Key Abbreviations
Abdominal diameter AD
American College of Obstetricians and Gynecologists ACOG
Amniotic fluid index AFI
Anteroposterior AP
Biparietal diameter BPD
Cerebral palsy CP
Combined spinal-epidural CSE
Computed tomography CT
Confidence interval CI
External cephalic version ECV
Ex utero intrapartum treatment EXIT
Fetal heart rate FHR
Internal podalic version IPV
Magnetic resonance imaging MRI
Occipitofrontal diameter OFD
Odds ratio OR
Perinatal mortality rate PMR
Periventricular leukomalacia PVL
Preterm premature rupture of the membranes PPROM
Relative risk RR
Term breech trial TBT
Near term or during labor, the fetus normally assumes a vertical orientation, or lie, and a cephalic presentation, with the flexed fetal vertex presenting to the pelvis ( Fig. 17-1 ). However, in about 3% to 5% of singleton gestations at term, an abnormal lie, presentation, or flexed attitude occurs; such deviations constitute fetal malpresentations. The word malpresentation suggests the possibility of adverse consequences, and malpresentation is often associated with increased risk to both the mother and the fetus. In the early twentieth century, malpresentation often led to a variety of maneuvers intended to facilitate vaginal delivery, including destructive operations leading, predictably, to fetal death. Later, manual or instrumented attempts to convert the malpresenting fetus to a more favorable orientation were devised. Internal podalic version (IPV) followed by a complete breech extraction was once advocated as a solution to many malpresentation situations. However, like with most manipulative efforts to achieve vaginal delivery, IPV was associated with high fetal and maternal morbidity and mortality rates and has been largely abandoned. In contemporary practice, cesarean delivery has become the recommended mode of delivery in the malpresenting fetus.
Clinical Circumstances Associated with Malpresentation
Generally, factors associated with malpresentation include (1) diminished vertical polarity of the uterine cavity, (2) increased or decreased fetal mobility, (3) obstructed pelvic inlet, (4) fetal malformation, and (5) prematurity. The association of great parity with malpresentation is presumably related to laxity of maternal abdominal musculature and resultant loss of the normal vertical orientation of the uterine cavity. Placentation either high in the fundus or low in the pelvis ( Fig. 17-2 ) is another factor that diminishes the likelihood of a fetus assuming a longitudinal axis. Uterine myomata, intrauterine synechiae, and müllerian duct fusion abnormalities such as a septate uterus or uterine didelphys are similarly associated with a higher than expected rate of malpresentation. Because both prematurity and polyhydramnios permit increased fetal mobility, the probability of a noncephalic presentation is greater if preterm labor or rupture of the membranes occurs. Furthermore, preterm birth involves a fetus that is small relative to the maternal pelvis; therefore engagement and descent with labor or rupture of the membranes can occur despite a malpresentation. In contrast, conditions such as chromosomal aneuploidies, congenital myotonic dystrophy, joint contractures from various etiologies, arthrogryposis, oligohydramnios, and fetal neurologic dysfunction that result in decreased fetal muscle tone, strength, or activity are also associated with an increased incidence of fetal malpresentation. Finally, the cephalopelvic disproportion associated with severe fetal hydrocephalus or with a contracted maternal pelvis may be implicated as an etiology of malpresentation because normal engagement of the fetal head is prevented.
Abnormal Axial Lie
The fetal lie indicates the orientation of the fetal spine relative to the spine of the mother. The normal fetal lie is longitudinal and by itself does not indicate whether the presentation is cephalic or breech. If the fetal spine or long axis crosses that of the mother, the fetus may be said to occupy a transverse or oblique lie ( Fig. 17-3 ), which may cause an arm, foot, or shoulder to be the presenting part ( Fig. 17-4 ). The lie may be termed unstable if the fetal membranes are intact and fetal mobility is increased, which results in frequent changes of lie and/or presentation.
Abnormal fetal lie is diagnosed in approximately 1 in 300 cases, or 0.33% of pregnancies at term. Prematurity is often a factor, with abnormal lie reported to occur in about 2% of pregnancies at 32 weeks’ gestation—six times the rate found at term. Persistence of a transverse, oblique, or unstable lie beyond 37 weeks’ gestation requires a systematic clinical assessment and a plan for management; this is because rupture of the membranes without a fetal part filling the inlet of the pelvis poses an increased risk of cord prolapse, fetal compromise, and maternal morbidity if neglected.
