DIAGNOSISAND MANAGEMENT OF PLACENTA ACCRETA By Robert EDITOR’S NOTE: The occurrence of placenta accreta is unusual. However, when it occurs it can have a devastating efect on the patient. The ACOG Committee on Obstetric Practice has noted that the National Institute of Child Health and Human Dezlelopment has been paying increasing attention to this issue. As a result, the committee asked Dr. Robert Resnik to write an article on this subject. This article is being publithedin the ACOG Clinical Review to increase awareness of this obstetric complication. lacenta accreta occurs as a conseII) quence of a decidua basalis defect in which the anchoring placental villi are in direct contact with the myometrium rather than decidual cells. This adherent implantation leads to an incomplete separation of the placenta at the time of delivery and postpartum hemorrhage. Although the term placenta accreta is used commonly to describe the entire spectrum of invasive placentae, it refers specifically to superficial myometrial invasion. When deeper myometrial involvement or actual invasion of the trophoblast through the uterine serosal surface occur, the termsplacenta increta andplacentapercreta are used, respectively. Hemorrhage remains the third most common cause of maternal mortality in the United States. Placenta accreta has been reported to result in a 7% mortality rate, as well as intraoperative and postoperative morbidity, including massive blood transfusions, infection, ureteral ligation, and fistula formation.’ An abnormally adherent placenta is the most common indication for peripartal hysterectomy.1
INCIDENCE& RISK FACTORS The incidence of placenta accreta has changed notably from previous decades: 1930-1950, one in 30,739; 1950-1360, one in 19,012; 19601970, one in 14,780; and 1970-
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1980, one in 7270.? Actual cases probably are underreported. Data indicate that placenta accreta now occurs with a frequency of one in 2500 deliveries and appears to be an increasingly significant clinical problem because of high cesarean delivery rates during the last 15 years.4 The major risk factor for abnormal placental implantation is the combination of an anterior placenta previa with a uterine scar. When placenta previa is present without previous uterine surgery, the risk of accreta is l-5%. However, the risk increases sharply to as high as 300/o in women with a history of one cesarean delivery.5 Women who have had two or more cesarean deliveries with an anterior or central placental previa have a risk approaching 40%. Additional risk factors include previous myomectomy, endometrial defects secondary to vigorous curettage (Asherman syndrome), submucous leiomyomata, and maternal age 235 years.
DIAGNOSIS If a pregnancy is complicated by any of the aforementioned risk factors, diagnostic measures should be used, followed by a meticulous plan for delivery. The most useful diagnostic modalities appear to include abdominal and transvaginal ultrasound, colorflow Doppler, and magnetic resonance imaging (MRI). In the presence of anterior placenta previa, a normal placental attachment site is characterized by a hypoechoic boundary between the placenta and the urinary bladder. This hypoechoic line represents the myometrium and subplacental veins. Abnormal placental attachment is associated with focal or complete loss of the hypoechoic boundary, such that the echogenicity of the placenta appears to be contiguous with the bladder wall. Frequently, there are intraplacental sonolucent spaces with intense flow in the placenta adjacent to the uterine wall. Although there are few reported cases, it appears that presence of these abnormal ultrasound findings strongly sug\,‘,I1
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gests a diagnosis of placenta accreta, and their absence makes the diagnosis highly unlikely.“+8 Colorflow Doppler may reveal bloodflow in the base of the bladder in cases of placenta percreta.” The role of MRI remains undefined, but the test frequently confirms or rules out the diagnosis when uncertain ultrasound findings are present. An MRI also may be helpful in diagnosing accreta with a posterior placenta previa, in assessing deep myometrial or bladder involvement, and in determining parametrium involvement. It has not been shown consistently to help in delineating the difference between normal placentation and superficial invasion. It also has been reported that many women with placenta accreta will have an otherwise unexplained elevation in the maternal serum a-fetoprotein in the second trimester.‘O Accordingly, an elevated maternal serum a-fetoprotein in the second trimester and low-lying placenta with placenta previa should raise concerns about the possibility of accreta.
