NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA, AND CORD ACCIDENTS pot

403 BREECH PRESENTATION DEFINITIONS, ASSOCIATIONS, INCIDENCES, AND IMPORTANCE Breech is a longitudinal presentation in which the cephalic pole oc- cupies the fundus and the caudal (podalic) pole lies in the lower segment of the uterine cavity or within the birth canal. Overall breech presentation occurs in 3%–4% of singleton pregnancies com- mencing labor, but has a much higher incidence in multiple gestations (e.g., ϳ25% of first twins and ϳ50% of second twins are breech). The incidence rises further in higher order multiple pregnancies. Other associations with breech presentation include: earlier gestations (35% at Ͻ28 weeks, 25% at 28–32 weeks, 20% at 32–34 weeks, 8% at 34–35 weeks, 2%–3% at Ͼ36 weeks), a prior breech (over 4-fold increase after one and up to 30-fold after three), placental placement (i.e., placenta previa), oligohydramnios, fetal congenital anomalies (e.g., hydrocephalus), pelvic tumors imping- ing on the uterus or birth canal (e.g., leiomyomata), and uterine anomalies (e.g., bicornuate, septate uterus). As presentations are thought to be a matter of fetal–uterine ac- commodation, breech presentation may be caused by any aberration of this adaptive process or of the fetal attitude. Thus, breech presentation is not a disease or an abnormality. However, breech presentation may be an important sign of congenital fetal compromise. For example, breech presentation is increased with chromosomal anomalies (e.g., trisomies 18 and 21), neuromuscular abnormalities (e.g., familial dysautonomia), and skeletal malformations (e.g., spina bifida, meningomyelocele). The incidence of major congenital anomalies 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA, AND CORD ACCIDENTS CHAPTER Copyright 2001 The McGraw-Hill Companies. Click Here for Terms of Use. BENSON & PERNOLL’S 404 HANDBOOK OF OBSTETRICS AND GYNECOLOGY (e.g., anaencephaly, hydrocephaly) in breech presentations is more than double (ϳ6%) that found in vertex. Additionally, delivery of the breech fetus imposes perinatal risks of birth anoxia and birth trauma as well as maternal risks of traumatic delivery, or cesarean section. There are three types of breech presentation (Fig. 14-1): frank (legs flexed at the hip and extended at the knee), complete (legs flexed at the hip and flexed at the knee), and footling (legs extended at the hip and extended at the knee). The amount of both hip and knee extension in footling breech is variable and may involve one FIGURE 14-1. The three types of breech presentation. (single footling) or both (double footling) feet as the presenting part. The incidence of frank breech increases as size increases (40% Ͻ2500 g, 65% over 2500 g), whereas complete breech represents ϳ10% at all sizes and footling breech decreases in relation to size (50% Ͻ2500 g, 25% Ͼ2500 g). In breech presentations (all three types), the fetal reference point to describe position and station is the sacrum. Knowledge of the type of breech presentation is es- sential to management. DIAGNOSIS Physical examination is generally the first clue to breech presentations. Leopold’s maneuvers discover the softer and less well-defined breech above the pelvic inlet and the firm, well-defined head in the uterine fundus. The fetal heart (heard best over the back) is found higher on the maternal abdomen. Vaginal examination (with cervical dilatation) reveals the softer and irregular breech presentation, a foot, or feet as opposed to the usually encountered firm, smooth, rounded cephalic presentation with readily identified sutures. The diagnosis is usually confirmed by sonography. Sonography is also useful to determine multiple gestation, the type of breech, attitude, size (and gestational age), location of the placenta, and amniotic fluid volume. Given the incidence of congenital anomalies (Ͼ6%) associated with breech presentation, an anatomic survey is also helpful. If the sonography has been accomplished at some time prior to labor, it is useful to repeat the ul- trasound at the onset or early in labor to confirm fetal presentation, head position, and to estimate fetal size. Radiography is rarely necessary. MANAGEMENT PRENATAL Confirmation, Follow-up, and Counseling Given current utilization of sonography during pregnancy, breech presentations are usually detected in the second trimester. However, some breech presentations remain undetected prior to the onset of labor. A recent report from a large managed care program indicated that ϳ21% of term breeches were not detected before the onset of labor and an additional 15% not detected until after 38 weeks of gestation. On those that are detected earlier, follow up sonography (often ϳ32 weeks and ϳ36 weeks) is useful to ascertain if the usual CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA 405 BENSON & PERNOLL’S 406 HANDBOOK OF OBSTETRICS AND GYNECOLOGY course of spontaneous version to vertex occurs, to