are also identified risks for urinary retention. Symptoms are brief and typically resolve with 24 to 48 hours of passive Foley catheter bladder drainage.

There is an increased risk of certain morbidities for both mother and fetus when operative delivery is employed. In general, these are related to the ease with which the delivery is accomplished.

Maternal Morbidity

In general, a higher station and/or greater degrees of rotation increase the chance of maternal or fetal injury. Morbidity is most properly compared with morbidity from cesarean delivery, and not with that from spontaneous vaginal delivery. This is the most appropriate comparator because the alternative to indicated operative delivery is cesarean delivery. For example, postpartum wound or uterine infection is more frequent in women following cesarean compared with operative vaginal delivery (Bailit, 2016; Halscott, 2015). Moreover, in a study of more than 1 million births, Spiliopoulos and associates (2011) reported cesarean delivery, but not operative vaginal delivery, as a risk for peripartum hysterectomy.

Lacerations

The very conditions that lead to indications for operative delivery also increase the need for episiotomy and the likelihood of lacerations (de Leeuw, 2008). That said, forceps and vacuum deliveries are associated with higher rates of third- and fourth-degree lacerations as well as vaginal wall and cervical lacerations (Gurol-Urganci, 2013; Hirayama, 2012; Landy, 2011; Pergialiotis, 2014). These appear to occur more frequently with forceps compared with vacuum extraction, and especially if there is a midline episiotomy (Kudish, 2006; O’Mahony, 2010). Hagadorn-Freathy and coworkers (1991) reported a 13-percent rate of third- and fourth-degree episiotomy extensions and vaginal lacerations for outlet forceps, 22 percent for low forceps with less than 45-degree rotation, 44 percent for low forceps with more than 45-degree rotation, and 37 percent for midforceps deliveries.

In an effort to lower rates of third- and fourth-degree lacerations, and coincident with overall efforts to reduce routine episiotomy use, many advocate only indicated episiotomy with operative delivery. If episiotomy is required, a protective effect against these more extensive perineal lacerations may be afforded by mediolateral episiotomy (de Leeuw, 2008; de Vogel, 2012; Hirsch, 2008). Early disarticulation of forceps and cessation of maternal pushing during disarticulation can also be protective. Last, these injuries are more common with an occiput posterior position (Damron, 2004). Thus, manual or forceps rotation to an occiput anterior position and then subsequent traction delivery may decrease rates of lower reproductive tract injury (Bradley, 2013).

Pelvic Floor Disorders

This term encompasses urinary incontinence, anal incontinence, and pelvic organ prolapse. Operative vaginal delivery has been suggested as a possible risk for each of these. Proposed mechanisms include structural compromise and/or pelvic floor denervation secondary to forces exerted during delivery.

Parity and specifically vaginal delivery are risk factors for urinary incontinence (Gyhagen, 2013; Rortveit, 2003). But, many studies do not support an increased risk compared with vaginal delivery alone (Gartland, 2016; Leijonhufvud, 2011; MacArthur, 2016; Tähtinen, 2016).

Evidence linking anal incontinence with operative vaginal delivery is conflicting. Some studies show that anal sphincter disruption caused by higher-order episiotomy, but not delivery mode, is the main etiological factor strongly associated with anal incontinence (Bols, 2010; Evers, 2012; Nygaard, 1997). In contrast, others directly link operative delivery with this complication (Dolan, 2010; MacArthur, 2013). But, these studies may not be incongruous—recall that operative delivery is associated with increased rates of higher-order episiotomy. Importantly, several studies and reviews have not found cesarean delivery to be protective for anal incontinence (Nelson, 2010). Last, evidence linking pelvic organ prolapse with operative delivery also indicates mixed results (Gyhagen, 2013; Handa, 2012; Volløyhaug, 2015).