MANAGEMENT Because of the emergent nature of placenta accreta and the risk of lifethreatening hemorrhage associated with it, it is of great importance that obstetricians recognize its increasing frequency, risk factors, and diagnostic modalities. If there is a high index of suspicion for the diagnosis of placenta accreta, appropriate antenatal and intrapartum measures should be used to reduce the maternal mortality and morbidity risks. Prior to planned delivery, the patient should be counseled extensively about the likelihood that a cesarean hysterectomy may need to be performed. Adequate preparation should be made for the availability of blood and clotting factors, including the possibility of autologous blood if a diagnosis is made sufficiently early in pregnancy. In remote hospitals, or those with insufficient staff experience with this complication, it may be 1 ,, >.,
appropriate to consider patient transfer to a facility with an intensive care unit and extensive experience in dealing with potential intraoperative bleeding complications. If bleeding does not mandate delivery prior to 36 weeks’ gestation, fetal lung maturity should be determined, and if present, delivery may be scheduled at a time when ample personnel are available in the operating room and a sufficient supply of the patient’s blood type is available. The presence of an experienced pelvic surgeon is desirable in the event the hysterectomy requires wide excision due to parametrial involvement or partial resection of the bladder base. It is appropriate to plan a cesarean hysterectomy if risk factors and imaging findings are highly suggestive of this diagnosis, particularly if the patient does not wish continued fertility. The intraoperative problem of profuse hemorrhage develops when an attempt is made to remove the adherent placenta. When the decision has been made prior to surgery to perform a cesarean hysterectomy, the intact placenta is left in place following delivery of the fetus through a classical uterine incision. The uterine incision is closed, or oversewn circumferentially. A hysterectomy is then performed with meticulous attention to securing hemostasis. Vascular clips are helpful for control of bleeding at and below the uterine vessels. On occasion, an adherent placenta and postpartum hemorrhage are encountered at the time of vaginal delivery. If bleeding continues despite the usual conservative measures, the diagnosis of accreta must be considered. In this setting, hypogastric artery or selective pelvic vessel embolization may be an ideal alternative to hysterectomy. It has been suggested that balloon occlusion of the aorta or hypogastric vessels might help to prevent profuse blood loss during the hysterectomy and keep the operative site sufficiently dry to carry out a careful dissection. Preliminary reports, although few, show promising results in decreasing the amount of bleeding and maintaining a less bloody operative field.“~‘* Occlusion may be implemented for up to 15 minutes at a time, at appropriate intervals, without concern of ischemia to adjacent or disF!993 by Ihe American College of Obstetr!cians and Gweclllogsts Pubhkd by tlsewer Science Iill: 1066862199’% 00
tal tissues. This technique requires the availability of a skilled radiologistangiographer. An additional potential advantage of this technique is that the catheters may be used for embolization of small pelvic vessels if bleeding from the operative site persists postoperatively. A hypogastric artery ligation should not be considered because it is not effective in controlling pelvic hemorrhage in at least half the cases reported.‘3 Furthermore, hypogastric ligation precludes the subsequent use of angiographic embolization if needed to treat postoperative bleeding arising from the deep pelvic vessels. An alternative therapeutic modality that has been proposed involves a medical rather than a surgical approach. At the time of cesarean section, the uterine incision is closed and the placenta is left in place with the umbilical cord divided close to the fetal surface. Methotrexate is administered postoperatively. Rare successes have been reported, as well as significant hemorrhagic and infectious complications.‘*~‘s There is insufficient experience with methotrexate treatment of placenta accreta to recommend its use. The most important aspects of management of placenta accreta may be summarized as follows: l High index of suspicion based on risk factors; l Ultrasound diagnosis and possible confirmation by MRI; l Patient counseling regarding the risk of hemorrhage and cesarean hysterectomy; l Timed delivery with preparation including the support of the blood bank and availability of anesthetic and surgical expertise; l Cesarean hysterectomy performed with the placenta in place if all evidence points to a placenta accreta; l Diagnosis determined at the time of placental removal if antepartum diagnosis is uncertain and the patient wants to preserve fertility (planning should remain as outlined above and the patient should be informed that a hysterectomy may be required).
