1. Dystocia: Abnormal Labor
Barış Kaya,MD,
Asst. Prof.
Near East University Faculty of Medicine

2. In 2007, the cesarean delivery rate was 31
In 2007, the cesarean delivery rate was 31.8 percent—the highest level ever reported for the United States.
According to the American College of Obstetricians and Gynecologists (2003), approximately 60 percent of primary cesarean deliveries in the United States are attributable to the diagnosis of dystocia.
Roy (2003) has proposed that this high frequency results from environmental changes that are developing more rapidly than Darwinian natural selection.
Humans are poorly adapted to the affluence of the modern diet, and one result is dystocia.
Evidence in support of this comes from Barau and associates (2006), who analyzed prepregnancy body mass index (BMI) and the risk of cesarean delivery.
It is reported that obesity is associated with an increased cesarean delivery rate.

3. Dystocia literally means difficult labor and is characterized by
abnormally slow labor progress.
It arises from four distinct abnormalities that may exist singly or in combination:
1. Abnormalities of the expulsive forces. Uterine contractions may be insufficiently strong or inappropriately coordinated to efface and dilate the cervix—uterine dysfunction. Also ,there may be inadequate voluntary maternal muscle effort during second-stage labor.
2. Abnormalities of presentation, position, or development of the fetus.
3. Abnormalities of the maternal bony pelvis—that is, pelvic contraction.
4. Abnormalities of soft tissues of the reproductive tract that form an obstacle to fetal descent

4. the power- uterine contractility and maternal expulsive effort
the passenger —the fetus;
the passage —the pelvis.

5. Common Clinical Findings in Women with Ineffective Labor
Inadequate cervical dilation or fetal descent:
Protracted labor—slow progress (at least 4 hour with regular contraction with more than 6 cm cx dilatation for active phase of first phase with ruptured membranes)
Arrested labor—no progress, 3 h (nullipar), 2 h multipar in second stage)
Fetopelvic disproportion:
Excessive fetal size
Inadequate pelvic capacity
Malpresentation or position of the fetus

6. The expression ‘cephalopelvic disproportion’ came into use prior to the 20th century to describe obstructed labor resulting from disparity between the size of the fetal head and maternal pelvis.
‘Failure to progress’ , this term is used to include lack of progressive cervical dilatation or lack of fetal descent

7. The diagnosis of uterine dysfunction in the latent phase is difficult and sometimes can be made only in retrospect.
Women who are not yet in active labor commonly are erroneously treated for uterine dysfunction.
Opioid medication (Ex: Morphin) and bed rest is good option in the management of prolonged latent phase (20 hour for nullipar, 14 hour for multipar)
Induction with Oxytocin or amniotomy are other options however cesarean section should be avoided in the latent phase !

8. It is possible to define two types of uterine dysfunction.
In the more common hypotonic uterine dysfunction, there is no basal hypertonus and uterine contractions have a normal gradient pattern (synchronous), but pressure during a contraction is insufficient to dilate the cervix.
In the second type, hypertonic uterine dysfunction or incoordinate uterine dysfunction, either basal tone is elevated appreciably or the pressure gradient is distorted.
Gradient distortion may result from contraction of the uterine midsegment with more force than the fundus or from complete asynchronism of the impulses originating in each cornu or a combination of these two.

9. Active-Phase Disorders
Labor abnormalities are clinically divided into either slower than- normal progress—protraction disorder—or complete cessation of progress—arrest disorder.
In history, Friedman’s curve about normal labor progression has been changed by Zhang et al. termed as ‘Contemporary obstetric practice’
A woman must be in the active phase of labor with cervical dilatation to at least 6 cm with ruptured membranes.
At least 4 hour no cervical change with regular contractions is defined as ‘arrest of labor’.

10. Protraction disorders are less well described, and the time necessary before diagnosing slow progress is undefined.
The World Health Organization (1994) has proposed a labor management partograph to evaluate cervlcal changes.
It is reported that when labor is effectively induced or augmented with oxytocin, 90 percent of women achieve 200 to 225 Montevideo units, and 40 percent achieve at least 300 Montevideo units.
These results suggest that there are certain minimums of uterine activity that should be achieved before performing cesarean delivery for dystocia.

