Key Abbreviations
American College of Obstetricians and Gynecologists ACOG
Anteroposterior AP
Biparietal diameter BPD
Body mass index BMI
Confidence interval CI
Disseminated intravascular coagulation DIC
Food and Drug Administration FDA
Intracranial hemorrhage ICH
Intelligence quotient IQ
Left occiput anterior LOA
Left occiput posterior LOP
Neonatal intensive care unit NICU
Occiput anterior OA
Occiput posterior OP
Occiput transverse OT
Odds ratio OR
Randomized controlled trial RCT
Relative risk RR
Right occiput anterior ROA
Obstetric forceps are the one instrument that makes the practice of obstetric care unique to obstetricians. The proper use of these instruments has afforded safe and timely vaginal delivery to those whose abnormal labor course and/or urgent need for delivery required their use.
Following the introduction of forceps by Chamberlin during the 1600s, much discussion about the proper use and timing of forceps application ensued. After Smellie’s retirement from practice in 1760, forceps began to be used more frequently, resulting in an increase in both maternal and neonatal injury owing to the application techniques common at the time. In his 1788 text entitled “An Introduction to the Practice of Midwifery,” Thomas Denman stated that “the head of the child shall have rested for 6 hours as low as the perineum before the forceps are applied though the pains should have ceased during that time.” Denman’s law then became widely accepted as the standard of this time. However, after the news of Princess Charlotte’s death following the birth of a stillborn Prince on November 6, 1817, a review of Denman’s law ensued with much public discussion regarding the timely use of forceps. Princess Charlotte’s labor had been managed by one of Denman’s students and son-in-law, Sir Richard Croft, whose second-stage labor management during this delivery came into question. Croft had permitted the second stage to last 24 hours, including 6 hours on the perineum, as Denman’s law had advised. However, the Princess delivered a 9 lb stillborn male heir, and within 24 hours of delivery, the Princess herself died of a massive postpartum hemorrhage. Disturbed with depression and despair at the blame for the death of both the Princess and the heir to the British throne, Croft shot himself 3 months later. During a lecture delivered at the Royal College of Obstetricians and Gynaecologists (RCOG) on September 28, 1951, Sir Eardley Holland named his lecture on these events “A Triple Obstetric Tragedy” in which he described a mother, baby, and accoucheur all dead, victims of a mistaken system. In a subsequent text in 1817, Denman wrote: “Care is also to be taken that we do not, through an aversion to the use of instruments, too long delay that assistance we have the power of affording them.” The debate regarding the use of these instruments continued into the twentieth century with prophylactic forceps delivery advocated by DeLee in 1920. This clinical management strategy resulted in forceps delivery rates in excess of 65% by 1950.
With these lessons in mind, a review of operative vaginal delivery in modern obstetric practice is extremely important and timely. Rates of cesarean delivery have risen in both the United States and the United Kingdom, increasing 60% between 1996 and 2009 in the United States, when the rate reached 32.9%—the highest rate ever reported—and increasing 100% between 1990 and 2008 (12% to 24%) in the United Kingdom. Between 2009 and 2013, the rate of cesarean delivery in the United States has declined only slightly to 32.7%. In contrast, rates of forceps and vacuum extraction to assist delivery have decreased dramatically from 9% in 1990 to 3.4% in 2012. Forceps have been used for fewer than 1% of all births in the United States since 2005 (0.59% in 2013). However, most residency training programs in the United States still expect proficiency in outlet and low forceps delivery (less than or greater than a 45-degree rotation), whereas less than 40% expect proficiency in midforceps delivery. However, to make education and teaching of these procedures even more challenging, new resident work hour restrictions have resulted in a decline in resident experience with both primary cesarean delivery and vacuum-assisted vaginal delivery despite increased institutional volumes of these procedures. In a study by Blanchard and colleagues, the decrease in experience was shown to be dramatic: they noted a 54% decline in experience with primary cesarean delivery and a 56% decline in vacuum-assisted vaginal delivery. Because both forceps and vacuum extractors are acceptable and safe instruments for operative vaginal delivery, operator experience is the determining factor in deciding which instrument should be used in a specific clinical situation. Declining use and resident experience may make it difficult to provide the level of operator skills required for proficiency of this obstetric art. However, because most women prefer a vaginal delivery, focused experience with the use of these instruments during residency training is crucial to ensure safe, timely, and effective vaginal delivery. Furthermore, women are more likely to achieve a spontaneous vaginal delivery in a subsequent pregnancy after forceps delivery than after cesarean delivery (78% vs. 31%). The challenge, therefore, is to ensure that women who experience second-stage labor abnormalities are afforded all options for a safe and timely delivery.
