Abnormal Presentation and Multiple Gestation




Abstract


The labor and delivery of a parturient with a multiple gestation and/or fetal breech presentation represents a major challenge for the obstetrician and the anesthesia provider. Anesthetic requirements may change from moment to moment, and an obstetric emergency may necessitate immediate intervention. All members of the perinatal care team must communicate directly and clearly with each other as well as with the parturient and her family to ensure the best possible outcome for both the mother and the neonate(s).




Keywords

Breech presentation, Face presentation, Abnormal position, External cephalic version, Breech extraction, Multiple gestation, Twin vaginal birth

 






  • Chapter Outline



  • Abnormal Position, 822



  • Breech Presentation, 823




    • Epidemiology, 823



    • Obstetric Complications, 824



    • Obstetric Management, 825



    • Anesthetic Management, 829




  • Other Abnormal Presentations, 830




    • Face Presentation, 830



    • Brow Presentation, 830



    • Compound Presentation, 830



    • Shoulder Presentation, 830




  • Multiple Gestation, 831




    • Epidemiology, 831



    • Placentation, 831



    • Physiologic Changes, 831



    • Obstetric Complications, 832



    • Obstetric Management, 834



    • Anesthetic Management, 835



The labor and delivery of a parturient with a multiple gestation and/or fetal breech presentation represents a major challenge for the obstetrician and the anesthesia provider. Anesthetic requirements may change from moment to moment, and an obstetric emergency may necessitate immediate intervention. All members of the perinatal care team must communicate directly and clearly with each other as well as with the parturient and her family to ensure the best possible outcome for both the mother and the neonate(s).


The presentation denotes that portion of the fetus that overlies the pelvic inlet. In most cases, the fetal presenting part can be palpated through the cervix during a vaginal examination. The presentation may be cephalic, breech, or shoulder. Breech and shoulder presentations occur with increased frequency in patients with multiple gestation. Cephalic presentations are further subdivided into vertex, brow, and face presentations according to the degree of flexion of the neck. With an asynclitic presentation, the fetal head is tilted toward one shoulder and the opposite parietal eminence enters the pelvic inlet first.


The lie refers to the alignment of the fetal spine with the maternal spine. The fetal lie can be either longitudinal or transverse. A fetus with a vertex or breech presentation has a longitudinal lie. A persistent oblique or transverse lie typically requires cesarean delivery.


The position of the fetus denotes the relationship of a specific fetal bony point to the maternal pelvis. The position of the occiput defines the position for vertex presentations ( Fig. 34.1 ). Other markers for position are the sacrum for breech presentations, the mentum for face presentations, and the acromion for shoulder presentations. The attitude of the fetus describes the relationship of the fetal parts with one another; the term is typically used to refer to the position of the head with regard to the trunk, as in flexed, military, or hyperextended.




Fig. 34.1


Fetal head position in the maternal pelvis. OA, occiput anterior; LOA, left occiput anterior; LOT, left occiput transverse; LOP, left occiput posterior; OP, occiput posterior; ROP, right occiput posterior; ROT, right occiput transverse; ROA, right occiput anterior.




Abnormal Position


During normal labor, the fetal occiput rotates to a direct occiput anterior position (see Fig. 34.1 ). In a minority of patients with a right or left occiput posterior position, the occiput rotates directly posteriorly and results in a persistent occiput posterior position. The occiput posterior position may lead to a prolonged labor that is associated with increased maternal discomfort. Less often, the vertex remains in the occiput transverse position; this condition is known as deep transverse arrest. Obstetricians diagnose fetal head position with ultrasonography or palpation of the sagittal suture during vaginal examination.


Obstetricians may perform manual or forceps rotation to hasten delivery and lessen perineal trauma in women with an abnormal position of the vertex. Today, many obstetricians are reluctant to perform rotational forceps delivery for fear of causing excessive maternal and/or fetal trauma; however, manual rotation of the vertex is often attempted as obstetricians work to facilitate vaginal birth. Some cases of persistent occiput posterior position, and many cases of deep transverse arrest, require cesarean delivery because of dystocia.