Perinatal Morbidity

Acute Perinatal Injury

These injuries are more frequent with operative vaginal delivery than with cesarean delivery or spontaneous vaginal delivery. Injuries may be seen with either method. They are more common with vacuum extraction, and types associated with this device include cephalohematoma, subgaleal hemorrhage, retinal hemorrhage, neonatal jaundice secondary to these hemorrhages, shoulder dystocia, clavicular fracture, and scalp lacerations. Cephalohematoma and subgaleal hemorrhage are both extracranial lesions described in Chapter 33 (Intracranial Hemorrhage). Forceps-assisted vaginal delivery has higher rates of facial nerve injury, brachial plexus injury, depressed skull fracture, and corneal abrasion (American College of Obstetricians and Gynecologists, 2015; Demissie, 2004; Dupuis, 2005). For intracranial hemorrhage, some studies have associated vacuum extraction with higher rates, whereas others show similar rates with either of the two methods (Towner, 1999; Wen, 2001; Werner, 2011).

Comparing operative vaginal with cesarean delivery, rates of extracranial hematoma, skull fracture, facial nerve or brachial plexus injury, retinal hemorrhage, and facial or scalp laceration are lower with cesarean delivery, and shoulder dystocia is eliminated. Importantly, however, fetal acidemia rates are not increased with operative delivery (Contag, 2010; Walsh, 2013). Intracranial hemorrhage rates are similar among newborns delivered by vacuum extraction, forceps, or cesarean delivery during labor (Towner, 1999). But, these rates are higher than among those delivered spontaneously or by cesarean delivery before labor. These authors suggest that the common risk factor for intracranial hemorrhage is abnormal labor. Werner and associates (2011), in their evaluation of more than 150,000 singleton deliveries, reported that forceps-assisted delivery was associated with fewer total neurological complications compared with vacuum-assisted or cesarean delivery. However, as a subset, subdural hemorrhage was significantly more frequent in both instrumental cohorts compared with neonates in the cesarean delivery group.

Comparing rotational operative delivery and second-stage cesarean delivery, maternal and neonatal morbidity rates are similar (Aiken, 2015; Bahl, 2013; Stock, 2013). For example, in their large series, Tempest and associates (2013) found similar morbidity rates among malpositioned fetuses during second-stage labor that underwent Kielland rotation, rotational vacuum extraction, or emergency cesarean delivery.

Comparing midforceps and cesarean delivery, reports of neonatal morbidity rates are from older studies and are conflicting. In the study by Towner and colleagues (1999), similar risks were reported for intracranial hemorrhage. Bashore and associates (1990) observed comparable Apgar scores, cord blood acid-base values, neonatal intensive care unit admission, and birth trauma between these two. In another study, however, Robertson and coworkers (1990) reported significantly higher rates of these adverse outcomes in the midforceps group. Hagadorn-Freathy and colleagues (1991) reported an increased risk for facial nerve palsy—9 percent—with midforceps delivery. In a recent report comparing low and midforceps procedures, Ducarme and coworkers (2015) found comparable morbidity rates.

Mechanisms of Acute Injury

The types of fetal injury with operative delivery can usually be explained by the forces exerted. In cases of cephalohematoma or subgaleal hemorrhage, suction and perhaps rotation during vacuum extraction may lead to a primary vessel laceration. Intracranial hemorrhage may result from skull fracture and vessel laceration or from vessel laceration alone due to exerted forces. With facial nerve palsy, one of the forceps blades may compress the nerve against the facial bones. The higher rates of shoulder dystocia seen with vacuum extraction may result from the angle of traction. With the vacuum, this angle creates vector forces that actually pull the anterior shoulder into the symphysis pubis (Caughey, 2005). To explain brachial plexus injury, Towner and Ciotti (2007) proposed that as the fetal head descends down the birth canal, the shoulders may stay above the pelvic inlet. Thus, similar to shoulder dystocia at the symphysis, this “shoulder dystocia at the pelvic inlet” is overcome by traction forces but with concomitant stretch on the brachial plexus.

Long-Term Infant Morbidity

Evidence regarding long-term neurodevelopmental outcomes in children born by operative delivery is reassuring. In an older study, Seidman and colleagues (1991) evaluated more than 52,000 Israeli Defense Forces draftees at age 17 years and found that regardless of delivery mode, rates of physical or cognitive impairments were similar. Wesley and associates (1992) noted similar intelligence scores among 5-year-olds following spontaneous, forceps, or vacuum deliveries. Murphy and coworkers (2004) found no association between forceps delivery and epilepsy in a cohort of more than 21,000 adults. In their epidemiological review, O’Callaghan and colleagues (2011) found no association between cerebral palsy and operative delivery. Last, Bahl and associates (2007) noted that the incidence of neurodevelopmental morbidity was similar in those undergoing successful forceps delivery, failed forceps with cesarean delivery, or cesarean delivery without forceps.

