Chapter 19. Malpresentation & Cord Prolapse

Essentials of Diagnosis

• Breech presentation occurs when the fetal pelvis or lower extremities engage the maternal pelvic inlet.
• Breech presentation may be suspected based on clinical examination, either by palpating fetal parts over the maternal abdomen or by pelvic examination.
• The diagnosis can be confirmed via ultrasound.

Breech presentation, which complicates 3–4% of all pregnancies, occurs when the fetal pelvis or lower extremities engage the maternal pelvic inlet. Three types of breech are distinguished, according to fetal attitude (Fig. 19–1). In frank breech, the hips are flexed with extended knees bilaterally. In complete breech, both hips and knees are flexed. In footling breech, 1 (single footling breech) or both (double footling breech) legs are extended below the level of the buttocks.

In singleton breech presentations in which the infant weighs less than 2500 g, 40% are frank breech, 10% complete breech, and 50% footling breech. With birth weights of more than 2500 g, 65% are frank breech, 10% complete breech, and 25% footling breech. The incidences of singleton breech presentations by birth weight and gestational age are listed in Table 19–1.

Fetal position in breech presentation is determined by using the fetal sacrum as the point of reference to the maternal pelvis. This is true for frank, complete, and footling breeches. Eight possible positions are recognized: sacrum anterior (SA), sacrum posterior (SP), left sacrum transverse (LST), right sacrum transverse (RST), left sacrum anterior (LSA), left sacrum posterior (LSP), right sacrum anterior (RSA), and right sacrum posterior (RSP). The station of the breech presenting part is the location of the fetal sacrum with regard to the maternal ischial spines.

Pathogenesis

Before 28 weeks, the fetus is small enough in relation to intrauterine volume to rotate from cephalic to breech presentation and back again with relative ease. As gestational age and fetal weight increase, the relative decrease in intrauterine volume makes such changes more difficult. In most cases, the fetus spontaneously assumes the cephalic presentation to better accommodate the bulkier breech pole in the roomier fundal portion of the uterus.

Breech presentation occurs when spontaneous version to cephalic presentation is prevented as term approaches or if labor and delivery occur prematurely before cephalic version has taken place. Some causes include oligohydramnios, polyhydramnios, uterine anomalies such as bicornuate or septate uterus, pelvic tumors obstructing the birth canal, abnormal placentation, advanced multiparity, and a contracted maternal pelvis.

In multiple gestations, each fetus may prevent the other from turning, with a 25% incidence of breech in the first twin, nearly 50% for the second twin, and higher percentages with additional fetuses. Additionally, 6% of breech presentations are found to have congenital malformations, which include congenital hip dislocation, hydrocephalus, anencephalus, familial dysautonomia, spina bifida, meningomyelocele, and chromosomal trisomies 13, 18, and 21. Thus, those conditions that alter fetal muscular tone and mobility increase the likelihood of breech presentation.

Clinical Findings

Palpation & Ballottement

Performance of Leopold's maneuvers and manual ballottement of the uterus through the maternal abdominal wall may confirm breech presentation. The softer, more ill-defined breech may be felt in the lower uterine segment above the pelvic inlet. Diagnostic error is common, however, if these maneuvers alone are used to determine presentation.

Pelvic Examination

During vaginal examination, the round, firm, smooth head in cephalic presentation can easily be distinguished from the soft, irregular breech presentation if the presenting part is palpable. However, if no presenting part is discernible, further studies are necessary (ie, ultrasound).

Radiographic Studies

X-ray studies will differentiate breech from cephalic presentations and help determine the type of breech by locating the position of the lower extremities. X-ray studies can reveal multiple gestation and skeletal defects. Fetal attitude may be seen, but fetal size cannot readily be determined by x-ray film. Because of the risks of radiation exposure to the fetus with this technique, ultrasonography is now used instead of radiography to determine fetal presentation or malformations.

Ultrasound

Ultrasonographic scanning by an experienced examiner will document fetal presentation, attitude, and size; multiple gestation; location of the placenta; and amniotic fluid volume. Ultrasound also will reveal skeletal and soft tissue malformations of the fetus.

Complications

Birth Anoxia

Umbilical cord compression and prolapse may be associated with breech delivery, particularly in complete (5%) and footling (15%) presentations. This is due to the inability of the presenting part to fill the maternal pelvis, either because of prematurity or poor application of the presenting part to the cervix so that the umbilical cord is allowed to prolapse below the level of the breech (see below). Frank breech presentation offers a contoured presenting part, which is better accommodated to the maternal pelvis and is usually well applied to the cervix. The incidence of cord prolapse in frank breech is only 0.5% (the same as for cephalic presentations). Compression of the prolapsed cord may occur during uterine contractions, causing moderate to severe variable decelerations in the fetal heart rate and leading to fetal anoxia or death. If breech vaginal delivery is attempted, continuous electronic monitoring is mandatory during labor in these cases to detect ominous decelerations. If they occur, immediate caesarean delivery must be performed.

Birth Injury

The incidence of birth trauma during vaginal breech delivery is 6.7%, 13 times that of cephalic presentations (0.51%). Only high forceps and internal version and extraction procedures have higher rates of birth injury than do vaginal breech deliveries. The types of perinatal injuries reported in breech delivery include tears in the tentorium cerebellum, cephalohematomas, disruption of the spinal cord, brachial palsy, fracture of long bones, and rupture of the sternocleidomastoid muscles. Vaginal breech delivery is the main cause of injuries to the fetal adrenal glands, liver, anus, genitalia, spine, hip joint, sciatic nerve, and musculature of the arms, legs, and back.

Factors contributing to difficult vaginal breech delivery include a partially dilated cervix, unilateral or bilateral nuchal arms, and deflexion of the head. The type of procedure used may affect the neonatal outcome.