11. Before the diagnosis of arrest during first-stage labor is made, both of these criteria should be met (ACOG):
The latent phase has been completed, and the cervix is dilated 6 cm or more.
A uterine contraction pattern of 200 Montevideo units or more in a 10-minute period has been present for 4 hours without cervical change.

12. Second-Stage Disorders
The second stage incorporates many of the cardinal movements necessary for the fetus to negotiate the birth canal.
Accordingly, disproportion of the fetus and pelvis frequently becomes apparent during second-stage labor.
The second stage in nulliparas was limited to 3 hours and extended to 4 hours when regional analgesia was used.
For multiparas, 2 hour was the limit, extended to 3 hours with regional analgesia.

13. Epidural Analgesia
Epidural analgesia has been associated with lengthening of both first- and second-stage labor and with slowing of the rate of fetal descent.
Chorioamnionitis:
Because of the association of prolonged labor with maternal intrapartum infection, some clinicians have suggested that infection itself contributes to abnormal uterine activity.
It is likely that uterine infection in this clinical setting is a consequence of dysfunctional, prolonged labor rather than a cause of dystocia.

14. RUPTURED MEMBRANES WITHOUT LABOR
Membrane rupture at term without spontaneous uterine contractions complicates approximately 8 % of pregnancies.
Management generally included labor stimulation if contractions did not begin after 6 to 12 hours.
Reports of lower rates of chorioamnionitis, metritis, and NICU admissions for women with term ruptured membranes whose labors were induced compared with those managed expectantly

15. PRECIPITOUS LABOR AND DELIVERY
Precipitous labor is extremely rapid labor and delivery.
It may result from an abnormally low resistance of the soft parts of the birth canal, from abnormally strong uterine and abdominal contractions, or rarely from the absence of painful sensations and thus a lack of awareness of vigorous labor.
Precipitous labor and delivery seldom are accompanied by serious maternal complications if the cervix is effaced appreciably and compliant, if the vagina has been stretched previously, and if the perineum is relaxed.

16. Vigorous uterine contractions combined with a long, firm cervix and a noncompliant birth canal may lead to uterine rupture or extensive lacerations of the cervix, vagina, vulva, or perineum.
It is in these latter circumstances that the rare condition of amnionic fluid embolism most likely develops .
Short labors were defined as a rate of cervical dilatation of 5 cm/hr or faster for nulliparas and 10 cm/hr for multiparas.
Such short labors were associated with placental abruption, meconium, postpartum hemorrhage, cocaine abuse, and low Apgar scores.

17. Treatment of rapid labor
The use of tocolytic agents such as magnesium sulfate is unproven in these circumstances.
Certainly, any oxytocin agents being administered should be stopped immediately.

18. FETOPELVIC DISPROPORTION
Fetopelvic disproportion arises from diminished pelvic capacity, excessive fetal size, or more usually, a combination of both.
There may be contractions of the pelvic inlet, the mid pelvis, or the pelvic outlet, or a generally contracted pelvis may be caused by combinations of these.

19. Contracted Inlet
The pelvic inlet usually is considered to be contracted if its shortest antero-posterior diameter is less than 10 cm or if the greatest transverse diameter is less than 12 cm.
The anteroposterior diameter of the inlet is commonly approximated by manually measuring the diagonal conjugate, which is approximately 1.5 cm greater. Therefore, inlet contraction usually is defined as a diagonal conjugate of less than 11.5 cm.
Occasionally, the body of the first sacral vertebra is displaced forward so that the shortest distance may actually be between this abnormal sacral promontory and the symphysis pubis.

20. Pelvic planes

22. A contracted inlet plays an important part in the production of abnormal presentations.
Cephalic presentations still predominate, but the head floats freely over the pelvic inlet or rests more laterally in one of the iliac fossae.
In women with contracted pelvis, face and shoulder presentations are encountered three times more frequently, and the cord prolapses four to six times more often.