Operative Vaginal Delivery
Classification, Prerequisites, and Indications
The use of a well-defined and consistent classification system for operative vaginal deliveries facilitates the comparison of maternal and neonatal outcomes among spontaneous delivery, cesarean delivery, and operative vaginal delivery as well as instruction in these techniques. It is intuitive that not all operative vaginal deliveries are the same with respect to degree of difficulty or maternal and fetal risk; therefore classification systems have been developed and modified over time. In 1949, Titus created a classification system that permitted general practitioners to perform operative vaginal delivery without consultation from a specialist. This system divided the pelvis into thirds from the ischial spines to the inlet and, in the opposite direction, in thirds to the outlet. Dennen proposed an alternative classification system in 1952 that was based on the four major obstetric planes of the pelvis with the following definitions: high forceps is the biparietal diameter (BPD) in the plane of the inlet but above the ischial spines; midforceps is the BPD just at or below the ischial spines and the sacral hollow not filled; low midforceps is the BPD below the ischial spines, the leading bony part within a fingerbreadth of the perineum between contractions, and the hollow of the sacrum filled; and outlet forceps is the BPD below the level of the ischial spines, the sagittal suture in the anteroposterior diameter, and the head visible at the perineum during a contraction.
In 1965, the American College of Obstetricians and Gynecologists (ACOG) created a classification system that defined midforceps extremely broadly, from the ischial spines to the pelvic floor and any rotation. This category clearly included many forceps operations that ranged from delivery of a straightforward anteroposterior position of the fetal vertex to complex rotations. The broad category for these operations led many practicing clinicians to question whether the classification should be narrowed to reflect the clinically significant differences between deliveries such as these.
In 1988, ACOG revised the classification of forceps operations to address two significant shortcomings of the previous system: that midforceps was too widely defined and outlet forceps was too narrowly defined. This system was validated in 1991 by Hagadorn-Freathy and colleagues, who demonstrated that 25% of deliveries in this study that would have been previously classified as midforceps but were reclassified into the low forceps (greater than 45-degree rotation) and midforceps categories were associated with 41% of episiotomy extensions and 50% of the lacerations in the cohort. Clearly, the outcomes of these operations confounded the relatively low-risk group of low-forceps operations with up to 45-degree rotation, which would also have been classified as midforceps by the previous system. In short, these investigators validated the 1988 ACOG classification scheme by demonstrating that the higher station and more complex deliveries carried a greater risk of maternal and fetal injury compared with those that were more straightforward. This differentiation was lost in the 1965 classification scheme owing to the broad definition of low forceps . It is extremely important to appropriately classify operative vaginal delivery based on this system, including accurate determination of fetal station and position. The 1988 classification scheme for operative vaginal delivery is shown in Box 14-1 .
Outlet
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Scalp is visible at the introitus without separating the labia.
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Fetal skull has reached the pelvic floor.
- •
Sagittal suture is in the AP diameter or LOA/ROA or LOP/ROP positions.
- •
Fetal head is at or on the perineum.
- •
Rotation does not exceed 45 degrees.
Low Forceps
- •
Leading point of fetal skull is at +2 cm or greater and not on the pelvic floor.