Data regarding midforceps deliveries are for the most part reassuring. Broman and coworkers (1975) reported that infants delivered by midforceps had slightly higher intelligence scores at age 4 years compared with those of children delivered spontaneously. Using the same database, however, Friedman and associates (1977, 1984) analyzed intelligence scores at or after age 7 years. They concluded that children delivered by midforceps had lower mean intelligence quotients compared with those delivered by outlet forceps. In yet another report from this database, Dierker and colleagues (1986) compared long-term outcomes of children delivered by midforceps with those delivered by cesarean after dystocia. The strength of this study is the appropriateness of the control group. These investigators reported that delivery by midforceps was not associated with neurodevelopmental disability. Last, Nilsen (1984) evaluated 18-year-old men and found that those delivered by Kielland forceps had higher intelligence scores than those delivered spontaneously, by vacuum extraction, or by cesarean.

If an attempt to perform an operative delivery is expected to be difficult, then it should be considered a trial. Moving the woman to an operating room for this attempt, which could be followed by immediate cesarean delivery if operative delivery fails, has merit. If forceps cannot be satisfactorily applied, then the procedure is stopped and either vacuum extraction or cesarean delivery is performed. With the former, if the fetus does not descend with traction, the trial should be abandoned and cesarean delivery performed.

With such caveats, cesarean delivery after an attempt at operative vaginal delivery was not associated with adverse neonatal outcomes if there was a reassuring fetal heart rate tracing (Alexander, 2009). A similar study evaluated 122 women who had a trial of midcavity forceps or vacuum extraction in a setting with full preparations for cesarean delivery (Lowe, 1987). Investigators found no significant difference in immediate neonatal or maternal morbidity compared with that of 42 women delivered for similar indications by cesarean but without such a trial. Conversely, in 61 women who had “unexpected” vacuum or forceps failure in which there was no prior preparation for immediate cesarean delivery, neonatal morbidity was higher.

Some factors associated with operative delivery failure are persistent occiput posterior position and birthweight >4000 g (Ben-Haroush, 2007; Verhoeven, 2016). However, Palatnik and associates (2016) found that risk factors poorly predicted success. In general, to avert morbidity with failed forceps or vacuum delivery, the American College of Obstetricians and Gynecologists (2015) cautions that these trials should be attempted only if the clinical assessment suggests a successful outcome. We also emphasize proper training.

Sequential instrumentation most often involves an attempt at vacuum extraction followed by one with forceps. This most likely stems from the higher completion rate with forceps compared with vacuum extraction noted earlier. This practice significantly increases risks for fetal trauma (Dupuis, 2005; Gardella, 2001; Murphy, 2011). Because of these adverse outcomes, the American College of Obstetricians and Gynecologists (2015) recommends against the sequential use of instruments unless there is a “compelling and justifiable reason.”

As the rate of operative vaginal delivery has declined, so have opportunities for training (Fitzwater, 2015; Kyser, 2014). In many programs, training in even low and outlet forceps procedures has reached critically low levels. For residents completing training in 2015, the Accreditation Council for Graduate Medical Education reported a median of only five forceps deliveries, and that for vacuum deliveries was 16.

Because traditional hands-on training has evolved, residency programs should have readily available skilled operators to teach these procedures by simulation as well as through actual cases (Skinner, 2017; Spong, 2012). And, the effectiveness of simulation training has been reported (Dupuis, 2006, 2009; Leslie, 2005). In one program, maternal and neonatal morbidity rates with operative delivery decreased after the implementation of a formal education program that included a manikin and pelvic model (Cheong, 2004). In another, a 59-percent increase in forceps deliveries over 2 years was related to a single experienced and proactive instructor assigned to teach forceps to residents in labor and delivery (Solt, 2011).