determine fetal size and attitude, and to screen for fetal defects. Breech patients are considered at risk and their care plans are customarily individualized and more rigorous than vertex, low-risk patients. When breech presentation persists, parental involvement is en- couraged. This usually involves dissemination of information, counseling concerning the presentation, detailing available management options, and discussion of the parent’s concerns and ques- tions. The goal of this counseling is to formulate a plan for delivery that meets the parents’ desires, can be executed by the health care provider(s), and affords maximal safety for both mother and child. Patients with breech presentations are warned to come to the hospital as soon as labor begins or spontaneous rupture of membranes occurs. The latter is particularly important because of the increased incidence of cord prolapse. As noted previously, admission sonography is necessary. External Cephalic Version External cephalic version (ECV) is the term describing maneuvers performed through the maternal abdominal wall attempting to con- vert the presentation from breech to vertex (Fig. 14-2). Antenatally, ECV is limited to singleton gestations and is usually performed after the 36th week, but prior to the onset of labor. Although ECV has been performed as early as the 28th week of gestation, early attempts are currently less favored because of a high recurrence to breech and to avoid preterm delivery if complications occur. ECV is more successful in: multigravidas, pregnancies with sufficient amniotic fluid, and in unengaged complete and footling breech presentations. ECV is contraindicated by: prior uterine sur- gery (myomectomy, cesarean section or metroplasty), suspected or documented congenital malformations, indications of fetal compromise (e.g., intrauterine growth retardation, abnormal biophysi- cal testing), placenta previa, anterior placentation (i.e., placenta between the fetus and the abdominal wall), abruptio placenta, premature rupture of the membranes, marked oligohydramnios, and engagement of the presenting part. Relative contraindications include those conditions limiting the use of tocolytic agents (maternal cardiac disease, diabetes mellitus, or thyroid disorders) and frank breech (the lower extremities act as a splint, preventing flexion). ECV should only be performed in a facility with proper equip- ment and staffing for emergency cesarean. One commonly used rou- tine follows. Obtain informed consent. The patient should inform the operator if pain occurs or if the maneuvers seem too forceful. Sonographically verify presentation, flexion of the fetal head, appropriateness of size, and adequacy of amniotic fluid. If not previously performed, rule out fetal congenital anomalies and uterine abnormalities. A nonstress test is conducted and must be reactive to proceed. A Kleihauer-Betke test is drawn to rule out fetomaternal hemorrhage. Determine if the uterus is sufficiently relaxed to allow the procedure without tocolysis. Although uterine tone may be the most important predictor of success when selecting candidates for ECV, other useful criteria are uterine irritability and contractions. If further relaxation is necessary administer ritodrine hy- drochloride, 0.15 mg/min IV for 15 min. Analgesics and anes- thetics are not generally used. Using both hands on the patient’s abdomen, gently “disengage” the fetal lower pole by moving it toward the fundus as well as laterally toward the fetal back. Simultaneously, pressure is ex- erted on the fetal head downward and contralateral to the CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA 407 FIGURE 14-2. External cephalic version demonstrating an alternative to the successful “forward roll.” BENSON & PERNOLL’S 408 HANDBOOK OF OBSTETRICS AND GYNECOLOGY direction of the lower pole. In sum, this is positioning the fetus in a forward roll. If that is unsuccessful, a back flip may be attempted. If unsuccessful, the ECV may be reattempted at a later time. Sonographic or electronic fetal monitoring is used during and after to monitor fetal well-being and ascertain the success of ECV. Following ECV, the nonstress test and Kleihauer-Betke tests are repeated. Signs of fetal compromise (e.g., electronic fetal monitoring criteria, fetomaternal hemorrhage) are treated accord- ingly (usually immediate cesarean) and if the Kleihauer-Betke is positive and the mother is Rh-negative, Rh immune globulin is given to prevent sensititization. In the absence of worrisome findings in this screening, the spontaneous onset of labor is routinely monitored by outpatient care. The overall success of ECV is reported to be as high as 66%, with 33%–50% success for nullipara and 45%–75% success for multiparas. Although successful ECVs may return to breech prior to delivery, this generally happens in Ͻ10%. Women with successful ECV have approximately the same cesarean rate as those with primary cephalic