- •
Rotation 45 degrees or less to LOA/ROA to OA or LOP/ROP to OP, or rotation is 45 degrees or more.
Midforceps
- •
Station is above +2 cm but head is engaged.
High
- •
High forceps delivery is not included in this classification.
AP, anteroposterior; LOA, left occiput anterior; LOP, occiput posterior; OA, occiput anterior; OP, occiput posterior; ROA, right occiput anterior; ROP, occiput posterior.
With respect to operative vaginal delivery of the vertex, station is defined as the relationship of the estimated distance in centimeters between the leading bony portion of the fetal head and the level of the maternal ischial spines, and position refers to the relationship of the occiput to a denominating location on the maternal pelvis. Operative vaginal delivery with a fetus in the left occiput anterior (LOA) position with the leading bony portion of the vertex 3 cm below the ischial spines (+3 station) would be classified as low forceps, less than 45-degree rotation delivery. It is also important to note that this classification system applies to both forceps and vacuum extraction instruments and that the precise position and station must be known before the placement of either instrument.
In addition to precise evaluation of the position and station, several other extremely important data are necessary before performing an operative vaginal delivery. The prerequisites for application of either forceps or vacuum extractor are listed in Table 14-1 . When these prerequisites have been met, the following two indications are appropriate for consideration of either forceps delivery or vacuum extraction: (1) prolonged second stage (for nulliparous women, lack of continuing progress for 3 hours with regional analgesia or 2 hours without regional analgesia; for multiparous women, lack of continuing progress for 2 hours with regional analgesia or 1 hour without regional analgesia) and ( 2) suspicion of immediate or potential fetal compromise (nonreassuring fetal heart rate tracing or shortening of the second stage of labor for maternal benefit [i.e., maternal exhaustion, maternal cardiopulmonary or cerebrovascular disease]).
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Operative Vaginal Delivery Instruments
Forceps Instruments
Invention and modification have led to a description and use of more than 700 varieties of forceps instruments. Most of them are of historic interest only, but many common features remain among those still in use. Except when used at cesarean delivery, forceps are paired instruments and are broadly categorized according to their intended use as classic forceps, rotational forceps, and specialized forceps designed to assist vaginal breech deliveries. Each forceps type consists of two halves joined by a lock, which may be sliding or fixed. The key structures of forceps include the blade, shank, lock, finger guards, and handle ( Fig. 14-1 ). The toe refers to the tip of the blade, and the heel is the end of the blade that is attached to the shank at the posterior lip of the fenestration (if present). The cephalic curve is defined by the radius of the two blades when in opposition, and the pelvic curve is defined by the upward—or reverse, as in the case of Kielland and Piper forceps—curve of the blades from the shank. The handles transmit the applied force, the screw or lock represents the fulcrum, and the blades transmit the load ( Fig. 14-2 ).
The pelvic curve permits ease of application along the maternal pelvic axis ( Fig. 14-3 ). Forceps have two functions, traction and rotation, both of which can only be accomplished by some degree of compression on the fetal head. The cephalic curvature of the blade is designed to aid in the even distribution of force about the fetal parietal bone and malar eminence. Blades may be solid (Tucker-McLane), fenestrated (Simpson), or pseudofenestrated (Luikart-Simpson). The pseudofenestration modification can be applied to the design of any type of forceps and is known as the Luikart modification. In general, use of solid or pseudofenestrated blades results in less risk of maternal soft tissue injury, especially during rotation, but fenestrated blades provide improved traction in comparison to solid blades.
Classic Forceps
Classic forceps instruments are typically used when rotation of the vertex is not required for delivery. However, they may be used for rotations such as the Scanzoni-Smellie maneuver. All classic forceps have a cephalic curve, a pelvic curve, and an English lock, in which the articulation is fixed in a slot into which the shank of the opposite blade fits. The type of classic forceps instrument is determined by its shank, whether overlapping or parallel. Examples of classic forceps with parallel shanks include Simpson, DeLee, Irving, and Hawks-Dennen forceps. Classic forceps with overlapping shanks include Elliott and Tucker-McLane. Because these instruments have a more rounded cephalic curve than the Simpson forceps, they are often used for assisting delivery of the unmolded head, such as that commonly encountered in the multiparous patient. In addition, because the Tucker-McLane forceps have a shorter, solid blade and overlapping shanks, they are more often used for rotations than other classic instruments.