Design

Forceps refers to the paired instrument, and each member of this pair is called a branch. Branches are designated left or right according to the side of the maternal pelvis to which they are applied (Fig. 29-2). Each branch has four components: blade, shank, lock, and handle (Fig. 29-3). Each blade has a toe, a heel, and two curves. Of these, the outward cephalic curve conforms to the round fetal head, whereas the upward pelvic curve corresponds more or less to the curve of the birth canal. Some blades have an opening within or a depression along the blade surface and are termed fenestrated or pseudofenestrated, respectively. True fenestration reduces the degree of head slippage during forceps rotation. Disadvantageously, it can increase friction between the blade and vaginal wall. With pseudofenestration, the forceps blade is smooth on the outer maternal side but indented on the inner fetal surface. The goal is to reduce head slipping yet improve the ease and safety of application and removal of forceps compared with pure fenestrated blades. In general, fenestrated blades are used for a fetus with a molded head or for rotation. In most situations, however, despite these subtle differences any are appropriate.

The blades are connected to shanks, which may be parallel or overlapping. Locks are found on all forceps and help to connect the right and left branches and stabilize the instrument. They can be located at the end of the shank nearest to the handles (English lock), at the ends of the handles (pivot lock), or along the shank (sliding lock). Although varied in design, handles, when squeezed, raise compression forces against the fetal head. Thus, forces to consider include traction and compression.

Blade Application and Delivery

Forceps blades grasp the head and are applied according to fetal head position. If the head is in an occiput anterior (OA) position, two or more fingers of the right hand are introduced inside the left posterior portion of the vulva and then into the vagina beside the fetal head. The handle of the left branch is grasped between the thumb and two fingers of the left hand (Fig. 29-4). The blade tip is then gently passed into the vagina between the fetal head and the palmar surface of the fingers of the right hand (Fig. 29-5). For application of the right blade, two or more fingers of the left hand are introduced into the right posterior portion of the vagina to serve as a guide for the right blade. This blade is held in the right hand and introduced into the vagina. With each blade, the thumb is positioned behind the heel, and most of the insertion force comes from this thumb (Fig. 29-6). If the head is positioned in a left OA (LOA) or right OA (ROA) position, then the lower of the two blades is typically placed first. After positioning, the branches are articulated.

The blades are constructed so that their cephalic curve is closely adapted to the sides of the fetal head (Fig. 29-7). The fetal head is perfectly grasped only when the long axis of the blades corresponds to the occipitomental diameter (see Fig. 29-1). As a result, most of the blade lies over the lateral face. If the fetus is in an OA position, then the concave arch of the blades is directed toward the sagittal suture. If the fetus is in an occiput posterior (OP) position, then the concave arch is directed toward the midline face.

Suboptimal blade placement can increase morbidity (Ramphul, 2015). For OA position, appropriately applied blades are equidistant from the sagittal suture, and each blade is equidistant from its adjacent lambdoidal suture. In the OP position, the blades are equidistant from the midline of the face and brow. Also for OP position, blades are symmetrically placed relative to the sagittal suture and each coronal suture. Applied in this way, the forceps should not slip, and traction may be applied most advantageously. With most forceps, if one blade is applied over the brow and the other over the occiput, the instrument cannot be locked, or if locked, the blades will slip off when traction is applied (Fig. 29-8).

With both branches in place, it should be an easy matter to articulate the handles, engage the lock, and correct asynclitism if present. Asynclitism is resolved by pulling and/or pushing each branch along the long axis of the instrument until the finger guards align. If necessary, rotation to OA position is performed before traction is applied (Fig. 29-9).

When it is certain that the blades are placed satisfactorily, then gentle, intermittent, downward and outward traction is exerted concurrent with maternal efforts until the perineum begins to bulge. When the head is at 0 to +2 of +5 station, the initial direction of traction is quite posterior, almost toward the floor. With head descent, the vector of forces changes continuously (Fig. 29-10). As a teaching tool for this, a Bill axis traction device can be attached over the finger guards of most forceps. The instrument has an arrow and indicator line. When the arrow points directly to the line, traction is along the path of least resistance. With traction, as the vulva is distended by the occiput, an episiotomy may be performed if indicated. Additional horizontal traction is applied, and the handles are then gradually elevated. As the handles are raised, the head is extended. During the birth of the head, mechanisms of spontaneous delivery should be simulated as closely as possible.