23. Mid-pelvis contraction
The obstetrical plane of the midpelvis extends from the inferior margin of the symphysis pubis through the ischial spines and touches the sacrum near the junction of the fourth and fifth vertebrae .

24. The definition of midpelvic contractions has not been established with the same precision possible for inlet contractions.
There is reason to suspect midpelvic contraction whenever the interspinous diameter is less than 10 cm.
Although there is no precise manual method of measuring midpelvic dimensions, a suggestion of contraction sometimes can be inferred if the spines are prominent, the pelvic sidewalls converge, or the sacrosciatic notch is narrow
A normal intertuberous diameter, however, does not always exclude a narrow interspinous diameter.

25. Pelvic outlet contraction
This finding usually is defined as an interischial tuberous diameter of 8 cm or less. The pelvic outlet may be roughly likened to two triangles, with the interischial tuberous diameter constituting the base of both.
A contracted outlet may cause dystocia not so much by itself as through the often- associated midpelvic contraction.
Outlet contraction without concomitant midplane contraction is rare.

26. It may play an important part in the production of perineal tears.
With increasing narrowing of the pubic arch, the occiput cannot emerge directly beneath the symphysis pubis but is forced increasingly farther down upon the ischiopubic rami.
The perineum, consequently, becomes increasingly distended and thus exposed to greater danger of laceration.

27. Estimation of Pelvic Capacity
Briefly, the examiner attempts to judge the anteroposterior diameter of the inlet—the diagonal conjugate, the interspinous diameter of the midpelvis, and the intertuberous distances of the pelvic outlet.
A narrow pelvic arch of less than 90 degrees can signify a narrow pelvis. An unengaged fetal head can indicate either excessive fetal head size or reduced pelvic inlet capacity.
X-Ray Pelvimetry: Even when widely used, the prognosis for successful vaginal delivery in any given pregnancy cannot be established using x-ray pelvimetry alone.

28. Computed Tomographic (CT) Scanning
Advantages of CT pelvimetry, compared with those of conventional x-ray pelvimetry include reduced radiation exposure, greater accuracy, and easier performance.
With conventional x-ray pelvimetry, the mean gonadal exposure is estimated by the Committee on Radiological Hazards to Patients to be 885 mrad .
Depending on the machine and technique employed, fetal doses with computed tomography may range from 250 to 1500 mrad
Magnetic Resonance (MR) Imaging: The advantages of MR pelvimetry include lack of ionizing radiation, accurate measurements, complete fetal imaging, and the potential for evaluating soft tissue dystocia .

29. Fetal Dimensions in Fetopelvic Disproportion
Fetal size alone is seldom a suitable explanation for failed labor !
Most cases of disproportion arise in fetuses whose weight is well within the range of the general obstetrical population.
Thus, other factors, such as malposition of the head, obstruct fetal passage through the birth canal. These include asynclitism, occiput posterior position, and face and brow presentations.
Efforts to clinically and radiographically predict fetopelvic disproportion based on fetal head size have proved disappointing.

30. Face presentation: With this presentation, the head is hyperextended so that the occiput is in contact with the fetal back, and the chin (mentum) is presenting.
The fetal face may present with the chin (mentum) anteriorly or posteriorly, relative to the maternal symphysis pubis .
Although many may persist, many mentum posterior presentations convert spontaneously to anterior even in late labor.
If not, the fetal brow (bregma) is pressed against the maternal symphysis pubis. This position precludes flexion of the fetal head necessary to negotiate the birth canal.

31. Face presentation
Preterm infants, with their smaller head dimensions, can engage prior to conversion to vertex position
Fetal malformations and polyhydramnios were risk factors for face or brow presentations.
Anencephalic fetuses naturally present by the face.
Extended positions develop more frequently when the pelvis is contracted or the fetus is very large

32. High parity is a predisposing factor to face presentation.
It is possible to mistake a breech for a face presentation because the anus may be mistaken for the mouth and the ischial tuberosities for the malar prominences 
Birth of the head from a mentum posterior position is nearly impossible however mentum anterior delivery is possiple.