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REFERENCES 1. O’Brien JM, Barton JR, Donaldson ES. The management of placenta percreta: March/April
Conservative and operative strategies. Am J Obstet Gynecol 1996:175: 1632-8. Zelop CM, Harlow BL, Frigoletto FD Jr, Safon LE. Emergency peripartum hysterectomy. Am J Obstet Gynecol 1993;168:1443-8. Read JA, Cotton DB, Miller FC. Placenta accreta: Changing clinical aspects and outcome. Obstet Gynecol 1980; 56:31-4. Miller DA, Chollet JA, Goodwin TM. Clinical risk factors for placenta previa--Placenta accreta. Am J Obstet Gynecol 1997;177:210-4. Clark SL, Koonings PI’, Phelan JP. Placenta previa/accreta and prior cesarean section. Obstet Gynecol 1985;66:89 92. Finberg HJ, Williams JW. Placenta accreta: Prospective sonographic diagnosis in patients with placenta previa and prior cesarean section. J Ultrasound Med 1992;11:333-43. Levine D, Hulka CA, Ludmir J, Li W. Placenta accreta: E&ration with color Doppler US, power Doppler US, and MR imaging. Radiology 1997;205: 773-6. Kirkinen P, Helin-Martikainen HL, Vanninen R, Partanen K. Placenta accreta: Imaging by gray-scale and contrast-enhanced color Doppler sonography and magnetic resonance imaging. J Clin Ultrasound 199 8;26: 90. Lerner JP, Deane S, Timor-Tritsch IE. Characterization of placenta accreta using transvaginal sonography and color Doppler imaging. Ultrasound Obstet Gynecol 1995;5:198-201. Kupferminc MJ, Tamura IX, Wigton TR, Giassenberg R, Socol ML. Placenta accreta is associated with elevated maternaI serum alpha-fetoprotein. Obstet Gynecol 1993:82:266-Y. Dubois J, Garel L, Grignon A, LeMay M, Leduc L. Placenta percreta: BaIloon occlusion and embolization of the internal iliac arteries to reduce intraoperative blood losses. Am J Obstet Gynecol 1997;176:723-6. Paul1 JD, Smith J, Williams L, Davison G, Devine T, Holf M. Balloon occlusion of the abdominal aorta during caesarean hysterectomy for placenta percreta. Anaesth Intensive Care 19 9 5;23: 731-4. Clark SL, Phelan JP, Yeh SY, Bruce SR, Paul RH. Hypogastric artery ligation for obstetric hemorrhage. Obstet Gynecol 1985;66:353-6. Legro RS, Price FV, Hill LM, Caritis SN. Nonsurgical management of placenta percreta: A case report. Obstet Gynecol 1994;83:847-9. Jaffe R, DuBeshter B, Sherer DM, Thompson EA, Woods JR Jr. Failure of methotrexate treatment for term piacenta percreta. Am J Obstet Gynecol 1994; 171:558-Y.