presentations. Although ECV may afford the individual patient the opportunity for a cephalic vaginal delivery, it would reduce overall cesarean rates by only ϳ1% if universally applied. Complications of ECV also include: intrauterine fetal demise secondary to umbilical cord entanglement (Ͻ1%), emergency cesarean (Ͻ1%), abruptio placenta, premature rupture of membranes, preterm labor, umbilical cord prolapse, fetomaternal hemorrhage, and uterine rupture. Planned Vaginal Delivery Health providers contemplating a vaginal breech delivery must be both trained as well as experienced in the process and procedure. Adequate support must be available, including: an experienced obstetrician to assist with delivery, and anesthesiologist and a pediatrician capable of providing total resuscitation and care of the newborn. Anesthesia is usually kept to a minimum, although epidural anesthesia has proven useful. The additional support personnel (e.g., nursing, respiratory therapy) and facilities must be prepared to deal with these patients as part of a comprehensive team. Factors predisposing to fetal injury during labor and delivery of a breech presentation include: greater incidence of umbilical cord prolapse, a higher incidence of cord compromise during labor, increased incidence of placental separation, entrapment of the head by the cervix, injury to the head and neck by more rapid descent through the birth canal, injury of the head and neck by the mode of delivery, and a greater chance of injury to the upper extremities. Thus, attempting vaginal delivery is usually reserved for patients meeting rather stringent criteria (Table 14-1). Using such criteria, 10%–15% of all candidates will meet the criteria. Of those, ϳ70% will deliver vaginally, but nulliparas are only ϳ50% likely to succeed whereas ϳ75% of multiparas will be delivered vaginally. The most common indications for cesarean section are labor disorders or nonreassuring fetal heart rate patterns. Recently, induction of labor in patients with a breech presentation and an unripe cervix using proglandin ripening has been reported to be efficacious (vaginal delivery of ϳ50%) and safe. The use of oxytocin for labor abnormalities remains controversial. CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA 409 TABLE 14-1 CRITERIA FOR ATTEMPTING VAGINAL DELIVERY Fetal criteria Frank breech presentations (although selected cases of complete or footling breech are considered in certain centers) Gestational age of Ն34 weeks Estimated fetal weight of 2000–3500 g Flexed fetal head Maternal criteria Informed consent Adequate maternal pelvis (many authorities believe this should be obtained by x-ray pelvimetry, whereas others believe a clinical evaluation is sufficient; data are inadequate to indicate this improves perinatal outcomes) Absence of maternal contraindications to labor Absence of maternal or fetal indications for cesarean section Special circumstances Presentation in advanced labor with no fetal or maternal compromise; a controlled vaginal delivery may be safer in these circumstances than a hastily executed cesarean section Previable fetus Lethal fetal congenital anomalies BENSON & PERNOLL’S 410 HANDBOOK OF OBSTETRICS AND GYNECOLOGY Umbilical cord blood acid–base values for uncomplicated, term, vaginal breech deliveries differ significantly from those of uncomplicated cephalic vaginal delivery. The differences suggest a greater degree of acute cord compression with vaginal breech delivery. This suggestion is furthered by breech vaginal deliveries (compared to elective cesarean) having a greater risk of low Apgar scores (as high as 15-fold more). Additionally, there are significantly more neonatal intensive care admissions for vaginal breech deliveries (Ͼ1.5-fold). Planned Cesarean Section Delivery Given the risks of cord prolapse with rupture of the membranes, as well as the risks of early labor, most planned cesarean deliveries are electively scheduled at Ն38th week. One set of criteria for these cases follows (Table 14-2). Singleton breech cesarean deliveries have lower birth weight- specific neonatal morbidity and mortality compared to vaginal births. Approximately 30% of patients anticipating a vaginal delivery will have cesarean section delivery for signs of fetal compromise or abnormalities of labor. INTRAPARTUM TABLE 14-2 CRITERIA FOR PLANNED CESAREAN SECTION DELIVERY Fetal criteria Estimate fetal weight of Ͼ3500 g Deflexed fetal head Prolonged rupture of membranes Unengaged presenting part Premature fetus (gestation of 25–34 weeks) Most complete or footling breech presentations Ͼ25 weeks without detectable lethal congenital anomalies Variable heart rate deceleration on electronic monitoring Maternal criteria Informed consent Contracted or borderline pelvic capacity Elderly primigravida Infertility problems or poor obstetric history Dysfunctional labor As noted previously, patients with breech presentations should come to the hospital as soon as possible