33. Mentum anterior-posterior

34. Brow Presentation
This rare presentation is diagnosed when that portion of the fetal head between the orbital ridge and the anterior fontanel presents at the pelvic inlet.
The fetal head thus occupies a position midway between full flexion (occiput) and extension (face).
Engagement of the fetal head and subsequent delivery cannot take place as long as the brow presentation persists.
The causes of persistent brow presentation are the same as those for face presentation.
The frontal sutures, large anterior fontanel, orbital ridges, eyes, and root of the nose are felt on vaginal examination, but neither the mouth nor the chin is palpable.

36. Engagement is impossible until there is marked molding that shortens the occipitomental diameter or more commonly, until there is either flexion to an occiput presentation or extension to a face presentation.
In transient brow presentations, the prognosis depends on the ultimate presentation.
If the brow persists, prognosis is poor for vaginal delivery unless the fetus is small or the birth canal is large.
Principles of management are the same as those for a face presentation.

37. Transverse Lie
In this position, the long axis of the fetus is approximately perpendicular to that of the mother.
When the long axis forms an acute angle, an oblique lie results. The latter is usually only transitory, because either a longitudinal or transverse lie commonly results when labor supervenes.
Some calls the oblique lie an unstable lie .
In a transverse lie, the shoulder is usually positioned over the pelvic inlet. The head occupies one iliac fossa, and the breech the other.
This creates a shoulder presentation in which the side of the mother on which the acromion rests determines the designation of the lie as right or left acromial. .
Transverse lie was found 0.3 percent.

38. Etiology
(1) abdominal wall relaxation from high parity,
(2) preterm fetus
(3) placenta previa,
(4) abnormal uterine anatomy,
(5) Hydramnios
(6) contracted pelvis.

39. Mechanism of Labor
Spontaneous delivery of a fully developed newborn is impossible with a persistent transverse lie.
After rupture of the membranes, if labor continues, the fetal shoulder is forced into the pelvis, and the corresponding arm frequently prolapses As labor continues, the shoulder is impacted firmly in the upper part of the pelvis.
The uterus then contracts vigorously in an unsuccessful attempt to overcome the obstacle. With time, a retraction ring rises increasingly higher and becomes more marked. With this neglected transverse lie, the uterus will eventually rupture. Cord prolapsus risk is very high.

41. If the fetus is small—usually less than 800 g—and the pelvis is large, spontaneous delivery is possible despite persistence of the abnormal lie (conduplicato corpore )
The fetus is compressed with the head forced against its abdomen. The head and thorax then pass through the pelvic cavity at the same time.

42. Management of transvers lie
Active labor in a woman with a transverse lie is usually an indication for cesarean delivery.
Before labor or early in labor, with the membranes intact, attempts at external version are worthwhile in the absence of other complications.
If the fetal head can be maneuvered by abdominal manipulation into the pelvis, it should be held there during the next several contractions in an attempt to fix the head in the pelvis.
With cesarean delivery, because neither the feet nor the head of the fetus occupies the lower uterine segment, a low transverse incision into the uterus may lead to difficult fetal extraction. This is especially true of dorsoanterior presentations. Therefore, a vertical incision is typically indicated.

43. Compound Presentation
In a compound presentation, an extremity prolapses alongside the presenting part, and both present simultaneously in the pelvis .
Incidence and Etiology: A hand or arm prolapsed alongside the head once an incidence of approximately 1 in 1000.
In most cases, the prolapsed part should be left alone, because most often it will not interfere with labor.
If the arm is prolapsed alongside the head, the condition should be observed closely to ascertain whether the arm retracts out of the way with descent of the presenting part.
If it fails to retract and if it appears to prevent descent of the head, the prolapsed arm should be pushed gently upward and the head simultaneously downward by fundal pressure.

45. Tebes and co-workers (1999) described a tragic outcome in a newborn delivered spontaneously with the hand alongside the head.
The infant developed ischemic necrosis of the presenting forearm, which required amputation. In general, rates of perinatal mortality and morbidity are increased as a result of concomitant preterm delivery, prolapsed cord, and traumatic obstetrical procedures.