Partially Dilated Cervix

Delivery of a breech fetus may progress even though the cervix is only partially dilated because the bitrochanteric and bisacromial diameters are smaller than the biparietal diameter. This is true especially in prematurity. The hips and shoulders may negotiate the cervix, but the aftercoming head becomes entrapped, resulting in difficult delivery and birth injury.

Nuchal Arms

During partial breech extraction and more often in total breech extraction, excessive downward traction on the body results in a single or double nuchal arm. This occurs because of the rapid descent of the body, leading to extension of 1 or both arms, which become lodged behind the neck. When delivery of the shoulder is difficult to accomplish, a nuchal arm should be suspected. To dislodge the arm, the operator rotates the body 180 degrees to bring the elbow toward the face. The humerus can then be identified and delivered by gentle downward traction. In cases of double nuchal arm, the fetus is rotated counterclockwise to dislodge and deliver the right arm and rotated clockwise to deliver the left arm. If this action is unsuccessful, the operator must insert a finger into the pelvis, identify the humerus, and possibly extract the arm, resulting in fracture of the humerus or clavicle. Nuchal arms cause a delay in delivery and increase the incidence of birth asphyxia.

Deflexion of the Head

Hyperextension of the head is defined as deflexion or extension of the head posteriorly beyond the longitudinal axis of the fetus (5% of all breech deliveries). Causes of hyperextension include neck cysts, spasm of the neck musculature, and uterine anomalies, but over 75% have no known cause. Although deflexion may be documented by ultrasonographic or x-ray studies weeks before delivery, there is little apparent risk to the fetus until vaginal delivery is attempted. At that time, deflexion causes impaction of the occipital portion of the head behind the pubic symphysis, which may lead to fractures of the cervical vertebrae, lacerations of the spinal cord, epidural and medullary hemorrhages, and perinatal death. If head deflexion is diagnosed prior to delivery, caesarean section should be performed to avert injury. Caesarean section cannot prevent injuries such as minor meningeal hemorrhage or dislocation of the cervical vertebrae, which may develop in utero secondary to longstanding head deflexion.

Type of Delivery

More complex delivery procedures have a higher rate of birth trauma. Whereas few infants are injured during spontaneous breech births, as many as 6% are injured during partial breech extraction and 20% during total breech extraction of singleton infants. Injuries associated with total breech extraction of singleton infants usually are extensive and severe, and this procedure should never be attempted unless fetal survival is in jeopardy and caesarean section cannot be immediately performed.

An additional important factor in breech injury and perinatal outcome is the experience of the operator. Inexperience may lead to hasty performance of obstetric maneuvers. Delay in delivery may result in birth asphyxia due to umbilical cord compression, but haste in the management of breech delivery results in application of excessive pressure on the fetal body, causing soft tissue damage and fracture of long bones. Too-rapid extraction of the body from the birth canal causes the arms to extend above the head, resulting in unilateral or bilateral nuchal arms and difficult delivery of the aftercoming head. All breech deliveries should be performed slowly and methodically by experienced obstetricians who execute the maneuvers with gentleness and skill—not speed.

Treatment

Antepartum Management

Following confirmation of breech presentation, the mother must be closely followed to evaluate for spontaneous version to cephalic presentation. If breech presentation persists beyond 36 weeks, external cephalic version should be considered (see below). Version is a procedure used to turn the fetal presenting part from breech to cephalic presentation (cephalic version) or from cephalic to breech presentation (podalic version). Because cephalic version is performed by manipulating the fetus through the abdominal wall, the maneuver is known as external cephalic version. Podalic version is performed by means of internal maneuvers and is known as internal podalic version (see below). External cephalic version is regaining popularity, whereas internal podalic version is rarely used.

In women considering a vaginal breech delivery of a singleton infant, radiographic pelvimetry using x-ray, computed tomography, or magnetic resonance imaging should be performed to rule out women with a borderline or contracted pelvis. Attempts at vaginal delivery with an inadequate pelvis are associated with a high rate of difficulty and significant trauma to mother and fetus. Difficult vaginal delivery may still occur in women with adequate pelvic measurements.

External cephalic version is used in the management of singleton breech presentations or in a nonvertex second twin. In carefully selected patients, it is safe for both mother and fetus. The goal is to increase the proportion of vertex presentations near term, thus increasing the chance for a vaginal delivery. In the past, external cephalic version was performed earlier in gestation but was accompanied by high reversion rates, making additional procedures necessary. Now it is performed in patients who have completed 36 weeks of gestation so that the risk of spontaneous reversion is decreased, and, if complications arise, delivery of a term infant can be accomplished. Current success rates for external cephalic version range from 35 to 85% (mean 60%).

Patients with unengaged singleton breech presentations of at least 36 weeks' gestation are candidates for external cephalic version. The procedure is more successful in multigravidas, those with a transverse or oblique lie, and those with a posterior placenta. Use of fetal heart rate monitoring and real-time ultrasonography is essential to document fetal well-being during the procedure. The use of tocolytics in external cephalic version is controversial. Recent evidence indicates that tocolytics offer an advantage in nulliparous women, but reports on which type of tocolytic confers the highest success rate are conflicting. Thus, these agents should be used at the discretion of the physician. Additionally, evidence regarding the use of regional anesthesia is inconsistent. Recent randomized controlled trials have shown an increased success rate in those with epidural anesthesia. However, the ultimate decision should be based on physician experience.

Contraindications to external cephalic version include engagement of the presenting part in the pelvis, marked oligohydramnios, placenta previa, uterine anomalies, presence of nuchal cord, multiple gestation, premature rupture of membranes, previous uterine surgery (including myomectomy or metroplasty), and suspected or documented congenital malformations or abnormalities (including intrauterine growth retardation).