During administration of epidural analgesia to a patient with an abnormal position, the addition of a lipid-soluble opioid to a dilute solution of local anesthetic is particularly useful. This combination provides analgesia while preserving pelvic muscle tone. Relaxation of the pelvic floor and perineum may prevent the spontaneous rotation of the vertex during labor. In contrast, profound pelvic floor relaxation is needed to facilitate instrumental vaginal delivery with forceps.




Breech Presentation


Breech presentation describes a longitudinal lie in which the fetal buttocks and/or lower extremities overlie the pelvic inlet. Fig. 34.2 shows the three varieties of breech presentation:




  • Frank breech— lower extremities flexed at the hips and extended at the knees



  • Complete breech— lower extremities flexed at both the hips and the knees



  • Incomplete breech— one or both of the lower extremities extended at the hips




Fig. 34.2


Three possible breech presentations. (A) The complete breech demonstrates flexion of the hips and flexion of the knees. (B) The incomplete breech demonstrates intermediate deflexion of one or both hips and knees. (C) The frank breech shows flexion of the hips and extension of both knees.

(From Lanni SM, Gherman R, Gonik B. Malpresentations. In Gabbe SG, Niebyl JR, Simpson JL, et al., eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:368–394.)


Ultrasonographic or radiographic examination typically allows the obstetrician to confirm the type of breech presentation and to exclude the presence of associated severe congenital anomalies (e.g., anencephaly). The type of breech presentation may influence the obstetrician’s decision regarding the mode of delivery. The fetus with a frank breech presentation tends to remain in that presentation throughout labor. In contrast, a complete breech presentation may change to an incomplete breech presentation at any time before or during labor.


Epidemiology


The breech presentation is the most common of the abnormal presentations. Both the incidence and the type of breech presentation vary with gestational age ( Table 34.1 ). Before 28 weeks’ gestation, approximately 25% of fetuses are in a breech presentation. Most change to a vertex presentation by 34 weeks’ gestation, but 3% to 4% of fetuses remain in a breech presentation at term.



TABLE 34.1

Types of Breech Presentation




















Type of Breech Percentage of All Breech Presentations Percentage of Preterm Gestation Breech Presentations
Frank 48–73 38
Complete 5–12 12
Incomplete 12–38 50

Modified from Lanni SM, Gherman R, Gonik B. Malpresentations. In Gabbe SG, Niebyl JR, Simpson JL, et al. eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:376.


Many factors predispose to breech presentation ( Box 34.1 ). Abnormalities of the fetus or the maternal pelvis or uterus may play a role. Among patients with pelvic or uterine abnormalities, a breech presentation may allow more room for fetal growth and movement. Likewise, hydrocephalic fetuses are more likely to assume a breech presentation. Multiparity, multiple gestation, polyhydramnios, and anencephaly also predispose to breech presentation. These conditions may interfere with the normal process of accommodation between the fetal head and the uterine cavity and maternal pelvis.



Box 34.1

Factors Associated With Breech Presentation


Uterine Distention or Relaxation





  • Multiparity



  • Multiple gestation



  • Polyhydramnios



  • Macrosomia



Abnormalities of the Uterus or Pelvis





  • Pelvic tumors



  • Uterine anomalies



  • Pelvic contracture



Abnormalities of the Fetus





  • Hydrocephalus



  • Anencephaly



Obstetric Conditions





  • Previous breech delivery



  • Preterm gestation



  • Oligohydramnios



  • Cornual-fundal placenta



  • Placenta previa



Modified from Cunningham FG, Leveno KJ, Bloom SL, et al. eds. Williams Obstetrics. 24th ed. New York, NY: McGraw-Hill Education; 2014:558–573; Lanni SM, Gherman R, Gonik B: Malpresentations. In Gabbe SG, Niebyl JR, Simpson JL, et al. eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:368–394.


Obstetric Complications


Obstetric complications are more likely with a breech presentation ( Table 34.2 ). Cesarean delivery decreases the risk for some of these complications. Vaginal breech delivery entails a higher risk for neonatal trauma than delivery of an infant with a vertex presentation, but cesarean delivery does not eliminate the risk for trauma to the infant. Rather, cesarean delivery of a breech presentation can be difficult and traumatic, especially if the skin and uterine incisions are insufficient or maternal muscle relaxation is inadequate.