46. Prior to labor, the fetal biparietal diameter has been shown to average from 9.5 to as much as 9.8 cm.
It is demonstrated that the incidence of difficult deliveries is increased to a similar degree when either the anteroposterior diameter of the inlet is less than 10 cm or the transverse diameter is less than 12 cm.
As expected, when both diameters are contracted, dystocia is much greater than when only one is contracted.

47. Persistent Occiput Posterior Position
Most occiput posterior positions undergo spontaneous anterior rotation followed by uncomplicated delivery
Early in labor, approximately 15 percent of fetuses were occiput posterior, and 5 percent were in this position at delivery.
Importantly, two thirds of occiput posterior deliveries occurred with fetuses who were occiput anterior at the beginning of labor.
Thus, most occiput posterior presentations at delivery are the result of malrotation of occiput anterior position during labor, and almost 90 percent of occiput posterior presentations at the outset of labor spontaneously rotate anteriorly.

48. Occiput posterior and anterior fontanel

49. Courtesy of Dr Baris Kaya

50. In most instances, delivery usually can be accomplished without great difficulty once the head reaches the perineum.
The possibilities for vaginal delivery are: (1) spontaneous delivery,
(2) forceps delivery with the occiput posterior,
(3) manual rotation to the occiput anterior followed by spontaneous or forceps delivery
(4) forceps rotation to occiput anterior and delivery.

51. Outcome
Virtually every possible delivery complication was found more frequently with a persistent occiput posterior.
Only half of these women delivered spontaneously, and they accounted for 9 percent of cesarean deliveries performed.
In addition, occiput posterior position at delivery was associated with increased adverse short-term neonatal outcomes.

52. Dystocia from Hydrocephalus
Macrocephaly from excessive accumulation of cerebrospinal fluid may prohibit vaginal delivery.
Normal fetal head circumference at term ranges between 32 and 38 cm.
With hydrocephalus, the circumference often exceeds 50 cm and may reach 80 cm.
Associated defects are frequent, especially neural-tube defects.
Breech presentation is found in at least a third of fetuses and may present problems in undiagnosed cases.

53. Management. If the biparietal diameter (BPD) is 10 cm or if the head circumference is 36 cm, vaginal delivery may be permitted.
In many cases, however, the macrocephalic head must be reduced in size to deliver it.
Removal of fluid by cephalocentesis was a mainstay in the historical intrapartum management of hydrocephalus, but it has come under considerable scrutiny in recent years.

54. Fetal Abdominal Distension
Enlargement of the fetal abdomen sufficient to cause dystocia is usually the result of a greatly distended bladder, ascites, or enlargement of the kidneys or liver.
Occasionally, the edematous fetal abdomen may attain such proportions that spontaneous delivery is impossible.
These abnormalities are frequently diagnosed sonographically before delivery, and the decision must be made whether or not to perform cesarean delivery.
In general, fetal prognosis is poor, regardless of the delivery method.

55. SHOULDER ! DYSTOCIA
The mean head-to-body delivery time in normal births was 24 seconds compared with 79 seconds in those with shoulder dystocia.
These investigators proposed that a head-to-body delivery time exceeding 60 seconds be used to define shoulder dystocia.
Current reports cite an incidence of shoulder dystocia that varies between 0.6 percent and 1.4 percent.

56. There is evidence that the incidence of shoulder dystocia has increased in recent decades, likely due to increasing birthweight .
Gross fetal birthweight—macrosomia —is important, but distribution of excessive tissue with large-for-gestational age infants is also important in its etiology.

57. Maternal Consequences
Postpartum hemorrhage, usually from uterine atony, but also from vaginal and cervical lacerations, is the major maternal risk from shoulder dystocia.

58. Fetal Consequences
Shoulder dystocia may be associated with significant fetal morbidity and even mortality.
Erb or Duchenne brachial plexopathy accounted for two thirds of injuries.
It usually results from stretch on the plexus during passage of the fetus through the birth canal and subsequent delivery. Downward traction on the brachial plexus during delivery of the anterior shoulder is thought to present a particular risk for such stretch.
Importantly, 88 percent of the injuries resolved by 1 year of life.
38 percent had a clavicular fracture, and 17 percent sustained a humeral fracture.