Complications are rare, occurring in only 1–2% of all external cephalic versions. Complications include placental abruption, uterine rupture, rupture of membranes with resultant umbilical cord prolapse, amniotic fluid embolism, preterm labor, fetal distress, fetomaternal hemorrhage, and fetal demise. Thus, given the potential for catastrophic outcome, this procedure should be performed in a facility where immediate access to caesarean delivery is available. Patients require extensive counseling regarding the version procedure, with disclosure of all risks, benefits, and alternatives so that an informed medicolegal decision can be made.

Fetal Heart Rate Abnormalities

These can be readily documented during external cephalic version by intermittent electronic fetal monitoring (EFM) or ultrasonographic surveillance. Fetal bradycardia occurs in 20% of cases, but normal cardiac activity usually will return if the procedure is stopped for a short time. If significant unremitting fetal cardiac alterations occur, the attempt at version should be discontinued and preparation for caesarean delivery undertaken immediately.

Fetomaternal Transplacental Hemorrhage (Fmh)

This may occur during version and has been reported to occur in 6–28% of patients undergoing external cephalic version, although the amount of hemorrhage rarely results in clinically significant anemia. The Kleihauer-Betke acid elution test should be performed if this condition is suspected. In cases of an Rh-negative–unsensitized woman, Rh immune globulin (RhoGAM) should be administered after external cephalic version to cover the calculated amount of FMH.

Technique

External cephalic version is performed by first obtaining informed consent from the patient. An ultrasound examination is performed to verify presentation and to rule out fetal or uterine abnormalities. A nonstress test is done, and results must be reactive. If desired, a tocolytic is administered to prevent contractions or irritability. Anesthesia is also administered if desired. To perform the external cephalic version, both of the operator's hands are placed on the patient's abdomen, and a forward roll is attempted by lifting the breech upward while placing pressure on the head downward toward the pelvis. If this maneuver is unsuccessful, a backward roll can be attempted. Fetal well-being should be monitored intermittently with Doppler or real-time ultrasound scanning. The procedure should be abandoned in case of any significant fetal distress or patient discomfort or if multiple attempts are unsuccessful. Following the procedure, external fetal heart rate monitoring should be continued for 1 hour to ensure stability. If the patient is Rh negative, administer anti-D immune globulin. If the patient is stable, she can be sent home to await the onset of spontaneous labor if the version is successful. If unsuccessful, the patient can be scheduled for an elective caesarean section or a trial of labor with a breech vaginal delivery planned if the mother is a good candidate.

Recent studies have evaluated acupuncture and moxibustion (burning herbs to stimulate acupuncture points) to determine their role in facilitating spontaneous version of the breech fetus. To date, these trials have not found a consistent benefit to either mode.

Management during Labor

Examination

Patients with singleton breech presentations are admitted to the hospital with the onset of labor or when spontaneous rupture of membranes occurs because of the increased risk of umbilical cord complications. Upon admission, a repeat ultrasound is obtained to confirm the type of breech presentation and to ascertain head flexion. The fetus is again screened for lethal congenital malformations, such as anencephaly, which would preclude caesarean delivery for fetal indications. A thorough history is taken, and a physical examination is performed to evaluate the status of mother and fetus. Based on these findings, a decision must be made regarding the route of delivery (see below).

Electronic Fetal Monitoring

Continuous electronic fetal heart rate monitoring is essential during labor. If a fetal electrocardiographic electrode is needed, care should be taken to avoid injury to the fetal anus, perineum, and genitalia when attaching the electrode to the breech presenting part. An intrauterine pressure catheter can be used to assess the frequency, strength, and duration of uterine contractions. With the catheter in place, fetal distress or dysfunctional labor can easily be identified and the decision to proceed with a caesarean section made expeditiously to optimize fetal outcome.

Oxytocin

The use of oxytocin in the management of breech labor is controversial. Although some obstetricians condemn its use, others use oxytocin with benefit and without complications. Generally, oxytocin should be administered only if uterine contractions are insufficient to sustain normal progress in labor. Continuous fetal and uterine monitoring should be used whenever oxytocin is administered.

Delivery

The decision regarding route of delivery must be made carefully on an individual basis. Criteria for vaginal or caesarean delivery are outlined in Table 19–2.

Prior to 1975, virtually all viable singleton breech presentations were delivered vaginally. Caesarean section was reserved for specific fetal indications, such as unremitting distress or prolapsed umbilical cord, or maternal indications, such as placenta previa, abruptio placentae, or failure of progress in labor. However, breech infants delivered vaginally had a 5-fold higher mortality rate in comparison to cephalic presentations.

Recent studies have shown that planned caesarean delivery decreases perinatal and neonatal morbidity and mortality, with no difference in maternal morbidity and mortality versus planned vaginal breech delivery. Thus, caesarean delivery has now become much more common in breech presentation. Only obstetricians skilled in breech techniques should attempt any breech delivery, whether vaginal or caesarean. Nevertheless, broader familiarity with the technique is needed because unanticipated vaginal breech delivery is still encountered.

Caesarean Delivery

The type of incision chosen is extremely important. If the lower uterine segment is well developed, as is usually the case in women at term in labor, a transverse “lower segment” incision is adequate for easy delivery. In premature gestations, in an unlabored uterus, or in many cases of malpresentation, the lower uterine segment may be quite narrow, and a low vertical incision is almost always required for atraumatic delivery.