As noted, great parity, prematurity, contraction or deformity of the maternal pelvis, and abnormal placentation are the most commonly reported clinical factors associated with abnormal lie; however, it often happens that none of these factors are present. In fact, any condition that alters the normal vertical polarity of the intrauterine cavity will predispose to abnormal lie.
Diagnosis of the abnormal lie may be made by palpation using Leopold maneuvers or by vaginal examination verified by ultrasound. Whereas routine use of Leopold maneuvers may be helpful, Thorp and colleagues found the sensitivity of Leopold maneuvers for the detection of malpresentation to be only 28%, and the positive predictive value was only 24% compared with immediate ultrasound verification. Others have observed prenatal detection in as few as 41% of cases before labor. Adaptations have been made to the Leopold maneuvers that may improve detection of an abnormal lie or presentation. The Sharma modified Leopold maneuver and the Sharma right and left lateral maneuvers in the original report demonstrated improved diagnostic accuracy; they detected vertex presenting occipitoanterior (95% vs. 84.4%, P = .04), posterior presentations (96.3% vs. 66.6%, P = .00012), and breech presentations correctly more often than with traditional Leopold maneuvers. These maneuvers use the forearms in addition to the hands and fingers. As with any abdominal palpation technique, limitations on accuracy are to be expected in the obese patient and in a patient with uterine myomata. The ready availability of ultrasound in most clinical settings is of benefit, and its use can obviate the vagaries of the abdominal palpation techniques. In all situations, early diagnosis of malpresentation is of benefit . A reported fetal loss rate of 9.2% with an early diagnosis, versus a loss rate of 27.5% with a delayed diagnosis, indicates that early diagnosis improves fetal outcome.
Reported perinatal mortality rates for unstable or transverse lie (corrected for lethal malformations and extreme prematurity) vary from 3.9% to 24%, with maternal mortality as high as 10%. Maternal deaths are usually related to infection after premature rupture of membranes (PROM), hemorrhage secondary to abnormal placentation, complications of operative intervention for cephalopelvic disproportion, or traumatic delivery. Fetal loss of phenotypically and chromosomally normal gestations at ages considered to be viable is primarily associated with delayed interventions, prolapsed cord, or traumatic delivery. Cord prolapse occurs 20 times as often with abnormal lie as it does with a cephalic presentation.
Management of a Singleton Gestation
Safe vaginal delivery of a fetus from an abnormal axial lie is not generally possible. A search for the etiology of the malpresentation is always indicated. A transverse/oblique or unstable lie late in the third trimester necessitates ultrasound examination to exclude a major fetal malformation and abnormal placentation. Fortunately, most cases of major fetal anomalies or abnormal placentation can now be diagnosed long before the third trimester. Phelan and colleagues reported 29 patients with transverse lie diagnosed at or beyond 37 weeks’ gestation and managed expectantly, and 83% (24 of 29) spontaneously converted to breech (9 of 24) or vertex (15 of 24) before labor; however, the overall cesarean delivery rate was 45%, with two cases of cord prolapse, one uterine rupture, and one neonatal death. External cephalic version (ECV) is recommended at 36 to 37 weeks to help diminish the risk of adverse outcome.
In cases of an abnormal lie, the risk of fetal death varies with the obstetric intervention. Fetal mortality should approach zero for cesarean birth but has been reported to be as high as 10% in older reports and between 25% and 90% when IPV and breech extraction are performed. ECV has been found to be safe and relatively efficacious and is further discussed later in this chapter. If external version is unsuccessful or unavailable, if spontaneous rupture of the membranes occurs, or if active labor has begun with an abnormal lie, cesarean delivery is the treatment of choice for the potentially viable infant. There is no place for IPV and breech extraction in the management of transverse or oblique lie or in an unstable presentation in a singleton pregnancy because of the unacceptably high rate of fetal and maternal complications.