60. Clavicular Fracture
These fractures are relatively common and have been diagnosed in 0.4 percent of newborns delivered vaginally .
Although at times associated with shoulder dystocia, the clavicle often fractures without any suspect clinical events.
Investigators have concluded that isolated clavicular fractures are unavoidable, unpredictable, and have no clinical consequences.

61. Prediction and Prevention of Shoulder Dystocia
There has been considerable evolution in obstetrical thinking about the preventability of shoulder dystocia.
Although there are clearly several risk factors associated with shoulder dystocia, identification of individual instances before the fact has proven to be impossible.

62. Risk Factors
Several, including obesity, multiparity, and diabetes, all exert their effects because of associated increased birthweight.
Shoulder dystocia in 7 percent of pregnancies complicated by gestational diabetes.
Similarly, the association of postterm pregnancy with shoulder dystocia is likely because many fetuses continue to grow after 42 weeks .
Clearly, shoulder dystocia rates increase with greater birthweight, but almost half of the newborns with shoulder dystocia weighed less than g.

63. Summary
ACOG (2002):
1. Most cases of shoulder dystocia cannot be accurately predicted or prevented.
2. Elective induction of labor or elective cesarean delivery for all women suspected of having a macrosomic fetus is not appropriate.
3. Planned cesarean delivery may be considered for the nondiabetic woman with a fetus whose estimated fetal weight is 5000 g or for the diabetic woman whose fetus is estimated to weigh g.

64. Management
Because shoulder dystocia cannot be accurately predicted, clinicians should be well versed in its management principles.
Following delivery of the head, the umbilical cord is compressed within the vagina, and fetal oxygenation declines.
Thus, reduction in the time from delivery of the head to delivery of the body is of great importance for survival.
An initial gentle attempt at traction, assisted by maternal expulsive efforts, is recommended.

65. Moderate suprapubic pressure can be applied by an assistant while downward traction is applied to the fetal head.
The McRoberts maneuver: The maneuver consists of removing the legs from the stirrups and sharply flexing them up onto the abdomen.
Although this does not increase pelvic dimensions, pelvic rotation cephalad tends to free the impacted anterior shoulder.

67. Woods (1943) reported that by progressively rotating the posterior shoulder 180 degrees in a corkscrew fashion, the impacted anterior shoulder could be released. This is frequently referred to as the Woods corkscrew maneuver.
Delivery of the posterior shoulder consists of carefully sweeping the posterior arm of the fetus across the chest, followed by delivery of the arm.
The shoulder girdle is then rotated into one of the oblique diameters of the pelvis with subsequent delivery of the anterior shoulder.

68. Rubin (1964) recommended two maneuvers
Rubin (1964) recommended two maneuvers. First, the fetal shoulders are rocked from side to side by applying force to the maternal abdomen. If this is not successful, the pelvic hand reaches the most easily accessible fetal shoulder, which is then pushed toward the anterior surface of the chest.
This maneuver most often results in abduction of both shoulders, which in turn produces a smaller shoulder-to-shoulder diameter. This permits displacement of the anterior shoulder from behind the symphysis pubis.

69. Deliberate fracture of the clavicle by pressing the anterior clavicle against the pubic ramus can be performed to free the shoulder impaction.
If successful, the fracture will heal rapidly and is usually trivial compared with brachial nerve injury, asphyxia, or death.
Strong fundal pressure, however, applied at the wrong time may result in even further impaction of the anterior shoulder. Gross and associates (1987) reported that fundal pressure in the absence of other maneuvers “resulted in a 77-percent complication rate and was strongly associated with (fetal) orthopedic and neurologic damage !

70. Sandberg (1985) reported the Zavanelli maneuver for cephalic replacement into the pelvis followed by cesarean delivery. The first part of the maneuver consists of returning the head to the occiput anterior or posterior position.
The operator flexes the head and slowly pushes it back into the vagina, following which cesarean delivery is performed.
Terbutaline, 0.25 mg, is given subcutaneously to produce uterine relaxation.
Despite successful replacement, fetal injuries were still common in the desperate circumstances under which the Zavanelli maneuver was used.
Uterine rupture and dislocation of the cervical spine injury were reported with this maneuver.