when rupture of the membranes or labor occurs. A repeat sonography is accomplished with specific attention to position, attitude, and location of fetal extremities. A full history and physical examination are accomplished. Pelvic examination is conducted, with specific attention to station and whether cord is presenting or palpable. Fetal monitoring is performed and fetal well being assessed. Reappraisal of the mode of delivery is performed. The preparations necessary for delivery are conducted (see above). If a vaginal delivery is anticipated, the screening for fetopelvic disproportion is reassessed and the necessary preparations for vaginal and cesarean delivery are conducted. Continuous monitoring is performed to screen for fetal compromise. Labor’s progress is care- fully evaluated by monitoring dilatation and descent of the presenting part. Artificial rupture of the membranes is avoided until the presenting part is well applied. At the time of membrane rupture, the patient is examined vaginally to check for potential cord prolapse. As little analgesia and anesthesia as possible is used, with epidural anesthesia being the choice should mild analgesia and lo- cal anesthesia not be adequate. Abnormalities of labor are regarded for their potential indication of cesarean section necessity. The second stage of labor is interfered with as little as possible. DELIVERY Cesarean Section The cesarean incision is chosen to be as atraumatic to the fetus as possible. A vertical incision in the lower uterine segment (which frequently extends into the lower fundus) is chosen when the presenting part is higher in the uterus, if there is an indication that the fetus will require more room for delivery, and for many premature deliveries. A transverse lower uterine segment incision is performed when the lower uterine segment is well developed, the presenting part is well down in the uterus, and there are no special fetal re- quirements. Once the uterus is opened, the breech is delivered by total breech extraction (see below). If most expeditious, the fetus is grasped (as with vaginal delivery) over the hips with the thumbs on the sacrum and the fetus gently extracted at a moderate rate. In some cases, delivery is facilitated by first delivering the legs. This may be accomplished by either directly grasping the feet or by flexing the knees to facilitate grasping and delivering the feet. At the level of the shoulders, the arms are swept out of the uterus by pressure CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA 411 BENSON & PERNOLL’S 412 HANDBOOK OF OBSTETRICS AND GYNECOLOGY along the anterior portion of the humerus. Care is taken not to overextend the neck. Gentle pressure on the uterus (by the assistant) immediately above the head, while the obstetrician supports the body, facilitates delivery of the head. The cord is immediately clamped. Vaginal Delivery of the Breech Presentation Vaginal delivery is facilitated by: a generous episiotomy, allowing the fetus to be expelled to the level of the umbilicus before manip- ulation, loosening and drawing down a short loop of cord when the umbilicus come through the introitus, and having the assistant support the body while the head is being delivered. Delivery of the Body There are three methods for breech delivery of the body. Total breech extraction involves grasping both of the lower extremities initially, and then the pelvis when it is available, to literally extract the fetus from the uterus and birth canal. This is the most hazardous method of vaginal delivery. Spontaneous expulsion is simply allowing full delivery of the body without manipulative interference and is intermediate in fetal hazard. The safest vaginal breech delivery is assisted breech delivery. In this case, the fetus is spontaneously expelled to the level of the umbilicus and the remainder of the fetus is extracted by gentle pressure on the pelvis with the obstetrician’s thumbs over the sacrum. While an assistant supports the body, the obstetrician rotates the fetus as it descends so that the spine is in the midline directly under the symphysis pubis. Gentle downward pressure on the pelvis brings both scapulas under the symphysis. Rotation of the body brings the right shoulder beneath the pubic symphysis. The operator (using the right hand) locates the right humerus and exerts gentle pressure on the anterior surface until the arm is delivered. The left arm is likewise delivered (Fig. 14-3). Delivery of the Head (Figs. 14-4 and 14-5) As the body is rotated back to the mid position, delivery of the head is commenced. During this time, fundal pressure by an assistant keeps the head flexed and the body is gently lifted upward. Usu- ally the head delivers spontaneously over the perineum. When as- sistance for delivery of the head in breech births is necessary, it can be accomplished manually or with forceps. The Mauriceau-Smellie- Veit maneuver involves the obstetrician placing the index and mid- dle finger of one hand over the maxilla as the body rests of the fore- arm. Two fingers of the operator’s other hand are applied on either side of the neck with gentle traction. As the body is elevated, this allows controlled delivery of the mouth, nose, and brow. [...]