A persistent abnormal axial lie, particularly if accompanied by ruptured membranes, also alters the choice of uterine incision at cesarean delivery. A low transverse (Kerr) uterine incision has many surgical advantages and is generally the preferred approach for cesarean delivery for an abnormal lie (see Chapter 19 ). Because up to 25% of transverse incisions may require vertical extension for delivery of an infant from an abnormal lie, and the lower uterine segment is often poorly developed and insufficiently broad such that a traumatic delivery of the presenting part is made more difficult, other uterine incisions may be considered. A “J” or “T” extension of the low transverse incision results in a uterine scar that is more susceptible to subsequent rupture due to poor vascularization. Therefore in the uncommon case of a transverse or oblique lie with a poorly developed lower uterine segment, when a transverse incision is deemed unfeasible or inadequate, a vertical incision (low vertical or classical) may be a reasonable alternative. Intraoperative cephalic version may allow the use of a low transverse incision, but ruptured membranes or oligohydramnios may make this difficult. Uterine relaxing agents such as inhalational anesthetics or intravenous (IV) nitroglycerin may improve success of these maneuvers if the difficulty is attributable to a contracted uterine fundus.
Deflection Attitudes
Attitude refers to the position of the fetal head in relation to the neck. The normal attitude of the fetal head during labor is one of full flexion with the fetal chin against the upper chest. Deflexed attitudes include various degrees of deflection or even extension of the fetal neck and head ( Fig. 17-5 ), leading to, for example, face or brow presentations. Spontaneous conversion to a more normal, flexed attitude or further extension of an intermediate deflection to a fully extended position commonly occurs as labor progresses owing to resistance exerted by the bony pelvis and soft tissues. Although safe vaginal delivery is possible in many cases, experience indicates that cesarean delivery may be the most appropriate alternative when arrest of progress is observed.
Face Presentation
A face presentation is characterized by a longitudinal lie and full extension of the fetal neck and head with the occiput against the upper back ( Fig. 17-6 ). The fetal chin (mentum) is chosen as the point of designation during vaginal examination. For example, a fetus presenting by the face whose chin is in the right posterior quadrant of the maternal pelvis would be called a right mentum posterior ( Fig. 17-7 ). The reported incidence of face presentation ranges from 0.14% to 0.54% and averages about 0.2%, or 1 in 500 live births overall. The reported perinatal mortality rate, corrected for nonviable malformations and extreme prematurity, varies from 0.6% to 5% and averages about 2% to 3%.
All clinical factors known to increase the general rate of malpresentation have been implicated in face presentation; many infants with a face presentation have malformations. Anencephaly, for instance, is found in about one third of cases of face presentation. Fetal goiter and tumors of the soft tissues of the head and neck may also cause deflexion of the head. Frequently observed maternal factors include a contracted pelvis or cephalopelvic disproportion in 10% to 40% of cases. In a review of face presentation, Duff found that one of these etiologic factors was found in up to 90% of cases.
Early recognition of the face presentation is important, and the diagnosis can be suspected when abdominal palpation finds the fetal cephalic prominence on the same side of the maternal abdomen as the fetal back ( Fig. 17-8 ); however, face presentation is more often discovered by vaginal examination. In practice, fewer than 1 in 20 infants with face presentation is diagnosed by abdominal examination. In fact, only half of these infants are found by any means to have a face presentation before the second stage of labor, and half of the remaining cases are undiagnosed until delivery. However, perinatal mortality may be higher with late diagnosis.
Mechanism of Labor
Knowledge of the early mechanism of labor for face presentation is incomplete. Many infants with a face presentation probably begin labor in the less extended brow position. With descent into the pelvis, the forces of labor press the fetus against maternal tissues; subsequent flexion (to a vertex presentation) or full extension of the head on the spine (to a face presentation) then occurs. The labor of a face presentation must include engagement, descent, internal rotation generally to a mentum anterior position, and delivery by flexion as the chin passes under the symphysis ( Fig. 17-9 ). However, flexion of the occiput may not always occur, and delivery in the fully extended attitude may be common.
The prognosis for labor with a face presentation depends on the orientation of the fetal chin. At diagnosis, 60% to 80% of infants with a face presentation are mentum anterior, 10% to 12% are mentum transverse, and 20% to 25% are mentum posterior. Almost all average-sized infants presenting mentum anterior with adequate maternal pelvic dimensions will achieve spontaneous or assisted vaginal delivery. Furthermore, most mentum transverse infants will rotate to the mentum anterior position and will deliver vaginally, and even 25% to 33% of mentum posterior infants will rotate and deliver vaginally in the mentum anterior position. In a review of 51 cases of persistent face presentation, Schwartz and colleagues found that the mean birthweight of those infants in a mentum posterior position who did rotate and deliver vaginally was 3425 g, compared with 3792 g for those infants who did not rotate and deliver vaginally. Persistence of the mentum posterior position with an infant of normal size, however, makes safe vaginal delivery less likely. Overall, 70% to 80% of infants with a face presenting can be delivered vaginally, either spontaneously or by low forceps in the hands of a skilled operator, whereas 12% to 30% require cesarean delivery. Manual attempts to convert the face to a flexed attitude or to rotate a posterior position to a more favorable mentum anterior position are rarely successful and increase both maternal and fetal risks. Again, IPV and breech extraction for face presentation historically are associated with unacceptably high fetal loss rates. Maternal deaths from uterine rupture and trauma have also been documented. Thus contemporary management through spontaneous delivery and cesarean delivery for other obstetric indications as necessary are the preferred routes for both maternal and fetal safety.