TABLE 34.2

Incidence of Complications Associated With Breech Presentation





































Complication Incidence
Intrapartum fetal death Increased 16-fold a
Intrapartum asphyxia Increased 3.8-fold a
Umbilical cord prolapse Increased 5- to 20-fold a
Birth trauma Increased 13-fold a
Arrest of aftercoming head 4.6%–8.8%
Spinal cord injuries with deflexion 21%
Major congenital anomalies 6%–18%
Preterm delivery 16%–33%
Hyperextension of head 5%
Fetal heart rate abnormalities 15.2%

Modified from Lanni SM, Gherman R, Gonik B. Malpresentations. In Gabbe SG, Niebyl JR, Simpson JL, et al. eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:381.

a Compared with cephalic presentation.



The risk for umbilical cord prolapse varies with the type of breech presentation ( Table 34.3 ). In the parturient with an incomplete breech presentation, the presenting part does not fill the cervix as well as the vertex or buttocks, allowing the umbilical cord to prolapse into the vagina before delivery. Umbilical cord prolapse typically necessitates emergency cesarean delivery.



TABLE 34.3

Risk for Umbilical Cord Prolapse
















Type of Breech Risk for Cord Prolapse (%)
Frank 0.5
Complete 4–6
Incomplete 15–18

Modified from Lanni SM, Gherman R, Gonik B: Malpresentations. In Gabbe SG, Niebyl JR, Simpson JL, et al. eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:376.


Morbidity and Mortality


There is a higher risk for perinatal morbidity and mortality with a breech presentation, even when the risk is adjusted for preterm gestation. The factors that cause breech presentation are often more important than the presentation itself. For example, the severe congenital anomalies that predispose to breech presentation (e.g., hydrocephalus, anencephaly) significantly contribute to neonatal morbidity and mortality. Relative perinatal mortality rates (calculated from data for linked siblings from the Medical Birth Registry of Norway) confirm that breech presentation is a marker of perinatal risk, regardless of the mode of delivery. Even after successful external cephalic version (ECV), women are at increased risk for cesarean delivery due to dystocia or an abnormal fetal heart rate (FHR) tracing, as compared with women presenting with a cephalic presentation.


Vaginal breech delivery entails a higher risk for maternal morbidity (e.g., infection, perineal trauma, hemorrhage) than vertex delivery. However, among women with a fetal breech presentation, maternal outcomes are similar between women who had a planned cesarean delivery and those who had a trial of labor. At 2 years postpartum, maternal morbidity assessed by questionnaire (917 responses for a 79% return) was not different for urinary incontinence, breast-feeding, pain, depression, menstrual problems, fatigue, and distressing memories of the birth experience. In a single-center study of 846 singleton breech deliveries, Schiff et al. also did not find a higher risk for maternal morbidity in women who underwent cesarean delivery during labor than in women who underwent planned cesarean delivery.


Obstetric Management


External Cephalic Version


The process of ECV converts a breech or shoulder presentation to a vertex presentation. The average success rate for this procedure is 58%, with a wide range reported in published studies. ECV is most likely to be successful if (1) the presenting part has not entered the pelvis, (2) amniotic fluid volume is normal, (3) the fetal back is not positioned posteriorly, (4) the patient is not obese, (5) the patient is parous, and (6) the presentation is either frank breech or transverse. Early labor does not preclude successful ECV, but ECV is rarely successful when the cervix is fully dilated or when the membranes have ruptured. No scoring system has been developed that reliably predicts which candidates will have a successful version attempt, although the variables just listed can be used when obtaining informed consent.


The optimal timing of ECV is after 36 or 37 weeks’ gestation, for the following reasons. First, if spontaneous version to a vertex presentation is going to occur, it will likely happen by 36 or 37 weeks’ gestation, and successful performance of ECV after 37 weeks’ gestation decreases the likelihood of reversion from a vertex to a breech presentation. Second, if complications occur during ECV performed after 37 weeks’ gestation, emergency delivery will not result in delivery of a preterm infant.