Vaginal Delivery

Obstetricians who contemplate performing a vaginal breech delivery should be experienced in the maneuver and should be assisted by 3 physicians: (1) an experienced obstetrician who will assist with delivery; (2) a pediatrician capable of providing total resuscitation of the newborn; and (3) an anesthesiologist, to ensure that the mother is comfortable and cooperative during labor and delivery. The type of anesthesia required depends on the type of breech delivery. Multiparous women undergoing spontaneous breech delivery may require no anesthesia or only intravenous analgesia for pain relief during labor and a pudendal anesthetic during delivery. Epidural anesthesia may also be administered during labor or in anticipation of partial breech extraction, including application of Piper forceps to the aftercoming head. In emergency circumstances, complete relaxation of the perineum and uterus is essential for a successful outcome. This is accomplished by immediate induction of inhalation anesthesia or by administration of intravenous nitroglycerin.

a. Spontaneous Vaginal Delivery—

During spontaneous delivery of an infant in the frank breech position, delivery occurs without assistance, and no obstetric maneuvers are applied to the body. The fetus negotiates the maternal pelvis as outlined below, while the operator simply supports the body as it delivers.

Engagement occurs when the bitrochanteric diameter of the fetus has passed the plane of the pelvic inlet. As the fetus descends into the pelvis (Fig. 19–2), the buttocks reach the levator ani muscles of the maternal pelvis. At this point, internal rotation occurs, whereby the anterior hip rotates beneath the pubic symphysis, resulting in a sacrum transverse position. The bitrochanteric diameter of the fetal pelvis is now in an anteroposterior position within the maternal pelvis. The breech then presents at the pelvic outlet and, upon emerging, rotates from sacrum transverse to sacrum anterior. Crowning occurs when the bitrochanteric diameter passes under the pubic symphysis. As this occurs, the shoulders enter the pelvic inlet with the bisacromial diameter in the transverse position. As descent occurs, the bisacromial diameter rotates to an oblique or anteroposterior diameter, until the anterior shoulder rests beneath the pubic symphysis. Delivery of the anterior shoulder occurs as it slips beneath the pubic symphysis. Upward flexion of the body allows for easy delivery of the posterior shoulder over the perineum.

As the shoulders descend, the head engages the pelvic inlet in a transverse or oblique position. Rotation of the head to the occiput anterior position occurs as it enters the midpelvis. The occiput then slips beneath the pubic symphysis, and the remainder of the head is delivered by flexion as the chin, mouth, nose, and forehead slip over the maternal perineum.

As delivery of the breech occurs, increasingly larger diameters (bitrochanteric, bisacromial, biparietal) of the body enter the pelvis, whereas in cephalic presentation, the largest diameter (biparietal diameter) enters the pelvis first. Particularly in preterm labors, the head is considerably larger than the body and provides a better “dilating wedge” as it passes through the cervix and into the pelvis. The smaller bitrochanteric and bisacromial diameters may descend into the pelvis through a partially dilated cervix, but the larger biparietal diameter may be trapped. Delivery in these cases is described in the following.

B. Partial Breech Extraction—

Partial breech extraction (assisted breech extraction) is used when the operator discerns that spontaneous delivery will not occur or that expeditious delivery is indicated for fetal or maternal reasons. The body is allowed to deliver spontaneously up to the level of the umbilicus. The operator then assists in delivery of the legs, shoulders, arms, and head.

As the umbilicus appears at the maternal perineum, the operator places a finger medial to one thigh and then the other thigh, pressing laterally as the fetal pelvis is rotated away from that side by an assistant. Thus, the thigh is externally rotated at the hip and results in flexion of the knee and delivery of one, then the other, leg. The fetal trunk is then wrapped in a towel to support the body. When both scapulae are visible, the body is rotated counterclockwise. The operator locates the right humerus and laterally sweeps the arm across the chest and out the perineum (Fig. 19–3). In a similar fashion, the body is rotated clockwise to deliver the left arm. The head then spontaneously delivers by gently lifting the body upward and applying fundal pressure to maintain flexion of the fetal head (Fig. 19–4). During partial breech extraction, the anterior shoulder may be difficult to deliver if it is impacted behind the pubic symphysis. In this event, the body is gently lifted upward toward the pubic symphysis, and the operator inserts 1 hand along the hollow of the maternal pelvis and identifies the posterior humerus of the fetus. By gentle downward traction on the humerus, the posterior arm can be easily delivered, thus allowing for easier delivery of the anterior shoulder and arm.

The operator may elect to manually assist in delivery of the head by performing the Mauriceau-Smellie-Veitmaneuver (Fig. 19–5). In this procedure, the index and middle fingers of 1 of the operator's hands are applied over the maxilla as the body rests on the palm and forearm of the operator. Two fingers of the operator's other hand are applied on either side of the neck with gentle downward traction. At the same time, the body is elevated toward the pubic symphysis, allowing for controlled delivery of the mouth, nose, and brow over the perineum. Likewise, Piper forceps may be used electively or when the Mauriceau-Smellie-Veit maneuver fails to deliver the aftercoming head. Piper forceps may only be used when the cervix is completely dilated and the head is engaged in the pelvis. Ideally, the head is in a direct occiput anterior position, but a left or right occiput anterior position is acceptable. Piper forceps should not be attempted in the occiput transverse positions because this may result in significant fetal and maternal injury. An assistant supports and slightly elevates the fetal trunk while the operator places each forceps blade alongside the fetal parietal bones (Fig. 19–6). After proper placement is confirmed, the forceps are locked, and gentle traction is applied to flex and deliver the head over the perineum. A midline episiotomy is often indicated to allow for easier application of the forceps and for delivery.

If, after delivery of the body, the spine remains in the posterior position and rotation is unsuccessful, extraction of the head in a persistent occiput posterior position may be accomplished by the modified Prague maneuver. One hand of the operator supports the shoulders from below, while the other hand gently elevates the body upward toward the maternal abdomen. This action flexes the head within the birth canal and results in delivery of the occiput over the perineum.