The force produced by the forceps on the fetal skull is a function of both traction and compression by the forceps, as well as friction produced by maternal tissues. It is impossible to ascertain the amount of force exerted by forceps for an individual patient. Traction should therefore be intermittent, and the head should be allowed to recede between contractions, as in spontaneous labor. Except when urgently indicated, as in severe fetal bradycardia, delivery should be sufficiently slow, deliberate, and gentle to prevent undue head compression. It is preferable to apply traction only with each uterine contraction. Maternal pushing will augment these efforts.

After the vulva has been well distended by the head, the delivery may be completed in several ways. Some clinicians keep the forceps in place to control the head. If this is done, however, the blade volume adds to vulvar distention, thus increasing the likelihood of laceration or necessitating a large episiotomy. To prevent this, the forceps may be removed, and delivery is then completed by maternal pushing (Fig. 29-11). Importantly, if blades are disarticulated and removed too early, the head may recede and lead to a prolonged delivery. Delivery in some cases may be aided by addition of the modified Ritgen maneuver.

Occiput Posterior Positions

Prompt delivery may at times become necessary when the small occipital fontanel is directed toward one of the sacroiliac synchondroses. In these right OP (ROP) or left OP (LOP) positions, the fetal head is often imperfectly flexed. With OP positions, second-stage labor can be lengthened. In these cases, the head may spontaneously deliver OP, may be manually or instrumentally rotated to an OA position, or may be delivered OP by forceps or vacuum.

With manual rotation, an open hand is inserted into the vagina. The palm straddles the sagittal suture of the fetal head. The operator’s fingers wrap around one side of the fetal face and thumb extends along the other side. If the occiput is ROP, rotation is clockwise to bring it to an ROA or OA position (Fig. 29-12). With LOP position, rotation is counterclockwise. Three actions are performed simultaneously between contractions. The first is fetal head flexion to provide a smaller diameter for rotation and subsequent descent. Second, slight destationing of the fetal head moves the head to a level in the maternal pelvis with sufficient room to complete the rotation. Importantly, destationing should not be confused with disengaging the fetal head, which is proscribed. Concurrently, some prefer to also place the other hand externally on the corresponding side of the maternal abdomen to pull the fetal back up toward the midline in synchrony with the internal rotation. Le Ray and colleagues (2007, 2013) reported a success rate of greater than 90 percent with manual rotation. Barth (2015) provides an excellent summary of this technique.

Manual rotations are most easily completed in multiparas. If manual rotation cannot be easily accomplished, application of forceps blades to the head in the posterior position and delivery from an OP position may be the safest procedure. In many cases, the cause of a persistent OP position and of the difficulty in accomplishing rotation is an anthropoid pelvis. This architecture opposes rotation and predisposes to posterior delivery (Fig. 2-17).

With forceps delivery from an OP position, downward and outward traction is applied until the base of the nose passes under the symphysis (Fig. 29-13). The handles are then slowly elevated until the occiput gradually emerges over the upper margin of the perineum. The forceps are directed downward again, and the nose, mouth, and chin successively emerge from the vulva.

OP delivery causes greater distention of the vulva, and a large episiotomy may be needed. OP deliveries have a higher incidence of severe perineal lacerations and extensive episiotomy compared with OA positions (de Leeuw, 2008; Pearl, 1993). Also, newborns delivered from OP positions have a higher incidence of Erb and facial nerve palsies, 1 and 2 percent, respectively, than those delivered from OA positions. As expected, rotations to OA ultimately decrease perineal delivery trauma (Bradley, 2013).

Last, for forceps rotations from an OP to OA position, the Kielland instruments are preferred because they have a less pronounced pelvic curve (Fig. 29-14). Cunningham and Gilstrap’s Operative Obstetrics, 3rd edition, offers a more detailed description of this Kielland forceps procedure (Yeomans, 2017).

Occiput Transverse Positions

With occiput transverse (OT) positions, rotation is required for delivery. With experienced operators, high success rates with minimal maternal morbidity can be achieved (Burke, 2012; Stock, 2013). Either standard forceps, such as Simpson, or specialized forceps, such as Kielland, are employed. With Kielland forceps, each handle has a small knob, and branches are placed so that this knob faces the occiput. The station of the fetal head must be accurately determined to be at, or preferably below, the level of the ischial spines, especially in the presence of extreme molding.