Successful ECV helps reduce the risk for perinatal morbidity and mortality associated with breech delivery. The American College of Obstetricians and Gynecologists (ACOG) has suggested that “because the risk for an adverse event occurring as a result of external cephalic version is small and the cesarean delivery rate is significantly lower among women who have undergone successful version, all women near term with breech presentations should be offered an ECV attempt if there are no contraindications.” There is no general consensus on eligibility for ECV, and contraindications vary between published guidelines. Oligohydramnios may be the most common contraindication cited. Labor and vaginal delivery occur in the majority of patients who have undergone successful ECV, but anesthesia providers should remain vigilant because of the increased risk for intrapartum cesarean delivery necessitated by dystocia or a nonreassuring FHR tracing.


ECV is associated with a low rate of morbidity in contemporary obstetric practice, although placental abruption and preterm labor have been reported. Safe ECV requires FHR monitoring and access to cesarean delivery services. In a systematic review of 84 studies that involved 12,955 women, complications included transient (6.1%) and persistent (0.22%) FHR abnormalities, vaginal bleeding (0.30%), placental abruption (0.08%), emergency cesarean delivery (0.35%), and stillbirth (0.19%). Fetal-maternal hemorrhage is another potential complication of ECV. In one study, 16 of 89 (18%) patients undergoing ECV had Kleihauer-Betke stains that signaled the occurrence of fetal-maternal hemorrhage.


Obstetricians usually administer a tocolytic agent (e.g., terbutaline or nitroglycerin) before performing ECV. A randomized placebo-controlled trial found that the success rate of version was doubled when terbutaline was given rather than placebo. A randomized controlled trial of intravenous nitroglycerin for tocolysis (100- to 300-µg bolus doses, up to a maximum total dose of 1000 µg) found that the success rate was 24% in nulliparous women who received nitroglycerin versus 8% in the placebo group. The success rate was higher in parous women (43%), but it did not differ between the nitroglycerin and placebo groups. Interestingly, the rates of hypotension were similar between groups. A Cochrane Review found that tocolytic therapy with a beta-adrenergic agonist drug for ECV increases the number of women with a cephalic presentation at the onset of labor (relative risk [RR], 1.68; 95% confidence interval [CI], 1.14 to 2.48) and reduces the number of cesarean deliveries (RR, 0.77; 95% CI, 0.67 to 0.88).


Another method to improve the success rate of ECV may be use of neuraxial analgesia or anesthesia. Several studies have described the use of epidural or spinal analgesia or anesthesia for ECV. For example, Weiniger et al. randomly assigned 70 nulliparous women to receive either spinal anesthesia with bupivacaine 7.5 mg or no anesthesia for ECV. The success rate was 67% in those receiving spinal anesthesia, 32% in those without analgesia, and 42% in those who did not consent to enroll in the study. A randomized controlled trial in parous women using similar methodology also found an increased success rate with spinal anesthesia (87% versus 58%). A meta-analysis of 9 trials and 934 women found that compared with control, neuraxial anesthesia increased ECV success rates, increased the occurrence of cephalic presentation in labor, increased vaginal delivery rates, decreased cesarean delivery rates, and decreased maternal discomfort. There was no difference in the incidence of emergency cesarean delivery, transient fetal bradycardia, nonreassuring fetal testing, or placental abruption.


Maternal discomfort may be significant during ECV; greater pain during the procedure is associated with a lower chance of success. Some obstetricians argue that the absence of anesthesia limits the force that the obstetrician can apply during the procedure. They contend that administration of anesthesia may encourage the obstetrician to use excessive force, possibly increasing the risk for perinatal morbidity and mortality, but that concern is not supported by published evidence. In fact, spinal anesthesia reduces the force required for successful version.


Several investigators have reported successful outcomes with neuraxial analgesia or anesthesia in women in whom the first attempt at ECV without neuraxial analgesia had been unsuccessful. These patients elected to undergo another version attempt with neuraxial analgesia. Weiniger et al. found that failure of ECV was attributed to pain in 15 women in their control group. Eleven of those 15 (73%) women subsequently had successful ECV with spinal analgesia.


