Abn labor.pptx & term & preterm labor.pptx

نکات مهم لیبر طبیعی و غیر طبیعی در بارداری

1. Abnormal Labor

2. Abnormalities of the expulsive forces 01

3. Types of Uterine Dysfunction Normal spontaneous contractions can exert pressures approximating 60 mm Hg. Even so, the lower limit of contraction pressure required to dilate the cervix is 15 mm Hg. In abnormal labor, two physiological types of uterine dysfunction may develop. In the more common hypotonic uterine dysfunction, basal tone is normal and uterine contractions have a normal gradient pattern. However, 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.

4. Risk Factors for Uterine Dysfunction First, neuraxial analgesia can slow labor and has been associated with longer first and second stages of labor. Chorioamnionitis is associated with prolonged labor. Uterine infection may directly contribute to uterine dysfunction or instead may simply be an associated consequence of prolonged, dysfunctional labor. A higher station at the onset of labor is significantly linked with subsequent dystocia. Although a risk factor, most nulliparas without fetal head engagement at diagnosis of active labor still deliver vaginally. Maternal obesity lengthens the first stages of labor by 30 to 60 minutes in nulliparas, even after adjusting for associated diabetes, fetal weight, and parity. Dystocia-associated cesarean delivery rates are higher in this group

5. Labor Disorders Latent-phase Prolongation The latent phase may be prolonged, which is defined as >20 hours in the nullipara and >14 hours in the multipara The diagnosis of uterine dysfunction in the latent phase is difficult and commonly is made retrospectively. Women who are not yet in active labor often are erroneously treated for perceived uterine dysfunction.

6. Abnormal Labor Patterns, Diagnostic Criteria, and Methods of Treatment

7. Active-phase Disorders In active labor, disorders are divided into those with slow progress—a protraction disorder or those with halted progress—an arrest disorder.

8. Active-phase Protraction Previously, protraction has been defined as <1 cm/ hr cervical dilation for a minimum of 4 hours. In monitoring active labor, if hypotonic contractions are strongly suspected, internal monitors may be placed with amniotomy and again cervical change and contraction pattern are reassessed. Deficient Montevideo units and poor active labor progress typically prompts oxytocin augmentation.

9. Active-phase Arrest Handa and Laros (1993) diagnosed active-phase arrest, defined as no dilation for ≥2 hours, in 5 percent of term nulliparas. Inadequate uterine contractions, defined as <180 Montevideo units, were diagnosed in 80 percent of women with active-phase arrest Other criteria should also be met. First, the latent phase should be completed, and the cervix is dilated ≥4 cm. Also, a uterine contraction pattern of ≥200 Montevideo units in a 10-minute period has been present for ≥4 hours without cervical change

10. Obstetric Care Consensus Committee The first admonishes against cesarean delivery in the latent phase. Specifically, a prolonged latent phase should not be the sole indication for cesarean delivery. The second directive, too, is conventional practice. It recommends against cesarean delivery if labor is progressive but slow - a protraction disorder. A third instruction addresses the cervical dilation threshold that serves to herald active labor. Namely, a cervical dilation of 6 cm - not 4 cm - is now the recommended threshold. A fourth stipulation notes that cesarean delivery for active-phase arrest is best reserved for women with cervical dilation ≥6 cm and ruptured membranes who fail to progress despite 4 hours of adequate uterine activity or despite at least 6 hours of oxytocin administration but inadequate contractions.

11. The 6-cm rule for active labor derives from a slowing of the rate or flattening of the slope of cervical change in first-stage labor

12. Obstetric Care Consensus Committee The Consensus Committee suggests that cesarean deliveries for dystocia are being done before 6 cm cervical dilation. However, evidence suggests that all of the Committee’s first-stage recommendations are actually already empirically in use but are concurrent with an overall cesarean delivery rate 30 percent. Thus, Consensus Committee guidelines may fail to prevent additional cesareans for dystocia. Logically, further study is needed.

13. Second-stage Descent Disorders Fetal descent largely follows complete dilation. Moreover, the second stage incorporates many of the cardinal movements necessary for the fetus to negotiate the birth canal. Thus, disproportion of the fetus and pelvis frequently becomes apparent during second-stage labor. Similar to first-stage labor, time boundaries have been supported to limit second-stage duration to minimize adverse maternal and fetal outcomes. The second stage in nulliparas has been limited to 2 hours and extended to 3 hours when regional analgesia is used. For multiparas, 1 hour has been the limit, extended to 2 hours with regional analgesia.

14. Second-stage Descent Disorders Newer guidelines have been promoted by the Consensus Committee for second-stage labor. These recommend that a nullipara push for at least 3 hours and a multipara push for at least 2 hours before second-stage labor arrest is diagnosed. Importantly, one caveat is that maternal and fetal status should be reassuring. It is possible that prolonged first-stage labor presages that with the second stage.