In premature breech presentations, the incompletely dilated cervix may allow delivery to the smaller body, but the relatively larger aftercoming head may be entrapped. Prompt delivery is mandatory because severe asphyxia leading to death may rapidly ensue. Gentle downward traction on the shoulders combined with fundal pressure applied by an assistant may effect delivery. If this fails, the anesthesiologist should administer nitroglycerin or inhalation anesthesia to obtain complete relaxation of the lower uterine segment and pelvic floor with reattempt at delivery.

If delivery is still not accomplished, Dührssen's incisions must be considered to preserve fetal life. Incisions are made in the posterior cervix at the 6 o'clock position to loosen the entrapped head. Occasionally, additional incisions are necessary at the 2 and 10 o'clock positions. Dührssen's incisions invariably release the fetal head, but the maternal consequences may be severe with resultant hemorrhage. Thus, this procedure should be performed only in an emergent situation. Prevention of head entrapment can be accomplished by delivering viable premature breech gestations by caesarean section.

C. Total Breech Extraction—

In total breech extraction (Fig. 19–7), the entire body is manually delivered. This procedure is used only occasionally when fetal distress is encountered and an expeditious delivery is indicated, and under certain conditions in the setting of delivery of a second twin in a nonvertex position following successful vaginal delivery of a first twin. Total breech extraction has been virtually replaced by caesarean delivery in modern obstetrics.

For complete or footling presentation, total breech extraction is accomplished by initially grasping both feet and applying gentle downward pressure until the buttocks are delivered (Fig. 19–8). A generous midline or mediolateral episiotomy is then performed. The operator gently grasps the fetal pelvis, with both thumbs placed directly on either side of the sacrum. The spine is rotated, if necessary, until it rests under the pubic symphysis. Gentle, firm downward pressure is applied to the body until both scapulas are visible. The shoulders, arms, and head are delivered as in partial breech extraction.

If the fetus is in frank breech presentation, the index finger of the right hand must initially be placed into the anterior groin of the fetus and gentle downward pressure applied (Fig. 19–9). As the fetus descends further into the birth canal, the left index finger is inserted into the posterior groin, and additional gentle downward traction is applied, until the buttocks are delivered through the vaginal introitus (Fig. 19–10). The fetus is gently rotated until the spine rests directly under the pubic symphysis. To deliver the extended legs from the birth canal, the operator places the index finger in the popliteal fossa of 1 leg and applies pressure upward and outward, causing the knee to flex. As the knee flexes, the foot is often seen or easily palpated. The lower leg is grasped firmly and gently delivered, and the opposite leg is then delivered. The rest of the body is extracted as previously described for footling presentation.

D. Internal Podalic Version—

Internal podalic version is now rarely used because of the high fetal and maternal morbidity and mortality associated with the procedure. It is occasionally performed as a life-saving procedure or in cases of a noncephalic second twin (see Chapter 17 for delivery of a second twin). Internal podalic version is the only alternative to caesarean section for rapid delivery of the second twin in a noncephalic presentation if external cephalic version fails. Thus, when caesarean section is unavailable or when a life-threatening condition arises (maternal hemorrhage due to premature placental separation, fetal distress, prolapsed umbilical cord), internal version may be required.

A life-threatening condition is the only indication for internal podalic version. The cervix must be completely dilated, and the membranes must be intact. A skilled operator is crucial for safe performance of this procedure. In several French studies, internal podalic version was found to be a reliable and effective technique with excellent long-term maternal and fetal prognoses.

Internal podalic version is contraindicated in cases in which the membranes are ruptured or oligohydramnios is present, precluding easy version. This procedure should not be performed through a partially dilated cervix or if the uterus is firmly contracted down on the fetal body. However, recent studies have indicated that intravenous nitroglycerin can be used to provide transient uterine relaxation without affecting maternal or fetal outcome.

Internal podalic version is associated with considerable risk of traumatic injury to both fetus and mother. Prior to 1950, when this procedure was performed much more frequently than it is today, associated uterine rupture and hemorrhage caused 5% of all maternal deaths. Perinatal mortality rates were 5–25% (primarily due to traumatic intracerebral hemorrhage and birth asphyxia). Considerable birth trauma, including long bone fractures, dislocations, epiphyseal separations, and central nervous system deficits, was also linked to this procedure. For these reasons, internal podalic version has been abandoned with rare exceptions in favor of caesarean section.

Internal podalic version is performed by first establishing an intravenous line for administration of parenteral fluids, including blood. Cross-matched blood should be available in the hospital blood bank. Anesthesia is then administered to relax the uterus. The patient is then placed in the dorsolithotomy position. The operator's hand is inserted through the fully dilated cervix along the fetal body until both feet are identified, and traction is applied to bring the feet into the pelvis and out the introitus. Then, both feet are firmly grasped. An amniotomy is then performed, and dorsal traction is applied on both lower extremities until both feet are delivered through the vagina. A total breech extraction for delivery of the body is then performed (Fig. 19–11).

Prognosis

The incidence of caesarean section for breech delivery has been steadily increasing, from approximately 30% in 1970 to 85% in 1999. A recent review of breech deliveries in California revealed an 88% caesarean section rate, with more vaginal deliveries performed in public teaching hospitals and far fewer in private facilities. A decreased number of practitioners currently are skilled in vaginal breech delivery, and although academic faculty support its teaching, there are insufficient numbers of vaginal breech deliveries to properly teach this procedure at most institutions. It should be noted that caesarean section for the immature or malformed fetus does not improve chances for perinatal survival; vaginal delivery should be performed in these cases.

The Term Breech Trial Collaborative Group recently conducted a randomized controlled trial to compare planned caesarean section with vaginal birth for selected breech presentation pregnancies. They found that fetuses of women who underwent planned caesarean sections were less likely to die or to experience poor outcomes in the immediate neonatal period than were fetuses of women who underwent vaginal birth. There was no difference in the 2 groups in terms of maternal mortality or serious morbidity. They concluded that a policy of planned caesarean section will result in 7 caesarean births to avoid 1 infant death or serious morbidity. Because of the results of this trial, the American College of Obstetricians and Gynecologists recommends planned caesarean delivery for persistent breech presentations at term.