Prolonged labor is a common feature of face presentation and has been associated with an increased number of intrapartum deaths; therefore prompt attention to an arrested labor pattern is recommended. In the case of an average or small fetus, an adequate pelvis, and hypotonic labor, oxytocin may be considered. No absolute contraindication to oxytocin augmentation of hypotonic labor in face presentations exists, but an arrest of progress despite adequate labor should call for cesarean delivery.
Worsening of the fetal condition in labor is common. Salzmann and colleagues observed a tenfold increase in fetal compromise with face presentation. Several other observers have also found that abnormal fetal heart rate (FHR) patterns occur more often with face presentation. Continuous intrapartum electronic FHR monitoring of a fetus with face presentation is considered mandatory, but extreme care must be exercised in the placement of an electrode because ocular or cosmetic damage is possible. If external Doppler heart rate monitoring is inadequate and an internal electrode is recommended, placement of the electrode on the fetal chin is often preferred.
Contraindications to vaginal delivery of a face presentation include macrosomia, nonreassurance of FHR monitoring even without arrested or protracted labor, or an inadequate maternal pelvis; cesarean delivery has been reported in as many as 60% of cases of face presentation for these reasons. If cesarean delivery is warranted, care should be taken to flex the head gently, both to accomplish elevation of the head through the hysterotomy incision as well as to avoid potential cervical nerve damage to the neonate. Forced flexion may also result in fetal injury, especially with fetal goiter or neck tumors.
Fetal laryngeal and tracheal edema that results from the pressure of the birth process might require immediate nasotracheal intubation. Nuchal tumors or simple goiters, fetal anomalies that might have caused the malpresentation, require expert neonatal management, including the possibility of an ex utero intrapartum treatment (EXIT) procedure, which establishes a fetal/neonatal airway before the umbilical cord is clamped. Identification of and planning for these particular circumstances in the prelabor setting are ideal.
Brow Presentation
A fetus in a brow presentation occupies a longitudinal axis with a partially deflexed cephalic attitude midway between full flexion and full extension ( Fig. 17-10 ). The frontal bones are the point of designation. If the anterior fontanel is on the mother’s left side, with the sagittal suture in the transverse pelvic axis, the fetus would be in a left frontum transverse position ( Fig. 17-11 ). The reported incidence of brow presentation varies widely, from 1 in 670 to 1 in 3433, averaging about 1 in 1500 deliveries. Brow presentation is detected more often in early labor before flexion occurs to a normal attitude. Less frequently, further extension results in a face presentation.
In 1976, the perinatal mortality rate corrected for lethal anomalies and very low birthweight varied from 1% to 8%. In a study of 88,988 deliveries, corrected perinatal mortality rates for brow presentations depended on the mode of delivery; a loss rate of 16%, the highest in this study, was associated with manipulative vaginal birth.
In general, factors that delay engagement are associated with persistent brow presentation. Cephalopelvic disproportion, prematurity, and high parity are often found and have been implicated in more than 60% of cases of persistent brow presentation.
Detection of a brow presentation by abdominal palpation is unusual in practice. More often, a brow presentation is detected on vaginal examination. As in the case of a face presentation, diagnosis in labor is more likely. Fewer than 50% of brow presentations are detected before the second stage of labor, and most of the remainder are undiagnosed until delivery. Frontum anterior is reportedly the most common position at diagnosis, occurring about twice as often as either transverse or posterior positions. Although the initial position at diagnosis may be of limited prognostic value, the cesarean delivery rate is higher with frontum transverse or frontum posterior than with frontum anterior positioning.
