The Role of Interventional Radiology in the Management of the Difficult Cesarean Delivery
Joanna Kee-Sampson
Travis E. Meyer
Daniel Siragusa
INTRODUCTION AND HISTORICAL PERSPECTIVES
Endovascular interventions performed by interventional radiologists for high-risk obstetric cases can decrease morbidity and mortality in the peripartum period. In the interest of best maternal outcomes, the management of high-pregnancies should include interventional radiology as a key member of the multidisciplinary team.
The father of modern interventional radiology, Charles Dotter, published a seminal article in 1963 describing the recanalization of an artery through a small hole in the artery,1 without the need to perform surgery. With refinement in transarterial techniques and advances in equipment over the years, the scope of interventional radiologists has expanded to include an increasing range of procedures for an ever-widening range of indications.2 Transarterial techniques are particularly suited to halt or prevent bleeding in any organ system because they are minimally invasive and highly effective. The first case of transcatheter embolization for an obstetric indication was published in 1979,3 describing the case of a 22-year-old with massive postpartum hemorrhage after vaginal delivery which was inadequately controlled by packing, hysterectomy, and bilateral internal iliac artery ligation. Embolization of the left internal pudendal artery was eventually performed by an interventional radiologist, which succeeded at stabilizing the patient.
Transarterial techniques are now used for a number of obstetric and gynecologic indications including abnormal placentation, menorrhagia, and postpartum hemorrhage or postpartum bleeding.4 In this chapter, we will describe the obstetric indications for transarterial therapy and include a discussion on the infrastructure and set-up for the treatment, management, and predelivery planning of high-risk pregnancies by the obstetrics-interventional radiology team.
PREDISPOSING CONDITIONS TO PERIPARTUM HEMORRHAGE
Placenta Accreta Spectrum
The decidua basalis layer of the placenta prevents abnormal adherence of the placenta to the myometrium and enables placental separation during labor. Placenta accreta, morbidly adherent placenta, and abnormal placental implantation are terminologies that were used in reference to the abnormal adherence of the placenta to the
myometrium from ingrowth of the chorionic villi through the decidua basalis. Placenta accreta spectrum is the updated terminology for this pathology. The depth of chorionic villi invasion characterizes the severity of the placental abnormality and is classically described as placenta accreta, increta, and percreta denoting chorionic invasion not invading, partially invading, and full-thickness invasion of the myometrium beyond the serosa. In placenta percreta, the abnormal placenta may adhere to the surrounding abdominopelvic organs and musculature. After delivery, when the abnormal placenta does not separate from the uterus, postpartum hemorrhage may occur, potentially leading to hemorrhagic shock, coagulopathy, hysterectomy, and death.5 Women with placenta accreta spectrum on average lose 3 to 5 L of blood at delivery, and 40% require transfusion of more than 10 units of packed red blood cells. Maternal mortality has been reported at 7%.6,7
myometrium from ingrowth of the chorionic villi through the decidua basalis. Placenta accreta spectrum is the updated terminology for this pathology. The depth of chorionic villi invasion characterizes the severity of the placental abnormality and is classically described as placenta accreta, increta, and percreta denoting chorionic invasion not invading, partially invading, and full-thickness invasion of the myometrium beyond the serosa. In placenta percreta, the abnormal placenta may adhere to the surrounding abdominopelvic organs and musculature. After delivery, when the abnormal placenta does not separate from the uterus, postpartum hemorrhage may occur, potentially leading to hemorrhagic shock, coagulopathy, hysterectomy, and death.5 Women with placenta accreta spectrum on average lose 3 to 5 L of blood at delivery, and 40% require transfusion of more than 10 units of packed red blood cells. Maternal mortality has been reported at 7%.6,7
Incidence and Risk Factors for Placenta Accreta Spectrum
The incidence of placenta accreta spectrum has progressively increased from 1:4027 pregnancies in the 1970s to 1:533 pregnancies from 1982-2002, to 1:272 pregnancies in 2016.8,9 This dramatic increase has mainly been attributed to the increase in the rates of cesarean section, which now exceeds 30% in developed countries.5,10 Furthermore, the incidence of placenta accreta spectrum increases with the incidence of placenta previa, which has also been strongly correlated with a history of prior cesarean section. In any individual woman, the larger the number of previous cesarean sections, the greater the risk of abnormal placental implantation, increasing from a risk of 3.3% in a woman without prior cesarean sections to 67% in those with four or more prior cesarean sections.5,8 Other minor risk factors that predispose to the development of placenta accreta spectrum are advanced maternal age, multiparity, prior uterine surgery, and endometrial curettage.