Essentials of Diagnosis

• Compound presentation is prolapse of a fetal extremity alongside the presenting part.
• Prolapse of the hand in cephalic presentation is most common, followed by prolapse of an upper extremity in breech presentation. Prolapse of a lower extremity in cephalic presentation is relatively rare.
• Compound presentations are uncommon, occurring in only 1 in 1000 pregnancies.

Pathogenesis

Obstetric factors that prevent descent of the presenting part into the pelvic inlet predispose to prolapse of an extremity alongside the presenting part (ie, prematurity, cephalopelvic disproportion, multiple gestation, grand multiparity, and hydramnios). Prematurity occurs in over 50% of compound presentations. In twin gestations, over 90% of compound presentations are associated with the second twin.

Because of poor application of the presenting part to the cervix found in compound presentations, umbilical cord prolapse is common (occurring in 11–20% of cases) and is a major contributor to fetal loss during labor.

Clinical Findings

The diagnosis of compound presentation is made by palpation of a fetal extremity adjacent to the presenting part on vaginal examination. The diagnosis is usually made during labor; as the cervix dilates, the prolapsed extremity is more easily palpated alongside the vertex or breech. Compound presentation may be suspected if poor progress in labor is noted, particularly when the presenting part fails to engage during the active phase. If the diagnosis of compound presentation is suspected but uncertain, ultrasound can be used to locate the position of the extremities and search for malformations.

Complications

Umbilical cord prolapse is a risk in all cases of compound presentation, and continuous fetal heart rate monitoring should be performed to detect fetal distress or changes in the fetal heart rate. Umbilical cord complications should be managed by immediate caesarean delivery (see below).

Treatment

Management of compound presentation depends on gestational age and type of presentation. Given that 50% of compound presentations are associated with prematurity, viability of the fetus should be documented prior to delivery. If the fetus is considered nonviable, labor should be permitted and vaginal delivery anticipated. The small size of the fetus makes dystocia or difficult vaginal delivery uncommon.

Labor can be allowed and vaginal delivery anticipated in viable cephalic presentations with a prolapsed hand. These cases generally pose no difficulty in labor or delivery because the hand moves upward into the lower uterine segment as the vertex descends into the birth canal. Therefore, expectant management (as opposed to manual reduction of the fetal hand into the uterus) is generally advised.

Prognosis

Compound presentations have been associated historically with perinatal mortality rates ranging from 9 to 19%. Contributing factors are prematurity, prolapsed umbilical cord, and traumatic vaginal delivery.

Essentials of Diagnosis

• Shoulder dystocia is defined as an inability to deliver the shoulders after the head has delivered.
• Characteristically, after the head is delivered, the chin presses tightly against the perineum as the anterior shoulder becomes impacted behind the pubic symphysis.
• This condition is an acute obstetric emergency requiring prompt, skillful management in order to prevent significant fetal damage or death.
• The incidence of shoulder dystocia ranges from 0.15 to 1.7% of all vaginal deliveries.

Pathogenesis

Primary risk factors that can influence clinical management are fetal macrosomia, gestational or overt diabetes mellitus, a history of shoulder dystocia in a prior birth, a prolonged second stage of labor, and instrumental delivery, particularly a midpelvic delivery. Other risk factors, such as a history of a macrosomic infant, maternal obesity, multiparity, and postterm pregnancy, are mediated through the primary risk factors. However, most women who experience shoulder dystocia have no combination of risk factors that allows clinically useful identification.

Prevention

Efforts at prevention focus on patients with the clinically important risk factors: history of shoulder dystocia, macrosomia by estimated fetal weight (EFW), diabetes, prolonged second stage of labor, and instrumental delivery. Although no study has shown conclusively that offering caesarean delivery in the presence of various combinations of these risk factors is advisable from a risk–benefit analysis, most practitioners apply some or all of these in an attempt to reduce the risk of shoulder dystocia. An example of one approach follows.

1. Prior shoulder dystocia: Offer caesarean.

2. Prior brachial plexus injury: Strongly suggest caesarean.

3. Nondiabetic with macrosomia by EFW (varying thresholds applied between 4500 and 5000 g): Offer caesarean.

4. Diabetic with macrosomia (varying thresholds applied between 4000 and 4500 g): Offer caesarean.

5. Macrosomia by EFW: Avoid instrumental delivery.

It should be noted that labor induction in a nondiabetic woman due to suspected fetal macrosomia does not decrease the occurrence of shoulder dystocia nor does it decrease the rate of caesarean section.

Clinical Findings

Shoulder dystocia should be anticipated given any indications of macrosomia. The diagnosis is confirmed when gentle downward pressure on the head fails to deliver the anterior shoulder from behind the pubic symphysis. At this point, the fetus is at risk for asphyxiation as the fetus cannot expand its chest to breathe, and umbilical cord circulation is compressed within the birth canal. Confronted with this terrifying dilemma, the inexperienced operator often continues to apply downward pressure on the head in a vain attempt to deliver the anterior shoulder. Such action should be avoided, not only because it is ineffective but also because it can potentially damage the brachial plexus and result in permanent Erb's palsy. A number of maneuvers designed to alleviate shoulder dystocia without increasing traction have been described. No specific sequence of these maneuvers has be shown to be superior to any other, but a commonsense approach based on ease of performance and limitations of risk can be described. Initially, the operator places a hand in the birth canal to assess the posterior outlet. If inadequate, an episiotomy or a proctoepisiotomy is performed. At the same time, assistants including a pediatrician and an anesthesiologist are summoned to aid in the delivery.