Rotational Forceps
Forceps instruments used for rotation are characterized as having a cephalic curve amenable to application to the molded vertex and either only a slight pelvic curve or none at all. The absence of a pelvic curve in these instruments facilitates rotation of the vertex without moving the handles of the instrument through a wide arc, as is necessary when using one of the classic instruments to accomplish rotation. Forceps that may be used for rotation include some of the classic instruments (e.g., Tucker-McLane) and those with minimal pelvic curvature (e.g., Kielland and Leff). In 1916, Christian Kielland of Norway described the rationale for the introduction of his new forceps :
When the head is high, it has to be pulled through a greater length of the birth canal, which is incompletely prepared. The child’s head is in such a position that it cannot be grasped by the blades of the forceps in the way that is possible when the head is low and completely rotated. The forceps do not hold the head in the biparietal diameter but over the occipital and frontal areas, which cannot withstand much pressure. These factors are responsible for the difficulties that occur in such a delivery, but they do not entirely explain the amount of force required nor the resistance encountered. In the search for an explanation of the chief cause for the remarkable amount of force that had to be used, it was thought that traction might be in the wrong direction, because the blade of the ordinary forceps is curved to correspond with the birth canal. This type of forceps cannot be depressed sufficiently low against the perineum without the risk of damaging it or losing the good position on the fetal head when an attempt is made to exert traction in the pelvic axis.
After their introduction, Kielland forceps have become a frequently used instrument for rotation of the vertex (see Fig. 14-1 ). These forceps have a slightly backward pelvic curve with overlapping shanks and a sliding lock. The advantages of the Kielland forceps, compared with the classic instruments for rotation, include the following:
- •
The straight design places the handle and shanks in the same plane as the long axis of the fetal head, permitting the toe to travel through a very small arc during rotation.
- •
The distance between the heel and the intersecting point of the shanks is long, which accommodates heads of various shapes and sizes, associated with unusual molding.
- •
A slight degree of axis traction is produced by the reverse pelvic curve.
- •
The sliding lock permits placement of the handles at any level on the shank to accommodate the asynclitic head and subsequent correction of asynclitism.
In 1955, another forceps used for rotation of the vertex was introduced by Leff. These forceps have a locking shank with short, straight, and narrow blades and a smaller cephalic curve than the Kielland forceps. In a series of 104 consecutive rotational forceps deliveries (>90 degrees) using Leff forceps, compared with 163 nonrotational forceps deliveries with traditional instruments, Feldman and colleagues demonstrated a lower episiotomy rate (66% vs. 82%) and a lower perineal laceration rate (16% vs. 23%) with the Leff forceps compared with the nonrotational forceps group, attributed to a 40% spontaneous vaginal delivery rate after Leff forceps rotation. In addition, no difference was reported in the low incidence of fetal bruising between the groups (3% in each). They concluded that Leff forceps were also a safe option for rotation of the persistent occiput posterior (OP) fetal position.
Other Specialized Instruments
Forceps to assist with delivery of the aftercoming head during vaginal breech delivery (Piper forceps) have a cephalic curve, a reverse pelvic curve, long parallel shanks, and an English lock (see Fig. 14-2 ). This design provides easy application to the aftercoming head, stabilizing and protecting the fetal head and neck during delivery. The long shanks permit the body of the breech to rest against it during delivery of the head (see Chapter 17 ).