Diagnosis of Placenta Accreta Spectrum
Ultrasound
Screening for placenta accreta spectrum occurs at the routine 18 to 20 week ultrasound examination, with extra care at imaging the anterior myometrium and bladder should the patient have any relevant history that would increase the risk of developing placenta accreta spectrum.11 The reported sensitivity and specificity of sonography in the diagnosis of placenta accreta spectrum were 91% and 97%, respectively, in a systematic review and meta-analysis.12 The absence of relevant sonographic findings, however, should not preclude a diagnosis of placenta accreta spectrum as clinical risk factors are equally important predictors.8
The normal sonographic appearance of the placenta-myometrium junction should show a thin hypoechoic line separating the placenta from the inner myometrium. The subplacental blood flow pattern should be organized and parallel the myometrium.11 As previously discussed, placenta previa is a risk factor for developing placenta accreta spectrum. When placenta previa is seen on ultrasound examination, careful additional imaging with color Doppler and transvaginal probes should be performed to exclude concurrent placenta accreta. Other abnormal findings seen in placenta accreta spectrum are placental lacunae, increased vascularity around the uterus, irregular bladder wall, absence of the retroplacental clear space, and anterior myometrial thickness less than 1 mm.11,13
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is indicated when there are risk factors for placenta accreta spectrum but ultrasound findings are equivocal, when there is a posterior placenta previa, or to assess the depth of myometrial invasion in percreta.8,11,13 MRI is also a useful adjunctive imaging tool in the preoperative planning of cesarean section delivery and peripartum hysterectomy.13 The sensitivity and specificity of MRI in the diagnosis of placenta accreta spectrum are comparable to sonography; however, it is more expensive, not as widely available, and requires more expertise for interpretation, and therefore, it is not recommended as a first-line imaging modality for placenta accreta spectrum.8
MRI findings seen in an invasive placenta are uterine bulging, heterogeneity of the placenta with increased vascularity, and dark bands in the placenta extending from the myometrium, and in later pregnancy, focal myometrial interruptions may be seen (Figure 12-1). In placenta percreta, the placenta may invade the surrounding organs and structures.11 The administration of gadolinium-based contrast may improve the delineation of the placenta-myometrium junction; however, its use during pregnancy is controversial because of its ability to cross the placenta and circulate in the amniotic fluid. The effects of gadolinium on the fetus are unknown. The American College of Radiology Manual on Contrast Media recommends that gadolinium-based contrast medium should be administered with caution to pregnant women and only when the potential significant benefits outweigh the possible but unknown risks to the fetus.14
 FIGURE 12-1 Sagittal magnetic resonance imaging (MRI) of a 32-year-old woman with placenta previa and accreta. The placenta (yellow arrow) is covering the cervical os (white arrow). There is also loss of the normal uterus-placental hypointense zone, consistent with placenta accreta. |
Uterine Atony
Uterine atony is the failure of the uterus to contract after delivery. It is the most common cause of peripartum hemorrhage.15 Uterotonic agents should be the first treatment for abnormal postpartum hemorrhage due to uterine atony according to the American College of Obstetricians and Gynecologists (ACOG) guidelines, based on good and consistent scientific evidence (level A).16 When manual uterine massage and uterotonic medications fail to adequately control the blood loss, prompt surgical or transarterial intervention is warranted.
Although hysterectomy remains the most definitive solution, it is also more invasive than alternatives and of course removes the option for future pregnancies. Uterine or internal iliac artery ligation via laparoscopic approaches can minimize recovery times but are also considered more invasive than transarterial embolization. Bilateral internal iliac artery ligation has success rates of 40% to 100%, while bilateral uterine artery ligation has success rates of approximately 92%.17 Transarterial embolization of the uterine arteries has reported success rates of approximately 85% to 100%.18,19,20 In locations where interventional radiology is not readily available, laparoscopic ligation is an important option. In cases where embolization fails, laparoscopy may be pursued before complete hysterectomy; however, if ligation has been performed first, then embolization can be very technically difficult with lower success rates leaving hysterectomy as the only remaining option.21
Genital Lacerations
Perineal and genital tract lacerations can occur in up to 80% of deliveries.22 Common sites for laceration include the perineum and vagina but can also occur on the labia, clitoris, urethra, and cervix. The severity of lacerations varies from minor lacerations that affect the skin or superficial structures of the perineum to more severe lacerations that damage the muscles of the anal sphincter complex and rectum. Risk factors for more severe lacerations include induced labor, epidural anesthesia, increased birth weight of the infant, and operative or augmented vaginal delivery.23
For mild lacerations, no intervention is usually required. For moderate lacerations, approximation of the tissue with absorbable suture and packing of the vagina is often sufficient.24 In cases of significant hemorrhage or where suturing does not control blood loss, interventional or operative management is the next step.
Postpartum genital tract lacerations often involve the vaginal artery which is a branch of the anterior division of the internal iliac artery. Selective embolization with Gelfoam or coils can provide excellent control of the hemorrhage.25 As with all pelvic embolizations, a postembolization pelvic angiogram at the level of L3-L4 is warranted to exclude alternative sources of bleeding not previously identified before removing arterial access.26 In cases where active extravasation is not identified, empiric embolization of the bilateral uterine arteries can be performed depending on the location of the laceration. Temporary embolization of the internal iliac artery on the side of the laceration is acceptable if arterial ligation or hysterectomy is the only competing alternative in the setting of unidentified hemorrhage.
DELIVERY PLANNING AND DELIVERY
Facility and Multidisciplinary Team
Because of the risk of massive peripartum hemorrhage and associated morbidities, the American College of Obstetricians and Gynecologists strongly recommends (grade 1B) that perinatal care in a patient with placenta accreta spectrum should take place in a facility capable of level III or IV maternal care where there is adequate blood bank, personnel, and medical subspecialty support and experience.8 The availability of a multidisciplinary team consisting of in-house obstetrician gynecologists, gynecologic oncologists, anesthesiologists, other surgical subspecialties, and immediate availability of interventional radiologists are essential to providing the best maternal outcomes. In a retrospective cohort study of deliveries complicated by placenta accreta spectrum, women who delivered in a medical center with a multidisciplinary care team had a greater than 50% risk reduction of early morbidity compared with those who delivered in a less equipped medical center.27
Planned Versus Emergency Cesarean Hysterectomy
Generally, a planned cesarean delivery is preferred over an emergency cesarean hysterectomy as this leads to better outcomes.5,8 The timing of planned delivery should be tailored to each patient’s circumstance, taking into consideration clinical stability and the degree of placental invasion. Some authors prefer to deliver at 34 weeks for the best maternal and fetal outcomes.5,28 The ACOG recommends scheduled delivery between 34 0/7 to 35 6/7 weeks of gestation in a stable patient.8 The standard of care is cesarean hysterectomy at the time of delivery, but newer, uterus-conserving techniques have been described to preserve fertility in select patients.5,8
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