The optimal dose of spinal local anesthetic is controversial. A meta-analysis of seven studies using neuraxial blockade to facilitate ECV concluded that administration of an anesthetic dose of local anesthetic doubles the success rate of ECV (RR, 1.95; 95% CI, 1.46 to 2.60), whereas an analgesic dose does not have any effect (RR, 1.18; 95% CI, 0.94 to 1.49). A subsequent prospective, randomized, blinded trial addressed the question of optimal intrathecal bupivacaine dose to facilitate ECV success. Patients were randomized to receive intrathecal bupivacaine doses of 2.5, 5.0, 7.5 or 10.0 mg combined with fentanyl 15 µg as part of a combined spinal-epidural technique. Overall success rate of ECV was 51.5% with no difference in success rates or cesarean delivery rates between the groups, demonstrating that intrathecal bupivacaine doses greater than 2.5 mg are not necessary and may only increase the incidence of hypotension. Obstetricians did not perceive a difference in abdominal wall relaxation between the groups, even though pain scores were higher in the 2.5 mg bupivacaine group (12 versus 4 to 5 on a 0 to 100 scale). Patient satisfaction was high and not different between groups. In an accompanying editorial, Carvalho and Bateman suggested that the optimal dose varies according to the clinical situation. If the goal is timely discharge whether or not the version is successful, then a lower-dose spinal anesthetic will allow earlier discharge as a result of faster resolution of the block. If the patient will be admitted for delivery regardless of whether the version is successful, then a higher dose will not affect the patient’s length of admission and could facilitate emergent cesarean delivery should that become necessary.


In contrast to neuraxial analgesia or anesthesia, intravenous analgesia does not appear to facilitate successful ECV. Khaw et al. randomized parturients to receive either spinal anesthesia with intrathecal hyperbaric bupivacaine 9 mg plus fentanyl 15 µg, intravenous analgesia using a remifentanil infusion at 0.1 µg/kg/min, or control (no anesthetic or analgesic intervention) before attempted ECV. On the first attempt, success rates were 83% in the spinal group versus 64% in the remifentanil group and 64% in the control group. Among those that failed, a second attempt was successful in 78% of the patients with spinal anesthesia versus 0% receiving remifentanil. There was no significant difference in fetal bradycardia requiring cesarean delivery.


In our practice, we provide spinal or combined spinal-epidural anesthesia during ECV at patient or obstetrician request. Evidence suggests that neuraxial anesthesia may help facilitate successful version and vaginal delivery, and therefore it should be used routinely. If a neuraxial technique is used, intrathecal administration of 2.5 mg bupivacaine combined with fentanyl may provide optimal conditions. Higher local anesthetic doses may be appropriate if delivery is planned for the admission, but may increase the incidence of hypotension.


Mode of Delivery


A substantial number of obstetricians recommend the routine performance of cesarean delivery in patients with a breech presentation. The publication of the Term Breech Trial in 2000 changed clinical practice around the world. In contemporary obstetric practice in the United States, most parturients with a breech presentation are delivered by cesarean.


The Term Breech Trial Collaborative Group enrolled 2088 women from 26 countries with a singleton fetus in a frank or complete breech presentation. These women were randomly assigned to undergo planned cesarean delivery or planned vaginal delivery. Using an intent-to-treat analysis, the investigators noted that perinatal and neonatal mortality rates, and serious neonatal morbidity, were significantly lower in the planned cesarean delivery group (1.6% versus 5%). This difference was greatest in those countries with a low perinatal mortality rate (e.g., Canada, United Kingdom, United States). Secondary analysis of perinatal outcomes demonstrated that the lowest risk for adverse outcome occurred when a prelabor cesarean delivery was performed at term gestation. The risk for adverse perinatal outcome progressively increased with cesarean delivery performed during early labor and active labor and was highest with a vaginal birth. Labor augmentation and a longer time between the start of pushing and delivery were associated with an increased risk for adverse perinatal outcome, whereas the presence of an experienced clinician at delivery was associated with a reduced risk for adverse perinatal outcome.


In the Term Breech Trial, maternal morbidity and mortality did not differ between the two groups for the first 6 postpartum weeks. Women who underwent planned cesarean delivery were less likely to report urinary incontinence at 3 months ; however, there was no difference at 2 years. As assessed by questionnaire, maternal outcomes at 2 years after delivery were similar after planned abdominal delivery and after planned vaginal delivery for singleton breech infants born at term.