15. Maternal Pushing Efforts With full cervical dilation, most women cannot resist the urge to push with uterine contractions. The combined force created by contractions of the uterus and abdominal musculature propels the fetus downward. However, at times, force created by abdominal musculature is compromised sufficiently to slow or even prevent spontaneous vaginal delivery. Heavy sedation or regional analgesia may reduce the reflex urge to push and may impair the ability to contract abdominal muscles sufficiently. Allowing time for these to abate is reasonable.

16. PRECIPITOUS LABOR AND DELIVERY Precipitous labor and delivery 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 a lack of pain with contractions to cue advanced labor. Precipitous labor terminates in expulsion of the fetus in <3 hours. Precipitous labor is frequently followed by uterine atony. Precipitous labors have been linked to cocaine abuse and associated with placental abruption, meconium, postpartum hemorrhage, and low Apgar scores

17. PRECIPITOUS LABOR AND DELIVERY For the neonate, adverse perinatal outcomes from rapid labor may be increased considerably for several reasons. The uterine contractions, often with negligible intervals of relaxation, prevent appropriate uterine blood flow and fetal oxygenation. Related to trauma, resistance of the birth canal rarely may cause intracranial injury. During unattended birth, the newborn may fall to the floor and be injured. Last, needed resuscitation may not be immediately available due to delivery speed. As treatment, analgesia is unlikely to modify these forceful contractions significantly. A single, intramuscular 250-ug terbutaline dose may be reasonable in an attempt to resolve a nonreassuring fetal heart rate pattern.

18. FETOPELVIC DISPROPORTION Pelvic Capacity: Fetopelvic disproportion arises from diminished pelvic capacity or from abnormal fetal size, structure, presentation, or position. Commonly, both are present. The pelvic inlet, midpelvis , or pelvic outlet may be contracted solely or in combination. Any contraction of the pelvic diameters that diminishes pelvic capacity can create dystocia.

19. Contracted Inlet Before labor, the fetal biparietal diameter averages from 9.5 to 9.8 cm. Thus, it might prove difficult or even impossible for some fetuses to pass through a pelvic inlet that has an anteroposterior diameter <10 cm. The anteroposterior diameter of the inlet is also called the obstetrical conjugate. It is commonly approximated by manually measuring the diagonal conjugate, which is approximately 1.5 cm greater. Inlet contraction usually is defined as a diagonal conjugate <11.5 cm.

20. Contracted Inlet Normally, cervical dilation is aided by hydrostatic action of the unruptured membranes or by direct application of the presenting part against the cervix after membrane rupture. In contracted pelves , however, because the head is arrested in the pelvic inlet, the entire force exerted by contractions acts directly on the portion of membranes that contact the dilating cervix. Consequently, early spontaneous rupture of the membranes is more likely. After membrane rupture, absent pressure by the head against the cervix and lower uterine segment predisposes to less effective contractions. Hence, further dilation may proceed very slowly or not at all. A contracted inlet also plays an important part in the production of abnormal presentations. In women with contracted pelves , face and shoulder presentations are encountered more frequently, and the cord prolapses more often.

21. Contracted Midpelvis This finding is more common than inlet contraction. It frequently causes transverse arrest of the fetal head, which potentially can lead to a difficult midforceps operation or to cesarean delivery. Average midpelvis measurements are as follows: transverse, or interischial spinous, 10.5 cm; anteroposterior, from the lower border of the symphysis pubis to the junction of S4 and S5, 11.5 cm; and posterior sagittal, from the midpoint of the interspinous line to the same point on the sacrum, 5 cm. The definition of midpelvic contractions has not been established with the same precision possible for inlet contractions. Even so, the midpelvis is likely contracted when the sum of the interspinous and posterior sagittal diameters of the midpelvis —normally, 10.5 plus 5 cm, or 15.5 cm—falls to 13.5 cm or less.

22. Contracted Outlet This finding usually is defined as an interischial tuberous diameter of 8 cm or less. Diminution of the intertuberous diameter with consequent narrowing of the anterior triangle must inevitably force the fetal head posteriorly. Outlet contraction without concomitant midplane contraction is rare. Although the disproportion between the fetal head and the pelvic outlet is not sufficiently great to give rise to severe dystocia, it may play an important part in perineal tears.

23. Pelvic Fractures fracture pattern, minor malalignment, and retained hardware are not absolute indications for cesarean delivery. In determining vaginal delivery candidates, fracture healing requires 8 to 12 weeks and thus recent fracture merits cesarean delivery. With a healed fracture, care includes review of pelvic radiographs and possible pelvimetry later in pregnancy.

24. Radiologic Assessment Current evaluation of pelvic capacity typically uses only digital interrogation of the bony pelvis. Of radiological methods, x-ray pelvimetry with cephalic presentations provides poor predictive value to diagnose CPD . Similarly, magnetic resonance pelvimetry fails to provide suitable accuracy in predicting cesarean delivery for dystocia. For fetal head size estimation, clinical and radiographical methods to predict CPD have proved disappointing.