Vacuum Extraction Devices
Swedish obstetrician Tage Malmström is credited with the introduction of the first successful vacuum cup into the field of modern obstetrics in 1953. It consisted of a metal cup, suction tubing, and a traction chain. Vacuum devices are classified by the material used to make the cup, either stainless steel or plastic (silicone). So-called soft (plastic) cups are used much more commonly in the United States than the stainless steel cups owing to the lower rates of scalp trauma associated with these devices, which consist of a cup connected to a handle grip with tubing that connects them both to a vacuum source ( Fig. 14-4 ). The vacuum generated through this tubing attaches the fetal scalp to the cup and allows traction on the vertex. The vacuum force can be generated either from wall suction or by a handheld device with a pumping mechanism.
Stainless Steel Devices
The Malmström device is the most commonly used instrument for vacuum extraction in the world. This device consists of a mushroom-shaped stainless steel cup, two vacuum hoses, a traction chain and attached metallic disk, a traction handle, and a vacuum source. The cup is available in 40, 50, and 60 mm diameter sizes and is designed such that the diameter of the opening is smaller than the internal diameter of the cup. Therefore when vacuum is established, the fetal scalp fills the internal dimension of the cup, and an artificial caput succedaneum is formed (the “chignon”). This allows for the appropriate traction force to be applied to the vertex without a “pop-off” or detachment.
Soft-Cup Devices
These devices may be classified into three groups by the shape of the cup: funnel shaped, bell shaped, and mushroom shaped ( Figs. 14-5 and 14-6 ). The Kobayashi style funnel-shaped Silastic cup is the prototype and the largest cup available (65 mm). It was designed to fit over the fetal occiput without requiring formation of a chignon. This feature results in a lower rate of scalp trauma and more rapid time to effect delivery compared with the stainless steel devices but with a slightly higher failure rate owing to pop-off. Bell-shaped cups are available from a number of vendors and include the MityVac (Prism Enterprises), Kiwi (Clinical Innovations), and CMI (Utah Medical). The mushroom-shaped cups are a hybrid of the stainless steel and plastic devices. Examples of these devices include the M-cup (MityVac), OmniCup (Kiwi), and Flex Cup (CMI). The maneuverability of these devices is superior to either the funnel-shaped or bell-shaped devices owing to their smaller size and increased flexibility of the traction stem relative to the cup. However, like other vacuum devices, they are still limited in their use for either OP or occiput transverse (OT) positions owing to an inability to achieve the proper median flexing application. Advances to the Kiwi product have resulted in a style of cup in which the stem is completely collapsible against the cup (see Fig. 14-5 ), thus allowing placement of the vacuum on the point of flexion of the head that is asynclitic or in the OP position.
Operative Vaginal Delivery Techniques
Classic Forceps: Application for Occiput Anterior and Occiput Posterior Positions
Forceps blades are labeled left and right based on the maternal side into which they are placed. For example, the left blade refers to the maternal left side, and its handle is held in the operator’s left hand for placement (see Fig. 14-3 ). The posterior blade is conventionally placed first because it provides a splint for the fetal head to prevent rotation from the occiput anterior (OA) position to a more OP position when the second blade is applied. Therefore when the fetus is OA to LOA, the left blade is placed first. The operator holds the handle of the left blade in his or her left hand with the toe of the blade directed toward the floor. With the plane of the shank perpendicular to the floor, the cephalic curve of the blade is to be applied to the curve of the fetal head. To protect the vaginal sidewalls, the fingers of the right hand are placed within the left vagina with the palm of the hand facing the fetal skull. The cephalic curve of the blade should lie evenly against the fetal skull as the toe of the blade is placed at approximately 6 o’clock. The operator’s right thumb guides the heel of the blade and the right index finger guides the toe of the blade gently over the left parietal bone. The handle of the blade should be held lightly with the left thumb and index finger. As the blade is inserted into the pelvis, its shank and handle are to be rotated counterclockwise toward the right maternal thigh and then inward toward the maternal midline. This movement will guide the toe of the blade over the left parietal bone and onto the left malar eminence. The force applied by the left thumb and index finger on the handle should be minimal as the blade enters the maternal pelvis. If there is anything more than very light or slight resistance to blade entry into the maternal pelvis, the blade should be removed and the application technique reevaluated. Once the blade has been applied, an assistant may hold it in place. To place the right blade, this process is repeated with opposite hands doing the maneuvers described earlier.