A persistent brow presentation requires engagement and descent of the largest (mento-occipital) diameter of the fetal head. This process is possible only with a large pelvis or a small infant, or both. However, most brow presentations convert spontaneously by flexion or further extension to either a vertex or a face presentation and are then managed accordingly. The earlier the diagnosis is made, the more likely conversion will occur spontaneously. Fewer than half of fetuses with persistent brow presentations undergo spontaneous vaginal delivery, but in most cases, a trial of labor is not contraindicated.
Prolonged labors have been observed in 33% to 50% of brow presentations, and secondary arrest is not uncommon. Forced conversion of the brow to a more favorable position with forceps is contraindicated, as are attempts at manual conversion. One unexpected cause of persistent brow presentation may be an open fetal mouth pressed against the vaginal wall, splinting the head and preventing either flexion or extension ( Fig. 17-12 ). Although this is rare in phenotypically normal fetuses, it needs to be considered in anomalous conditions of the fetus such as epignathus, a rare oropharyngeal teratoma.
Similar to face presentations, minimal manipulation yields the best results if the FHR pattern remains reassuring. Expectant management may be justified, preferably with a relatively large pelvis in relation to fetal size and adequate labor progress, according to one large study. If a brow presentation persists with a large baby, successful vaginal delivery is unlikely, and cesarean delivery may be most prudent.
Radiographic or computed tomographic (CT) pelvimetry is not used clinically, and one report states that although 91% of cases with adequate pelvimetry converted to a vertex or a face presentation and delivered vaginally, 20% with some form of pelvic contracture did also. Therefore regardless of pelvic dimensions, consideration of a trial of labor with careful monitoring of maternal and fetal condition may be appropriate. As in the case of a face presentation, oxytocin may be used cautiously to correct hypotonic contractions, but prompt resumption of progress toward delivery should follow.
Compound Presentation
Whenever an extremity, most commonly an upper extremity, is found prolapsed beside the main presenting fetal part, the situation is referred to as a compound presentation ( Fig. 17-13 ). The reported incidence ranges from 1 in 377 to 1 in 1213 deliveries. The combination of an upper extremity and the vertex is the most common.
This diagnosis should be suspected with any arrest of labor in the active phase or failure to engage during active labor. Diagnosis is made on vaginal examination by discovery of an irregular mobile tissue mass adjacent to the larger presenting part. Recognition late in labor is common, and as many as 50% of persisting compound presentations are not detected until the second stage. Delay in diagnosis may not be detrimental because it is likely that only the persistent cases require intervention.
Although maternal age, race, parity, and pelvic size have been associated with compound presentation, prematurity is the most consistent clinical finding. The very small premature fetus is at great risk of persistent compound presentation. In late pregnancy, ECV of a fetus in breech position increases the risk of a compound presentation.
Older, uncontrolled studies report elevated perinatal mortality rates with a compound presentation, with an overall rate of 93 per 1000. Higher loss rates of 17% to 19% have been reported when the foot prolapses. As with other malpresentations, fetal risk is directly related to the method of management. A fetal mortality rate of 4.8% has been noted if no intervention is required compared with 14.4% with intervention other than cesarean delivery. A 30% fetal mortality rate has been observed with IPV and breech extraction. These figures may demonstrate selection bias because it is possible that more often, the difficult cases were chosen for manipulative intervention. When intervention is necessary, cesarean delivery appears to be the only safe choice.
Fetal risk in compound presentation is specifically associated with birth trauma and cord prolapse. Cord prolapse occurs in 11% to 20% of cases, and it is the most frequent complication of this malpresentation. Cord prolapse probably occurs because the compound extremity splints the larger presenting part and results in an irregular fetal aggregate that incompletely fills the pelvic inlet. In addition to the hypoxic risk of cord prolapse, common fetal morbidity includes neurologic and musculoskeletal damage to the involved extremity. Maternal risks include soft tissue damage and obstetric laceration. Again, although laboring is not proscribed, the prolapsed extremity should not be manipulated. However, it may spontaneously retract as the major presenting part descends. Seventy-five percent of vertex/upper extremity combinations deliver spontaneously. Occult or obscured cord prolapse is possible, and therefore continuous electronic FHR monitoring is recommended.