Complications

Birth injuries related to shoulder dystocia include fracture of the humerus or clavicle and injury to the brachial plexus (Erb's palsy). Fractures of the humerus and clavicle generally heal without incident, and most injuries to the brachial plexus resolve with minimal or no neurologic deficit detectable during the neonatal period. However, approximately 10% of cases of Erb's palsies do not resolve. Studies attempting to distinguish the clinical course of patients with permanent injuries from those with transient injuries have found no clinically distinct characteristics. Some severe cases of shoulder dystocia may lead to hypoxic-ischemic encephalopathy and possible death. Maternal complications of shoulder dystocia include postpartum hemorrhage and lacerations involving the cervix, vagina, and perineum

Treatment

The McRoberts' maneuver should be used initially because it is simple and resolves shoulder dystocia in 42% of cases. The maternal legs are hyperflexed onto the maternal abdomen, resulting in flattening of the sacrum and cephalad rotation of the symphysis pubis. If the shoulders remain undelivered, suprapubic pressure is applied by an assistant to dislodge the anterior shoulder while gentle downward pressure on the head is applied. Suprapubic pressure and/or proctoepisiotomy increases success rates to between 54% and 58%. If these attempts are unsuccessful, the examiner can attempt to rotate the fetal shoulders into the oblique position by placing 2 fingers against the posterior shoulder and pushing it around toward the fetal chest (Rubin maneuver) or pushing the posterior shoulder around toward the fetal back (Wood's maneuver) in a corkscrew fashion.

If the maneuvers to this point fail, delivery of the posterior arm (Barnum maneuver) is indicated. The obstetrician's hand is inserted posteriorly into the hollow of the maternal sacrum, and the posterior arm of the fetus is identified. Gentle pressure by the examiner's forefinger on the fetal antecubital fossa will cause flexion of the arm. As the arm flexes across the chest, the forearm is gently grasped, and the hand and forearm are gently delivered from the birth canal. If not, the trunk can be rotated to bring the free arm anteriorly, resulting in delivery. Deliberate fracture of the clavicle also can be performed, preferably in a direction away from the fetal lungs. This action diminishes the size of the shoulder girdle and should facilitate delivery.

Finally, if all previous techniques fail, a Zavanelli maneuver can be performed in which the fetal head is replaced in anticipation of a caesarean delivery. A subcutaneous symphysiotomy also can be performed to allow disimpaction of the fetal shoulders. Both of these procedures can be very difficult, are associated with high maternal and fetal morbidity, and should be performed only when other conventional maneuvers have failed.

Prognosis

Women with a history of shoulder dystocia in a prior pregnancy are at increased risk of shoulder dystocia in future pregnancies. Retrospective data put this recurrence risk at 1–25%. It is reasonable to offer women with a history of shoulder dystocia caesarean delivery in future pregnancies.

Essentials of Diagnosis

• Umbilical cord prolapse is defined as descent of the umbilical cord into the lower uterine segment, where it may lie adjacent to the presenting part (occult cord prolapse) or below the presenting part (overt cord prolapse) (Fig. 19–12).
• In occult prolapse, the umbilical cord cannot be palpated during pelvic examination, whereas in funic presentation, which is characterized by prolapse of the umbilical cord below the level of the presenting part before the rupture of membranes occurs, the cord often can be easily palpated through the membranes.
• Overt cord prolapse is associated with rupture of the membranes and displacement of the umbilical cord into the vagina, often through the introitus.

Prolapse of the umbilical cord to a level at or below the presenting part exposes the cord to intermittent compression between the presenting part and the pelvic inlet, cervix, or vaginal canal. Compression of the umbilical cord compromises fetal circulation and, depending on the duration and intensity of compression, may lead to fetal hypoxia, brain damage, and death. In overt cord prolapse, exposure of the umbilical cord to air causes irritation and cooling of the cord, resulting in further vasospasm of the cord vessels. For these reasons, cord prolapse is considered to be an obstetric emergency.

The incidence of overt umbilical cord prolapse in cephalic presentations is 0.5%, frank breech 0.5%, complete breech 5%, footling breech 15%, and transverse lie 20%. The incidence of occult prolapse is unknown because it can be detected only by fetal heart rate changes characteristic of umbilical cord compression. However, some degree of occult prolapse appears to be common, given that as many as 50% of monitored labors demonstrate fetal heart rate changes compatible with umbilical cord compression. In most cases, the compression is transient and can be rectified simply by changing the patient's position.

Whether occult or overt, umbilical cord prolapse is associated with significant rates of perinatal morbidity and mortality because of intermittent compression of blood flow and resultant fetal hypoxia. The perinatal mortality rate associated with all cases of overt umbilical cord prolapse approaches 20%. Prematurity, itself a contributor to the incidence of umbilical cord prolapse, accounts for a considerable portion of this perinatal loss.

Pathogenesis

Any obstetric condition that predisposes to poor application of the fetal presenting part to the cervix can result in prolapse of the umbilical cord. Cord prolapse is associated with prematurity (<34 weeks' gestation), abnormal presentations (breech, brow, compound, face, transverse), occiput posterior positions of the head, pelvic tumors, multiparity, placenta previa, low-lying placenta, and cephalopelvic disproportion. In addition, cord prolapse is possible with polyhydramnios, multiple gestation, or premature rupture of the membranes occurring before engagement of the presenting part. A recent study revealed that obstetric intervention contributes to nearly half of cases of umbilical cord prolapse. Examples cited include amniotomy, scalp electrode application, intrauterine pressure catheter insertion, attempted external cephalic version, and expectant management of preterm premature rupture of membranes.