Kielland described two methods of applying the anterior blade. In our example, placement with a left OT (LOT) position is described. With the wandering method, the anterior blade is first introduced into the posterior pelvis (Fig. 29-15). The blade is then arched around the face to an anterior position. To permit this sweep of the blade, the handle is held close to the maternal left buttock throughout the maneuver. The second blade is introduced directly posteriorly, and the branches are locked.

After checking the application, the handles of the Kielland forceps are pulled slightly to the patient’s right to increase fetal head flexion and create a smaller diameter for rotation. The first and second fingers of the left hand are placed over the finger guards with the palm against the handles. This palm faces the maternal left. Concurrently, the first two fingers of the operator’s right hand are placed against the anterior lambdoid suture. The fetal head is then destationed approximately 1 cm. For rotation in a counterclockwise direction, the wrist of the left hand supinates, to direct this palm upward. Simultaneously, two fingers of the right hand press on the edge of the right parietal bone that borders the lambdoid suture. This ensures that the fetal head turns with the blades and does not slip.

The second type of blade application introduces the anterior blade with its cephalic curve directed upward to curve under the symphysis. After it has been advanced far enough toward the upper vagina, it is turned on its long axis through 180 degrees to adapt the cephalic curvature to the head.

With either application, after rotation completion, the operator may choose from two acceptable methods for delivery. In one, the operator applies traction on the Kielland forceps using a bimanual grip described previously for conventional forceps (Forceps Delivery). When the posterior fontanel has passed under the subpubic arch, the handles can be elevated to the horizontal. Raising the handles above the horizontal may cause vaginal sulcus tears because of the reverse pelvic curve (Dennen, 1955). Alternatively, the Kielland forceps can be removed after rotation and replaced with conventional forceps. With this approach, moderate traction is first employed to seat the head before switching instruments.

Face Presentations

With a mentum anterior face presentation, forceps can be used to effect vaginal delivery. The blades are applied to the sides of the head along the occipitomental diameter, with the pelvic curve directed toward the neck. Downward traction is exerted until the chin appears under the symphysis. Then, by an upward movement, the face is slowly extracted, with the nose, eyes, brow, and occiput appearing in succession over the anterior margin of the perineum. Forceps should not be applied to the mentum posterior presentation because vaginal delivery is impossible except in very small fetuses.

Vacuum Extractor Design

With vacuum delivery, suction is created within a cup placed on the fetal scalp such that traction on the cup aids fetal expulsion. In the United States, vacuum extractor is the preferred term, whereas in Europe it is commonly called a ventouse (Fig. 29-16). Theoretical benefits of this tool compared with forceps include simpler requirements for precise positioning on the fetal head and avoidance of space-occupying blades within the vagina, thereby mitigating maternal trauma.

Vacuum devices contain a cup, shaft, handle, and vacuum generator. Vacuum cups may be metal or hard or soft plastic, and they may also differ in their shape, size, and reusability. In the United States, nonmetal cups are generally preferred, and there are two main types. The soft cup is a pliable bell-shaped dome, whereas the rigid type has a firm flattened mushroom-shaped cup and circular ridge around the cup rim (Table 29-2). When compared, rigid mushroom cups generate significantly more traction force (Hofmeyr, 1990; Muise, 1993). With OP positions or with asynclitism, the flatter cup also permits improved placement at the flexion point, which is typically less accessible with these head positions. The trade-off is that the flatter cups have higher scalp laceration rates. Thus, many manufacturers recommend soft bell cups for more straightforward OA deliveries.

Several investigators have compared outcomes with various rigid and soft cups. Metal cups provide higher success rates but greater rates of scalp injuries, including cephalohematomas (O’Mahony, 2010). In another study, Kuit and coworkers (1993) found that the only advantage of the soft cups was a lower incidence of scalp injury. They reported a 14-percent episiotomy extension rate with both rigid and pliable cups. In a review, Vacca (2002) concluded that there were fewer scalp lacerations with the soft cup, but that the rate of cephalohematomas and subgaleal hemorrhage was similar between soft and rigid cups. Importantly, high-pressure vacuum generates large amounts of force regardless of the cup used (Duchon, 1998).