... (5%), and frank breech (0.5%) OVERT CORD PROLAPSE The incidence of overt cord prolapse with singleton gestations has been variously reported from 0.1%–0.5% About 50% of cases occur with breech presentations, and another 10% with transverse presentations, whereas 40% occur with vertex presentations Nearly two thirds of overt cord prolapse occurs in multiparas Due to increased instability and malpresentations,... pressure ap- CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA 419 plied by an assistant as the head delivers and maximally flexing the maternal legs at the hips (McRoberts maneuver) In unavoidable cases, management requires clinical judgment and individualized care Time is of the essence The fetus is at risk of asphyxiation, because it cannot expand the chest to breathe and umbilical cord circulation... sterile gloved hand is used to put pressure upward on the presenting part to relieve cord compression Attempts at cord reposition are nearly fruitless, but the cord is palpated for viability and fetal heart tones are monitored continuously Oxygen is administered to the mother Delivery is accomplished as quickly as possible The mode of delivery depends CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA... Umbilical cord prolapse Occult and forelying cords occur with intact membranes, while complete cord prolapse occurs with membrane rupture 422 BENSON & PERNOLL’S HANDBOOK OF OBSTETRICS AND GYNECOLOGY on the cervical dilatation, but nearly all will be delivered by cesarean section Perinatal mortality, even in modern centers, exceeds 35% and morbidity of survivors is variously reported OCCULT CORD PROLAPSE... vagina and over the vulva after the membranes rupture When the cord is first compressed, there may be violent fetal activity The cord may be seen or palpated and the fetal heart tones will reflect cord compromise More than 15% of these patients present with an intrauterine fetal demise These cases are managed conservatively by allowing delivery to proceed When the fetus is viable and there is complete cord. .. deliveries 4500–4750 g, and 21.1% (34.8% with diabetes) of deliveries 4750–5000 g Shoulder dystocia is increased by more than a third in vacuum or forceps assisted births (to between 4.6%–45%) If the fetus is Ͼ4000 g, and there is a prolonged second stage and midpelvic intrumentation, shoulder dystocia has been reported to be as high as 23% Conditions that create larger and/ or more rigid shoulders or fetal... all cord prolapses) and still higher with higher order multiple gestations Overt cord prolapse occurs more frequently with low birth weight infants, in contrast to occult prolapse of the cord When the cord is presenting, it may be palpated through the membranes if there is cervical dilatation Complete prolapse of the umbilical cord is associated with rupture of the membranes The patient may feel the cord. .. their increased risk with attempting vaginal birth UMBILICAL CORD PROLAPSE Cord prolapse occurs when the presenting part does not fill the lower uterine segment and impinge on the cervix (Fig 14-7) This allows the cord to enter this space and lie alongside (occult) or lower (overt) than the presenting part The overt form is far more serious and is highly associated with malpresentation, as reflected... delivers and remains near transverse, the final phase of external rotation (the head reassuming the position it originally emerged) does not occur; the chin is tightly applied to the perineum and the face become progressively cyanotic The anterior shoulder is impacted behind the symphysis pubis and the posterior shoulder is lodged against the bony pelvis at an angle precluding further descent Although shoulder. ..CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA FIGURE 14-3 Assisted breech delivery of the fetal body 413 414 BENSON & PERNOLL’S HANDBOOK OF OBSTETRICS AND GYNECOLOGY FIGURE 14-4 Initial operator and assistant positioning for the MauriceauSmellie-Veit maneuver Piper forceps, the second method of assisted . anomalies 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA, AND CORD ACCIDENTS CHAPTER Copyright 2001 The McGraw-Hill Companies. Click Here for Terms of Use. BENSON & PERNOLL’S 404 HANDBOOK OF OBSTETRICS AND GYNECOLOGY (e.g.,. depends CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA 421 FIGURE 14-7. Umbilical cord prolapse. Occult and forelying cords occur with intact membranes, while complete cord prolapse occurs. mouth, nose, and brow. CHAPTER 14 NONVERTEX PRESENTATIONS, SHOULDER DYSTOCIA 413 FIGURE 14-3. Assisted breech delivery of the fetal body. BENSON & PERNOLL’S 414 HANDBOOK OF OBSTETRICS AND GYNECOLOGY Piper

Định dạng
Số trang	20
Dung lượng	357,23 KB