Despite the results of the Term Breech Trial, Canadian multicenter data from 2003 to 2011 illustrate that vaginal delivery was increasingly popular for Canadian women with breech presentation of nonanomalous singleton infants at term. The vaginal delivery rate increased from 2.7% to 3.9% over that time, and the rate of cesarean deliveries in labor increased from 8.75% to 9.8%. Delivery by planned cesarean had the lowest morbidity. Composite neonatal morbidity and mortality rates were significantly higher after vaginal delivery than planned cesarean with an adjusted rate ratio of 3.6 (95% CI, 2.50 to 5.15). Cesarean delivery during labor also resulted in higher neonatal morbidity and mortality. The Canadian data support the results of the Term Breech Trial.


In many other regions of the world, the number of planned vaginal breech deliveries has decreased as a result of the Term Breech Trial. For example, in Denmark, the proportion of singleton term breech infants delivered vaginally decreased abruptly from 20% before 1999 to 6% after 2001. At the same time, intrapartum or early neonatal mortality among all term breech infants decreased from 0.13% to 0.05% (RR, 0.38; 95% CI, 0.15 to 0.98). The downward trend in rates of vaginal breech delivery is likely to continue. As the number of practitioners with experience in performing vaginal breech delivery has decreased, the number of vaginal breech deliveries available to teach obstetric residents may no longer be adequate. Unintended results of this practice change include a generation of obstetricians who have lost the skills to practice vaginal breech deliveries and medicolegal concerns that now discourage the practice of vaginal breech delivery.


Nevertheless, obstetricians in some regions of the world retain a strong tradition of offering vaginal breech delivery for selected patients. Published in 2006, the PREsentation et MODe d ‘Accouchement (PREMODA; presentation and mode of delivery) study described birth outcomes for all term breech deliveries in 2001 through 2002 in 174 centers in France and Belgium. The study included 5579 women who planned cesarean breech delivery and 2526 women who planned vaginal breech delivery, of whom 1796 actually delivered vaginally. The primary outcome captured a composite of fetal and neonatal mortality and serious morbidity and was not different between women who planned to undergo vaginal delivery (1.60%; 95% CI, 1.14 to 2.17) and women who planned to undergo cesarean delivery (1.45%; 95% CI, 1.16 to 1.81), with an overall odds ratio (OR) of 1.10 (95% CI, 0.75 to 1.61). The authors suggested that rigorous adherence to protocols for patient selection, intrapartum fetal surveillance, and second-stage management contributed to improved outcomes for women attempting vaginal breech delivery.


In 2006, in recognition of results from the PREMODA study and other single-center descriptions of excellent outcomes for vaginal breech delivery, the ACOG made the following recommendations about mode of singleton breech delivery at term:




  • “The decision regarding the mode of delivery should depend on the experience of the health care provider. Cesarean delivery will be the preferred mode of delivery for most physicians because of the diminishing expertise in vaginal breech delivery.”



  • “Obstetricians should offer and perform external cephalic version whenever possible.”



  • “Planned vaginal delivery of a term singleton breech fetus may be reasonable under hospital-specific protocol guidelines for both eligibility and labor management.”



  • “In those instances in which breech vaginal deliveries are pursued, great caution should be exercised, and detailed patient informed consent should be documented.”



  • “Before embarking on a plan for a vaginal breech delivery, women should be informed that the risk of perinatal or neonatal mortality or short-term serious neonatal morbidity may be higher than if a cesarean delivery is planned.”



Although a planned trial of labor and vaginal breech delivery occurs uncommonly in most hospitals in North America and the United Kingdom because of concerns for higher rates of adverse perinatal outcomes, vaginal breech delivery still occurs because some patients present in advanced labor. Selection criteria such as those listed in Box 34.2 are used by advocates of a trial of labor and vaginal delivery. The availability of personnel experienced in obstetric anesthesia and neonatal resuscitation are prerequisites for a trial of labor. Hyperextension of the fetal head remains an absolute contraindication to a trial of labor in the patient with a breech presentation.


Jun 12, 2019 | Posted by in ANESTHESIA | Comments Off on Abnormal Presentation and Multiple Gestation
Premium Wordpress Themes by UFO Themes