The primary indications for surgical intervention (i.e., cesarean delivery) are cord prolapse, nonreassuring FHR patterns, and arrest of labor. Cesarean delivery is the only appropriate clinical intervention for cord prolapse and nonreassuring FHR patterns because both version extraction and repositioning the prolapsed extremity are associated with adverse outcome and should be avoided. From 2% to 25% of compound presentations require cesarean delivery. Protraction of the second stage of labor and dysfunctional labor patterns have been noted to occur more frequently with persistent compound presentations. As in other malpresentations, spontaneous resolution occurs more often, and surgical intervention is less frequently necessary in those cases diagnosed early in labor. Small or premature fetuses are more likely to have persistent compound presentations but are also more likely to have a successful vaginal delivery. Persistent compound presentation with parts other than the vertex and hand in combination in a term-sized infant has a poor prognosis for safe vaginal delivery, and cesarean delivery is usually necessary. However, a simple compound presentation (e.g., hand) may be allowed to labor, if labor is progressing normally with reassuring fetal status.
Breech Presentation
The infant presenting as a breech occupies a longitudinal axis with the cephalic pole in the uterine fundus. This presentation occurs in 3% to 4% of labors overall, although it is found in 7% of pregnancies at 32 weeks and in 25% of pregnancies of less than 28 weeks’ duration. The three types of breech are noted in Table 17-1 . The infant in the frank breech position is flexed at the hips with extended knees (pike position). The complete breech is flexed at both joints (tuck position), and the footling or incomplete breech has one or both hips partially or fully extended ( Fig. 17-14 ).
| TYPE | OVERALL % OF BREECHES | RISK OF PROLAPSE (%) † | PREMATURE (%) ‡ |
|---|---|---|---|
| Frank | 48-73 * † ‡ | 0.5 | 38 |
| Complete | 4.6-11.5 † ‡ | 4-6 | 12 |
| Footling | 12-38 ‡ | 15-18 | 50 |
* Data from Collea JV, Chein C, Quilligan EJ. The randomized management of term frank breech presentation: a study of 208 cases. Am J Obstet Gynecol. 1980;137:235-244.
† Data from Gimovsky ML, Wallace RL, Schifrin BS, Paul RH. Randomized management of the nonfrank breech presentation at term: a preliminary report. Am J Obstet Gynecol. 1983;146:34-40.
‡ Data from Brown L, Karrison T, Cibils LA. Mode of delivery and perinatal results in breech presentation. Am J Obstet Gynecol. 1994;171:28-34.
The diagnosis of breech presentation may be made by abdominal palpation or vaginal examination and confirmed by ultrasound. Prematurity, fetal malformation, müllerian anomalies, and polar placentation are commonly observed causative factors. High rates of breech presentation are noted in certain fetal genetic disorders, including trisomies 13, 18, and 21; Potter syndrome; and myotonic dystrophy. Conditions that alter fetal muscular tone and mobility—such as increased and decreased amniotic fluid, for example—also increase the frequency of breech presentation. The breech head appears dolichocephalic on ultrasound, and for that reason, the biparietal diameter (BPD) appears small. However, the head circumference remains unaffected. This difference may be as much as 16+ days (95% confidence interval [CI], 14.3 to 18.1; P = .001). Whereas the contracted BPD may affect ultrasound-determined weight estimates of the fetus, an occipitofrontal diameter (OFD) to BPD ratio of greater than 1.3 in the absence of other indicators of growth delay signals the deformation characteristic of the breech-presenting fetus. Approximately 80% of breech fetuses will have a dolichocephalic contour, previously termed the “breech head.” The fundus of the uterus assumes a more elongated contour than the bowl-like developed lower uterine segment. Thus it is believed that forces external to the fetus are responsible for this head shape. Because both dolichocephaly and breech may be associated with a genetically and phenotypically anomalous fetus, it behooves the sonologist to perform a detailed survey of the fetal anatomy prior to assuming the presence of the “breech head.”
Mechanism and Conduct of Labor and Vaginal Delivery
The two most important elements for the safe conduct of vaginal breech delivery are continuous electronic FHR monitoring and noninterference until spontaneous delivery of the breech to the umbilicus has occurred. Early in labor, the capability for immediate cesarean delivery should be established. Anesthesia should be available, the operating room readied, and appropriate informed consent obtained (discussed later). Two obstetricians should be in attendance in addition to a pediatric team. Appropriate training and experience with vaginal breech delivery are fundamental to success. Although experience is becoming infinitely less common, simulation of breech deliveries will help to maintain these skills. The instrument table should be prepared in the customary manner, with the addition of Piper forceps and extra towels. No contraindication exists to epidural analgesia in labor, and many believe epidural anesthesia to be an asset in the control and conduct of the second stage.