When the fetus is in a right occiput anterior (ROA) position, the right fetal parietal bone is located in the posterior maternal pelvis so the posterior blade will be the right blade, and this is placed first. Once both blades are in place, if the handles do not lock easily, the application is incorrect. The blades should have a bimalar, biparietal placement when applied properly ( Fig. 14-7 ). Once the handles are locked, proper blade location must be confirmed. Identification of the posterior fontanel, sagittal suture, lambdoid sutures, and blade fenestrations enable the operator to confirm proper forceps blade placement before their use. The three criteria needed to confirm proper forceps application are (1) the posterior fontanel should be one fingerbreath above the plane of the shanks and midway between the blades, or the lambdoid sutures (or anterior fontanel for the OP fetus) should be equidistant from the upper edge of each blade; (2) the sagittal suture should be perpendicular to the plane of the shanks; and (3) if using fenestrated blades, the fenestrations should be barely palpable. The operator should not be able to place more than one fingertip between the fenestration and the fetal head.
The direction of traction on the fetal head is determined by the station of the BPD (see Fig. 14-3 ). For example, higher fetal stations require a steeper angle of traction below the horizontal. The shape of the maternal pelvis may be visualized as the terminal end of the letter “J.” As the fetal head descends within the pelvis, the axis of traction follows a curved line upward from the floor. The axis of traction rises above the horizontal as the fetal head crowns and extends just as the head does in a spontaneous vaginal delivery. With the axis traction principle, force is directed in two vectors—downward and outward. One hand holds the shanks and exerts downward traction while the operator’s other hand holds the handles and exerts traction outward. As the vertex descends and exits, there will be a natural extension of the fetal head, and the forceps should guide the vertex through this pathway in such a fashion that the forceps handle will curve anteriorly relative to the patient, with the forceps handle nearly anterior to the pubic symphysis. An alternative method is to use it as an axis traction instrument; this attachment may be joined to the handle to facilitate traction below the handles in the line of the pelvic axis (see Fig. 14-3 ) and allows the forceps to follow the natural extension of the fetal head. Forceps traction should begin with the uterine contraction and should coincide with maternal pushing efforts until the contraction ends. Fetal heart tones should be monitored. Descent should occur with each pull, and if no descent occurs after two to three pulls, the operative delivery should be halted and measures should be taken to proceed with cesarean delivery. (See for an example of the technique of forceps application and delivery.) Switching to a vacuum should be done very cautiously (see “ Sequential Use of Vacuum and Forceps ” later in this chapter).
Forceps may also be appropriate for OP, left occiput posterior (LOP), or right occiput posterior (ROP) positions if the station of the bony part of the head is truly at least +2 station. Infants in persistent OP position represent a unique challenge. With a deflexed or extended head, a wider diameter presents through the pelvic outlet, which requires more force for descent of the fetal head. Proper assessment of fetal station can be made complex by extension and molding of the head. With fetal molding, the widest diameter of the fetal head may be at a much higher station than the leading bony part, thus making traction within the proper pelvic axis difficult to ascertain. The tendency is to overestimate station in OP positions, so the operator must be confident in their station assessment.
Rotational Forceps: Application for Occiput Transverse Positions
Rotation must be accomplished from the OT position before delivery of the fetal head. This may happen spontaneously, with manual assistance, or with use of forceps when appropriate. The reader is referred to Dennen’s Forceps Deliveries for a more extensive review of forceps rotation techniques. Forceps rotations should be attempted only with an experienced operator.