Prevention

Patients at risk for umbilical cord prolapse should be treated as high-risk patients. Patients with fetal malpresentation or poorly applied cephalic presentations should be considered for ultrasonographic examination at the onset of labor to determine fetal lie and cord position within the uterine cavity. Because most prolapses occur during labor as the cervix dilates, patients at risk for cord prolapse should be continuously monitored to detect abnormalities of the fetal heart rate. Artificial rupture of membranes should be avoided until the presenting part is well applied to the cervix. At the time of spontaneous membrane rupture, a prompt, careful pelvic examination should be performed to rule out cord prolapse. Should amniotomy be required and the presenting part remains unengaged, careful needling of the membranes and slow release of the amniotic fluid can be performed until the presenting part settles against the cervix.

Clinical Findings

Overt Cord Prolapse

Overt cord prolapse can be diagnosed simply by visualizing the cord protruding from the introitus or by palpating loops of cord in the vaginal canal.

Funic Presentation

The diagnosis of funic presentation is made by pelvic examination if loops of cord are palpated through the membranes. Antepartum detection of funic presentation is discussed below.

Occult Prolapse

Occult prolapse is rarely palpated during pelvic examination. This condition can be inferred only if fetal heart rate changes (variable decelerations, bradycardia, or both) associated with intermittent compression of the umbilical cord are detected during monitoring.

Complications

Fetus

The fetus in good condition whose well-being is jeopardized by umbilical cord compression may exhibit violent activity readily apparent to the patient and the obstetrician. Variable fetal heart rate decelerations will occur during uterine contractions, with prompt return of the heart rate to normal as each contraction subsides. If cord compression is complete and prolonged, fetal bradycardia occurs. Persistent, severe, variable decelerations and bradycardia lead to development of hypoxia, metabolic acidosis, and eventual damage or death. As the fetal status deteriorates, activity lessens and eventually ceases. Meconium staining of the amniotic fluid may be noted at the time of membrane rupture.

Maternal

Caesarean section is a major operative procedure with known anesthetic, hemorrhagic, and operative complications. These risks must be weighed against the real risk to the fetus of continued hypoxia if labor were to continue.

Maternal risks encountered at vaginal delivery include laceration of the cervix, vagina, or perineum resulting from a hastily performed delivery.

Neonatal

The neonate at delivery may be hypoxic, acidotic, or moribund. A pediatric team should be present to effect immediate resuscitation of the newborn.

Treatment

Overt Cord Prolapse

The diagnosis of overt cord prolapse demands immediate action to preserve the life of the fetus. An immediate pelvic examination should be performed to determine cervical effacement and dilatation, station of the presenting part, and strength and frequency of pulsations within the cord vessels. If the fetus is viable, the patient should be placed in the knee–chest position, and the examiner should apply continuous upward pressure against the presenting part to lift and maintain the fetus away from the prolapsed cord until preparations for caesarean delivery are complete. Alternatively, 400–700 mL of saline can be instilled into the bladder in order to elevate the presenting part. Oxygen should be given to the mother until the anesthesiologist is prepared to administer a rapid-acting inhalation anesthetic for delivery. Successful reduction of the prolapsed umbilical cord has been described, but such an attempt may worsen fetal heart rate changes and should not delay preparation for caesarean delivery. Abdominal delivery should be accomplished as rapidly as possible through a generous midline abdominal incision, and a pediatric team should be on standby in the event immediate resuscitation of the newborn is necessary.

Occult Cord Prolapse

If cord compression patterns (variable decelerations) of the fetal heart rate are recognized during labor, an immediate pelvic examination should be performed to rule out overt cord prolapse. If occult cord prolapse is suspected, the patient should be placed in the lateral Sims or Trendelenburg position in an attempt to alleviate cord compression. If the fetal heart rate returns to normal, labor can be allowed to continue, provided no further fetal insult occurs. Oxygen should be administered to the mother, and the fetal heart rate should be continuously monitored electronically. Amnioinfusion can be performed via an intrauterine pressure catheter in order to instill fluid within the uterine cavity and possibly decrease the incidence of variable decelerations. If the cord compression pattern persists or recurs to the point of fetal jeopardy (moderate to severe variable decelerations or bradycardia), a rapid caesarean section should be accomplished.

Funic Presentation

The patient at term with funic presentation should be delivered by caesarean section prior to membrane rupture. However, there is no consensus on management if the fetus is premature. The most conservative approach is to hospitalize the patient on bed rest in the Sims or Trendelenburg position in an attempt to reposition the cord within the uterine cavity. Serial ultrasonographic examinations should be performed to ascertain cord position, presentation, and gestational age.

Route of Delivery

Vaginal delivery can be successfully accomplished in cases of overt or occult cord prolapse if, at the time of prolapse, the cervix is fully dilated, cephalopelvic disproportion is not anticipated, and an experienced physician determines that delivery is imminent. Internal podalic version, midforceps rotation, or any other operative technique is generally more hazardous to mother and fetus in this situation than is a judiciously performed caesarean delivery. Caesarean delivery is the preferred route of delivery in most cases. Vaginal delivery is the route of choice for the previable or dead fetus.

Prognosis

Maternal

Maternal complications include those related to anesthesia, blood loss, and infection following caesarean section or operative vaginal delivery. Maternal recovery is generally complete.

Neonatal

Although the prognosis for intrapartum cord prolapse is greatly improved, fetal mortality and morbidity rates still can be high, depending on the degree and duration of umbilical cord compression occurring before the diagnosis is made and neonatal resuscitation is started. If the diagnosis is made early and the duration of complete cord occlusion is < 5 minutes, the prognosis is good. Gestational age and trauma at delivery also affect the final neonatal outcome. If complete cord occlusion has occurred for longer than 5 minutes or if intermittent partial cord occlusion has occurred over a prolonged period of time, fetal damage or death may occur.