The infant presenting in the frank breech position usually enters the pelvic inlet in one of the diagonal pelvic diameters ( Fig. 17-15 ). Engagement has occurred when the bitrochanteric diameter of the fetus has progressed beyond the plane of the pelvic inlet, although by vaginal examination, the presenting part may be palpated only at a station of −2 to −4 (out of 5). As the breech descends and encounters the levator ani muscular sling, internal rotation usually occurs to bring the bitrochanteric diameter into the anteroposterior (AP) axis of the pelvis. The point of designation in a breech labor is the fetal sacrum ; therefore when the bitrochanteric diameter is in the AP axis of the pelvis, the fetal sacrum will lie in the transverse pelvic diameter ( Fig. 17-16 ).
If normal descent occurs, the breech will present at the outlet and will begin to emerge, first as sacrum transverse, then rotating to sacrum anterior. This direction of rotation may reflect the greater capacity of the hollow of the posterior pelvis to accept the fetal chest and small parts. Crowning occurs when the bitrochanteric diameter passes under the pubic symphysis. It is important to emphasize that operator intervention is not yet needed or helpful, other than possibly to perform the episiotomy if indicated and to encourage maternal expulsive efforts.
Premature or aggressive intervention may adversely affect the delivery in at least two ways. First, complete cervical dilation must be sustained for sufficient duration to retard retraction of the cervix and entrapment of the aftercoming fetal head. Rushing the delivery of the trunk may result in cervical retraction. Second, the safe descent and delivery of the breech infant must be the result of uterine and maternal expulsive forces only in order to maintain neck flexion. Any traction by the provider in an effort to speed delivery would encourage deflexion of the neck and result in the presentation of the larger occipitofrontal fetal cranial profile to the pelvic inlet ( Fig. 17-17 ). Such an event could be catastrophic. Rushed delivery also increases the risk of a nuchal arm, with one or both arms trapped behind the head above the pelvic inlet. Entrapment of a nuchal arm makes safe vaginal delivery much more difficult because it dramatically increases the aggregate size of delivering fetal parts that must egress vaginally. Safe breech delivery of an average-sized infant, therefore, depends predominantly on maternal expulsive forces and patience, not traction, from the provider.
As the frank breech emerges further, the fetal thighs are typically flexed firmly against the fetal abdomen, often splinting and protecting the umbilicus and cord. The Pinard maneuver may be needed to facilitate delivery of the legs in a frank breech presentation. After delivery to the umbilicus has occurred, pressure is applied to the medial aspect of the knee, which causes flexion and subsequent delivery of the lower leg. Simultaneous to this, the fetal pelvis is rotated away from that side ( Fig. 17-18 ). This results in external rotation of the thigh at the hip, flexion of the knee, and delivery of one leg at a time. The dual movement of counterclockwise rotation of the fetal pelvis as the operator externally rotates the right thigh and clockwise rotation of the fetal pelvis as the operator externally rotates the fetal left thigh is most effective in facilitating delivery. The fetal trunk is then wrapped with a towel to provide secure support of the body while further descent results from expulsive forces from the mother. The operator primarily facilitates the delivery of the fetus by providing support and guiding the body through the introitus. The operator is not applying outward traction on the fetus, which might result in deflexion of the fetal head or nuchal arm.
When the scapulae appear at the introitus, the operator may slip a hand over the fetal shoulder from the back ( Fig. 17-19 ); follow the humerus; and, with movement from medial to lateral, sweep first one and then the other arm across the chest and out over the perineum. Gentle rotation of the fetal trunk counterclockwise assists delivery of the right arm, and clockwise rotation assists delivery of the left arm (turning the body “into” the arm). This accomplishes delivery of the arms by drawing them across the fetal chest in a fashion similar to that used for delivery of the legs ( Fig. 17-20 ). These movements cause the fetal elbow to emerge first, followed by the forearm and hand. Once both arms have been delivered, if the vertex has remained flexed on the neck, the chin and face will appear at the outlet, and the airway may be cleared and suctioned ( Fig. 17-21 ).