Classic Forceps
For left occiput transverse (LOT) positions, the posterior left blade should be applied first. The toe of the blade is placed at 6 o’clock, and the cephalic curve is applied to the fetal head. The handle is lowered to facilitate blade entry into the posterior pelvis and rests below the horizontal, the degree of which will be determined by fetal station. The anterior right blade is known as the wandering blade, and it is inserted with the right hand posteriorly at approximately 7 o’clock. Upward pressure on the blade is exerted with the fingers of the left hand as the right hand moves the handle in a clockwise arc across the left thigh toward the floor. The toe of the blade “wanders” from posterior to anterior, around the frontal bone, to rest anterior to the right ear. Elevation of the handle of the right blade permits movement of the blade further into the pelvis beyond the symphysis and articulation at the handles. The proper attitude of flexion is created by moving the handles toward the pelvic midline. Rotation of the fetal head is accomplished by counterclockwise rotation of the handles in a wide arc across the left thigh toward 12 o’clock. With classic forceps, a wide rotational arc at the handles produces the desired smaller arc of rotation at the toe of the blades. Once the OA position is reached, the blades may be readjusted before the generation of traction. This same procedure may be used for the right occiput transverse (ROT) position with classic forceps. In this instance, however, the right blade is posterior and should be applied first.
Kielland Forceps
Kielland forceps were originally designed for delivery of the fetal head in deep transverse arrest. They are now also used for rotation of the fetal head from OP or OT positions. The advantage of Kielland forceps lies in the reverse pelvic curve, which permits placement of the blades in the direct OT position without elevation of the fetal head and loss of station. Unlike classic forceps, with Kielland forceps the anterior blade is applied first. Three methods of Kielland forceps application have been described: (1) the inversion method, or classic application, (2) the wandering method, and (3) the direct method.
The inversion method may be used in OT and LOP or ROP positions. In an LOT position, the right anterior blade is gently guided below the symphysis with assistance from the operator’s left hand. With this application, the cephalic curve is facing up and beyond the symphysis, the handle is dropped below the horizontal, and the blade is rotated 180 degrees toward the midline until the cephalic curve rests on the parietal bone and malar eminence. If resistance is met with the inversion technique, the wandering technique may be used.
The wandering method for Kielland forceps is similar to that used for classic forceps. It requires initial placement of the anterior blade onto the posterior parietal bone with the cephalic curve directly applied to the fetus. The blade is then gently advanced around the face and frontal bone until it rests above the anterior fetal ear.
The direct method of application is preferred when the head is at low fetal station near the pelvic outlet. If the anterior ear is palpable beyond the symphysis, the forceps may be directly applied, often with less difficulty than with the other two methods. With the cephalic curve facing the fetus, the blade is applied by lowering the handle toward the floor. The toe is then gently advanced with guidance from the operator’s opposite hand, and the posterior blade is inserted at 6 o’clock with the cephalic curve facing the fetal skull; the operator’s free hand is inserted into the posterior pelvis palm side up, and the blade is gently guided into position over the posterior ear. The sliding lock will permit closure of the blades and correction of asynclitism, when the axis of the fetal head is oriented obliquely to the axial planes of the pelvis (see Chapter 12 ). Unlike rotation with classic forceps, the reverse pelvic curve of Kielland forceps permits rotation directly on the axis of the shanks. The shanks and handles are rotated around the midline point of application and should be held during rotation in a plane perpendicular to the plane of the fetal BPD. In some instances, the fetal head may need to be elevated and even disengaged to accomplish the rotation. This is performed by keeping the handles of the Kielland forceps well below the horizontal plane, pushing the forceps in an anterior-cephalad direction with respect to the maternal pelvis (e.g., toward the maternal umbilicus). Failure to angle in such a direction will result in the forceps making contact with the sacral promontory and an inability to achieve the room needed for rotation. During the rotation, one finger should follow the sutures to ensure that the forceps and fetal head move as a single unit. Generally speaking, use of one hand should provide sufficient force to complete the rotation and is a good guide for avoiding excess force. After successful rotation, proper forceps placement should be confirmed before downward traction is applied. Alternatively, the Kielland forceps could be removed, and classic forceps can be placed before traction. (See for a demonstration of Kielland forceps application and delivery.)