25. Face Presentation Etiology and Diagnosis: With this presentation, the neck is hyperextended so that the occiput is in contact with the fetal back, and the chin (mentum) is presenting. The rate is approximately 0.1 percent of births. Causes of face presentations are numerous and include conditions that favor neck extension or prevent flexion. Preterm fetuses, with their smaller head dimensions, can engage before conversion to occiput presentation, and multifetal gestations carry increased risk. Face presentation is diagnosed by vaginal examination and palpation of facial features. Notably, a breech may be mistaken for a face presentation. Sonography can aid unclear cases.

26. Face Presentation Mechanism of Labor: Although some mentum posterior presentations persist, most convert spontaneously to an anterior position, even as late as second-stage labor. With the chin anterior, internal rotation of the face brings the chin under the symphysis pubis. Only in this way can the neck traverse the posterior surface of the symphysis pubis. After anterior rotation and descent, the chin and mouth appear at the vulva, and the undersurface of the chin presses against the symphysis. Instead, if the chin persists posteriorly, the relatively short neck cannot span the anterior surface of the sacrum. This position precludes the flexion necessary to negotiate the birth canal. Hence, vaginal birth from a mentum posterior position is impossible

27. Face Presentation Management: During labor, fetal heart rate monitoring is best done with external devices to help avoid face or eye injury. Because face presentations among term-size fetuses are more common with some degree of pelvic inlet contraction, cesarean delivery rates are substantially higher than with occiput presentation. If indicated, low or outlet forceps delivery of a mentum anterior face presentation can be completed. Vacuum extraction has been associated with eye trauma and is not recommended

28. Brow Presentation This uncommon presentation is diagnosed when that portion of the fetal head between the orbital ridge and the anterior fontanel presents at the pelvic inlet.

29. Brow Presentation Risks for persistent brow presentation mirror those for face presentation. A brow presentation is commonly unstable and converts to a face or an occiput presentation. The presentation may be recognized by abdominal palpation when both the occiput and chin can be palpated easily, but vaginal examination is usually necessary. Except when the fetal head is small or the pelvis is unusually large, engagement of the fetal head and subsequent delivery cannot take place as long as the brow presentation persists. Management principles mirror those for a face presentation.

30. Transverse Lie Etiology and Diagnosis With this, the fetus’ long axis lies approximately perpendicular to that of the mother. 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 position as right or left acromial. In addition, the back may be directed anteriorly or posteriorly and also superiorly or inferiorly. Thus, it is customary to further distinguish right or left varieties as dorsoanterior and dorsoposterior

31. Transverse Lie Some of the more common causes include abdominal wall relaxation from high parity, preterm fetus, placenta previa, abnormal uterine anatomy, hydramnios, and contracted maternal pelvis. A transverse lie is usually recognized easily, often by inspection alone. The abdomen is unusually wide, whereas the uterine fundus extends to only slightly above the umbilicus. During vaginal examination, in the early stages of labor, if the side of the thorax can be reached, the sequential parallel ribs are felt. With further dilation, the scapula and the clavicle are distinguished on opposite sides of the thorax.

32. Transverse Lie 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. With a neglected transverse lie, the uterus will eventually rupture. Even without this complication, maternal and fetal morbidity rates with transverse lie are increased because of the frequent association with placenta previa, umbilical cord prolapse, and fetal manipulations during cesarean delivery. If the fetus is small—usually <800 g—and the pelvis is large, spontaneous delivery is possible despite persistence of the abnormal lie.

33. Transverse Lie Management Active labor in a woman with a transverse lie typically requires cesarean delivery. With dorsoanterior or back down position, neither the fetal feet nor head occupies the lower uterine segment. A low transverse uterine incision may lead to difficult fetal extraction. Thus, a vertical hysterotomy incision is typically indicated. Before labor or early in labor, with the membranes intact, attempts at external cephalic version (ECV) are worthwhile. ECV success rates are high and exceed those for breech fetuses .

34. Umbilical Cord Prolapse Prolapse complicates 0.1 to 0.2 percent of births. umbilical cord prolapse may be more common with pelvis contraction. Most risks stem from an unengaged presenting part and include hydramnios, breech presentation, transverse lie, premature or small fetus with weight <2500 g, preterm rupture of membranes, and multifetal gestation. Umbilical cord prolapse is usually diagnosed clinically. The cord loop is palpated in a position lower in the vaginal canal than the head or beside it. For most cases, prompt manual elevation of the fetal head relieves cord compression. Concurrently, expeditious transfer to an operating room and preparations for cesarean delivery are completed.

35. Compound Presentation With this, an extremity prolapses alongside the presenting part, and both present simultaneously in the pelvis . In most cases, the prolapsed part should be left alone. It typically does not impede labor and often 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 part can be pushed gently upward and the head simultaneously downward by fundal pressure. In cases with a co-presenting hand, the fetus may reflexively retract the hand if pinched by the provider.

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