71. Cleidotomy consists of cutting the clavicle with scissors or other sharp instruments and is usually used for a dead fetus .
Symphysiotomy also has been applied successfully, as described by Hartfield (1986).
Goodwin and colleagues (1997) reported three cases in which symphysiotomy was performed after the Zavanelli maneuver had failed. All three neonates died, and maternal morbidity was significant due to urinary tract injury.

72. Emergency management of an impacted shoulder
1. Call for help—mobilize assistants, an anesthesiologist, and a pediatrician.
2. A generous episiotomy—consider mediolateral or episioproctotomy—may afford room posteriorly.
3. Suprapubic pressure is used initially by most practitioners because it has the advantage of simplicity. Only one assistant is needed to provide suprapubic pressure while normal downward traction is applied to the fetal head.
4. The McRoberts maneuver requires two assistants. Each assistant grasps a leg and sharply flexes the maternal thigh against the abdomen.

73. These maneuvers will resolve most cases of shoulder dystocia. If
they fail, however, the following steps may be attempted:
1. The Woods screw maneuver.
2. Delivery of the posterior arm is attempted, but with a fully extended arm, this is usually difficult to accomplish.
** Other techniques generally should be reserved for cases in which all other maneuvers have failed. These include intentional fracture of the anterior clavicle or humerus and the Zavanelli maneuver.
** There is no evidence that any one maneuver is superior to another in releasing an impacted shoulder or reducing the chance of injury.
Performance of the McRoberts maneuver, however, was deemed a reasonable initial approach.

74. Maternal Complications
Postpartum hemorrhage from atony is increased with prolonged and augmented labors.
Hemorrhage from cesarean delivery is contributory, and there is a higher incidence of uterine tears with hysterotomy if the fetal head is impacted in the pelvis.
Uterine Rupture: Abnormal thinning of the lower uterine segment creates a serious danger during prolonged labor, particularly in women of high parity and in those with a prior cesarean delivery.
When disproportion is so pronounced that there is no engagement or descent, the lower uterine segment becomes increasingly stretched, and rupture may follow. In such cases, there is usually an exaggeration of the normal contraction ring.

75. Pathological Retraction Ring
Localized rings or constrictions of the uterus develop in association with prolonged obstructed labors that are seldom encountered today.
The pathological retraction ring of Bandl is associated with marked stretching and thinning of the lower uterine segment.
** The ring may be seen clearly as a uterine indentation and signifies impending rupture of the lower uterine segment.
** Following birth of a first twin, a pathological ring may still develop occasionally as hourglass constrictions of the uterus.

76. Fistula Formation
With dystocia, the presenting part is firmly wedged into the pelvic inlet and does not advance for a considerable time.
Tissues of the birth canal lying between the leading part and the pelvic wall may be subjected to excessive pressure.
Because of impaired circulation, necrosis may result and become evident several days after delivery as vesicovaginal, vesicocervical, or rectovaginal fistulas.
Most often, pressure necrosis follows a very prolonged second stage.

77. Pelvic Floor Injury
Injury to the pelvic floor muscles, nerve supply, or interconnecting fascia is a common consequence of vaginal delivery, particularly if the delivery is difficult.
During childbirth, the pelvic floor is exposed to direct compression from the fetal head and to downward pressure from maternal expulsive efforts.
These forces stretch and distend the pelvic floor, resulting in functional and anatomical alterations in the muscles, nerves, and connective tissues.
There is accumulating concern that such effects on the pelvic floor during childbirth lead to urinary and anal incontinence and to pelvic organ prolapse.
The anal sphincter is torn in 3 to 6 percent of deliveries, and approximately half of these women report subsequent fecal or gas incontinence.

78. Postpartum Lower Extremity Nerve Injury
The most common mechanism is external compression of the peroneal nerve, usually caused by inappropriate leg positioning in stirrups, especially during a prolonged second-stage labor.
Fortunately, symptoms resolve within 6 months of delivery in most women.

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