Aside from the cup, the shaft that connects the cup and handle may be flexible or semiflexible. Tubing-like flexible shafts may be preferred for OP positions or asynclitic presentation to permit better seating of the cup. Last, the vacuum generator may be handheld and actuated by the operator or may be held and operated by an assistant.

Technique

An important step in vacuum extraction is proper cup placement over the flexion point. This pivot point maximizes traction, minimizes cup detachment, flexes but averts twisting the fetal head, and delivers the smallest head diameter through the pelvic outlet. This improves success rates, lowers fetal scalp injury rates, and lessens perineal trauma because the smallest fetal head diameter distends the vulva (Baskett, 2008).

The flexion point is found along the sagittal suture, approximately 3 cm in front of the posterior fontanel and approximately 6 cm from the anterior fontanel. Because cup diameters range from 5 to 6 cm, when properly placed, the cup rim lies 3 cm from the anterior fontanel (Fig. 29-17). Placement of the cup more anteriorly on the fetal cranium—near the anterior fontanel—should be avoided as it leads to cervical spine extension during traction unless the fetus is small. Such placement also delivers a wider fetal head diameter through the vaginal opening. Last, asymmetrical placement relative to the sagittal suture may worsen asynclitism. For elective use, cup placement in OA positions is seldom difficult. In contrast, when the indication for delivery is failure to descend caused by occipital malposition— with or without asynclitism or deflexion—cup positioning can be difficult.

During cup placement, maternal soft tissue entrapment predisposes the mother to lacerations and virtually ensures cup dislodgement, colloquially called a “pop off.” Thus, the entire cup circumference should be palpated both before and after the vacuum has been created and again prior to traction to exclude such entrapment. Gradual vacuum creation is advocated by some and is generated by increasing the suction in increments of 0.2 kg/cm² every 2 minutes until a total negative pressure of 0.8 kg/cm² is reached (Table 29-3). That said, other studies have shown that negative pressure can be increased to 0.8 kg/cm² in <2 minutes without a significant difference in efficacy or in maternal and fetal outcomes (Suwannachat, 2011, 2012).

Once suction is created, the instrument handle is grasped, and traction is initiated. Similar to forceps delivery, traction angles mirror that in Figure 29-10. Efforts are intermittent and coordinated with maternal expulsive efforts. Manual torque to the cup is avoided as it can cause cup displacement or cephalohematomas and, with metal cups, “cookie-cutter”–type scalp lacerations. Thus, OA oblique positions are corrected not by rotation, but solely by downward outward traction. During pulls, the operator should place the nondominant hand within the vagina, with the thumb on the extractor cup and one or more fingers on the fetal scalp. So positioned, descent of the presenting part can be judged and the traction angle can be adjusted with head descent. In addition, the relationship of the cup edge to the scalp can be assessed to help detect cup separation.

Between contractions, some physicians will lower the suction levels to decrease rates of scalp injury, whereas others will maintain suction in cases with a nonreassuring fetal heart rate to aid rapid delivery. No differences in maternal or fetal outcome were noted if the level of vacuum was decreased between contractions or if an effort was made to prevent fetal loss of station (Bofill, 1997). Once the head is extracted, the vacuum pressure is relieved and the cup removed.

Vacuum extraction should be considered a trial. Without early and clear evidence of descent toward delivery, an alternative delivery approach should be considered. As a general guideline, progressive descent should accompany each traction attempt. Neither data nor consensus are available regarding the number of pulls required to effect delivery, the maximum number of cup pop-offs that can be tolerated, or optimal total duration of the procedure. Some manufacturers have recommendations regarding these in their instructional literature (Clinical Innovations, 2016; CooperSurgical, 2011).

During a vacuum extraction trial, cup dislodgement due to technical failure or less than optimal placement should not be equated with dislodgement under ideal conditions of exact cup placement and optimal vacuum maintenance. These cases may merit either additional attempts at placement or, alternatively, a trial of forceps (Ezenagu, 1999; Williams, 1991). The least desirable cases are those in which traction without progress or multiple disengagements occur following correct cup application and appropriate traction. As with forceps, clinicians should embrace a willingness to abandon attempts at vacuum extraction if satisfactory progress is not made (American College of Obstetricians and Gynecologists, 2015).