Forceps Rotation: Application for the Occiput Posterior Position
The fetal head may be rotated from OP to OA by use of the Scanzoni-Smellie technique using classic forceps. The posterior blade should be applied first and then appropriate placement of forceps should be confirmed. Minimal elevation of the fetal head upward within the pelvis will facilitate rotation. Movement of the handles in a wide arc toward the fetal back will enable rotation from the LOP position to OA. After rotation of the handles in a wide arc, the toe of the blades will be upside down with respect to the fetal malar eminence. They must then be removed and replaced properly before traction on the fetal head. Rotation from OP may also be accomplished with Kielland forceps. After successful rotation, traction can be applied for delivery of the fetal head.
Vacuum Extraction
As with forceps, successful use of the vacuum extractor is determined by proper application on the fetal head and traction within the pelvic axis. The leading point of the fetal head is the ideal position for vacuum cup placement. It is labeled the flexion point, or pivot point, and is located on the sagittal suture 2 to 3 cm below the posterior fontanel for the OA position and 2 to 3 cm above the posterior fontanel for the OP position. Placement of the vacuum cup over the pivot point maintains the attitude of flexion for a well-flexed head and creates flexion in a deflexed head if traction is applied correctly. Incorrect placement on an asynclitic head results in unequal distribution of force and increases the risk of neonatal intracranial injury and scalp lacerations. Therefore knowledge of exact fetal position is important for efficacious vacuum placement. The force generated by vacuum suction is substantial, with recommended pressures ranging from 550 to 600 mm Hg (11.6 psi). After initial placement of the cup, correct application must be confirmed, which includes determining that no vaginal tissue is caught beneath the vacuum cup before the vacuum pressure is raised to the desired level. Just as with forceps, traction should begin with each contraction and should coincide with maternal pushing efforts. Routine traction between contractions should be avoided. In the absence of maternal pushing, traction alone increases the force required for fetal descent and increases the risk of cup detachment. Twisting or rocking of the vacuum cup to facilitate descent of the fetal head is not recommended because of an increased risk of scalp laceration and intracranial hemorrhage (ICH). With correct application, traction in the pelvic axis often results in flexion and autorotation, depending on fetal station and the vacuum cup selected.
Detachment of the vacuum cup during traction should be viewed as an indication for reevaluation of the site of application, direction of axis traction, and fetal maternal pelvic dimensions. The rapid decompression that results from cup detachment for the soft and rigid vacuum cups has been associated with scalp injury, and it should not be viewed as a safety mechanism that is without potential for fetal risk. Data are limited to provide evidence-based support for the maximum duration of safe vacuum application, the maximum number of pulls required before delivery of the fetal head, and the maximum number of pop-offs or cup detachments before abandonment of the procedure. There is a general consensus, however, that descent of the fetal bony vertex should occur with each pull, and if no descent occurs after three pulls, the operative attempt should be stopped. Most authorities have recommended that the maximum number of cup detachments (pop-offs) be limited to two or three and that the duration of vacuum application before abandonment of the procedure be limited to a maximum of 20 to 30 minutes. A randomized controlled trial (RCT) compared maintenance of suction of 600 mm Hg throughout the operative delivery to reduction of suction to 100 mm Hg between contractions and found no differences in duration of operative delivery or in neonatal outcome. Finally, vacuum cup selection may play a role in the likelihood of successful vaginal delivery. The soft cup instruments used in modern practice are associated with less scalp trauma but have a higher failure rate than rigid metal vacuum cups. A meta-analysis of nine RCTs of soft versus rigid vacuum extractor cups determined that the average failure rates were 16% and 9% for the soft and metal cups, respectively, and the detachment rates were 22% and 10% for the soft and metal cups, respectively. Higher failure rates with the soft cup may be secondary to difficulties associated with proper placement and traction, particularly if the fetus is deflexed, malpositioned, or at higher station.
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