With further maternal expulsive forces alone, spontaneous controlled delivery of the fetal head often occurs. If not, delivery may be accomplished with a simple manual effort to maximize flexion of the vertex using pressure on the fetal maxilla (not the mandible), the Mauriceau-Smellie-Veit maneuver, using gentle downward traction along with suprapubic pressure (Credé maneuver; Fig. 17-22 ). Although maxillary pressure facilitates flexion, the main force effecting delivery remains the mother.
Alternatively, the operator may apply Piper forceps to the aftercoming head. The application requires very slight elevation of the fetal trunk by the assistant, while the operator kneels and applies the Piper forceps from beneath the fetus directly to the fetal head in the pelvis. Delivery of the breech presenting fetus, therefore, should occur on a table/bed capable of allowing the operators to correctly position themselves for the application of forceps. Direct access to the perineum is required. If a delivery bed is used, merely dropping the foot of the bed will be inadequate. The position of the operator for applying the forceps is depicted in Figure 17-23 , which also demonstrates how excessive elevation by the assistant may potentially cause harm to the neonate. Hyperextension of the fetal neck from excessive elevation of the fetal trunk, shown in Figure 17-23 , should be avoided because of the potential for spinal cord injury.
Piper forceps are characterized by absence of pelvic curvature. This modification allows direct application to the fetal head and avoids conflict with the fetal body that would occur with the application of standard instruments from below. The assistant maintains control of the fetal body while the forceps are inserted into the vagina from beneath the fetus by the primary operator. The blade to be placed on the maternal left is held by the handle in the operator’s left hand; the blade is inserted with the operator’s right hand in the vagina along the left maternal sidewall and is placed against the right fetal parietal bone. The handle of the right blade is then held in the operator’s right hand and is inserted by the left hand along the right maternal sidewall and placed against the left fetal parietal bone. At this point, the assistant allows the fetal body to rest on the shank and handles of the forceps. Gentle downward traction on the forceps with the fetal trunk supported on the forceps shanks results in controlled delivery of the vertex ( Fig. 17-24 ). Forceps application controls the fetal head and prevents extension of the head on the neck. Application of Piper forceps to the aftercoming head may be advisable both to ensure control of the delivery and to maintain optimal operator proficiency in anticipation of deliveries that may require their use.
Arrest of spontaneous progress in labor with adequate uterine contractions necessitates consideration of cesarean delivery. Any evidence of fetal compromise or sustained cord compression on the basis of continuous electronic FHR monitoring also requires consideration of cesarean delivery. Vaginal interventions directed at facilitating delivery of the breech complicated by an arrest of spontaneous progress are discouraged because fetal and maternal morbidity and mortality are both greatly increased. However, if labor is deemed to be hypotonic by internally monitored uterine pressures, oxytocin is not contraindicated.
Mechanisms of descent and delivery of the incomplete and the complete breech are not unlike those used for the frank breech described earlier; at least one leg may not require attention. The risk of cord prolapse or entanglement is greater, and hence the possibility of emergency cesarean delivery is increased. Furthermore, incomplete and complete breeches may not be as effective as cervical dilators as either the vertex or the larger aggregate profile of the thighs and buttocks of the frank breech. Thus the risk of entrapment of the aftercoming head is increased, and as a result, primary cesarean delivery is often advocated for nonfrank breech presentations. However, the randomized trial of Gimovsky and colleagues found vaginal delivery of the nonfrank breech to be reasonably safe.
Contemporary Management of the Term Breech
Debate has largely diminished about the proper management of the term breech. Much of the older data were derived from relatively few studies of varied methodologies, patient populations, and multiple retrospective cohort analyses, which are subject to bias. These reports indicated that the perinatal mortality rate for the vaginally delivered breech appears to be greater than for its cephalic counterpart, but much of the reported perinatal mortality rate associated with breech presentation was largely due to lethal anomalies and complications of prematurity, both of which are found more frequently among breech infants. Excluding anomalies and extreme prematurity, the corrected perinatal mortality reported by some investigators approached zero regardless of the method of delivery, whereas others found that even with exclusion of these factors, the term breech infant has been found to be at higher risk for birth trauma and asphyxia. To date, only three randomized trials have been reported. Although conclusions regarding the safety of breech vaginal delivery from a fetal standpoint may continue to vary, the practical reality today is that intentional vaginal breech delivery is rare. A summary of some of the reported complications is listed in Table 17-2 . Overall, consideration of a potential breech vaginal delivery must be mutually agreed on by the patient and the physician after complete informed consent is obtained.