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HISTORICAL PERSPECTIVE Continuedfrom p. 16 charge of obstetric anesthesia at Hopkins in 1959 -1960. During the years 1954-1967, Hustead taught residents how to modify Tuohy needles, which at that time were designed for continuous spinal anesthesia.8 He developed the Hustead Epidural Needle and the first epidural kits (with the Monoject engineers) at the University of Kansas in 1967. Douglas M. Goldsmith, DO, of Youngstown, Ohio, performed lumbar epidural anesthesia for obstetrics in the late 1950s and early 1960s at Detroit Osteopathic Hospital and at Youngstown Osteopathic Hospital.“ Epidural anesthesia had been in use sporadically at the Chicago Lying-In Hospital before 1966. In that year James Elam, MD, joined the faculty and organized a 24-hour obstetric anesthesia service with didactic teaching. Thereafter epidural anesthesia slowly was accepted by obstetricians. Obstetric epidural anesthesia was introduced at the University of Arkansas Medical Center in 1962 by a young obstetric resident, Paul Thompson.‘O Brett Gutsche, MD, performed the first lumbar epidural anesthesia for obstetrics at the University of Pennsylvania Hospital in 1969. Although epidural anesthesia had been used since the early 19OOs, it was not until the 1940s that it was recognized as a viable means of obstetric pain relief. Caudal anesthesia never became widely popular in the United States because of its technical diffculties and because it could not provide segmental anesthesia for the first stage of labor. Most institutions made the transition from heavy medication to epidural, general to epidural, or spinal to epidural without going through a cauda1 phase. Columbia-Presbyterian Medical Center was an exception. Epidural anesthesia succeeded because its use resulted in an awake, cooperative, pain-free mother and an alert infant. Epidural anesthesia became popular through evolution, rather than revolution. It superseded caudal anesthesia for several reasons: l The slight chance of hitting the fetal head was avoided l Segmental anesthesia was possible, preventing paralysis of the pelvic
including the levators, floor, which had led to posterior descent l Segmental analgesia with low concentration of local anesthetics and narcotics permitted maternal ambulation, if desired l Drug levels of local anesthetic were lower in mother and infant than they were with caudal anesthesia l Reductions in technical difficulty. The advent of plastic catheters stimulated the use of epidural anesthesia.
fessional service rendered. In the mid1970s Blue Cross reimbursement for any obstetric procedure was $15.00. As anesthesiologists, obstetricians, and patients clamored for appropriate financial reimbursement for their health insurance premiums from third-party carriers, higher reimbursement rates became the financial carrot to encourage hospitals to have anesthesiologists cover the obstetric suite.
OBSTACLES TO ACCEPTANCE
The popularity of epidural was sustained by a number of factors. First, the wide-spread use of electronic fetal monitoring in the 1970s allowed the obstetricians to be more comfortable with oxytocin stimulation. which they could now use liberally and safely. Flowers found oxytocin stimulation to be fundamental to the use of epidural anesthesia and used it in about 40% of cases. Second, the more liberal use of cesarean delivery made obstetricians less reluctant to administer an epidural in case of a less than perfect obstetric course. Whether epidural anesthesia slows labor or results in a higher cesarean delivery rate is still being debated. Third (and most importantlv) women want it, women demand it, and women receive it!
Obstetric anesthesia faced three crises in the 1950s and 1960s. The first came from the obstetricians, who initially resented another physician intruding on their relationship with their patients. This concern was lessened by the advent of the damagedbaby lawsuits-the obstetrician was glad to be relieved of the anesthetic responsibility and to have a fellow physician to defend the maternal anesthetic. In a more limited realm, several obstetricians wrote and spoke extensively about the danger to the mother and the fetus from regional anesthesia, especially spinal anesthesia, in preeclampsia. Concerns of professional infringement and maternal/fetal wellbeing were among the few areas of resistance to the use of lumbar epidural anesthesia. In most quarters epidural was accepted fairly readily as more anesthesiologists entered the field, fetal monitoring improved, epidural anesthesia was refined, and physicians became better informed. The second crisis for obstetric anesthesia came from the anesthesiologists. Initially there were too few anesthesiologists available for staff to spare a body for long-term periods of coverage in the obstetric suite. If obstetrics were covered, the operating room would be left short handed. Obviously, the operating room was the location where more income could be made for less effort and hassle. As anesthesia residents received more exposure to obstetric physiology and the science of regional anesthesia during the training, more individuals found the science and skill of obstetric anesthesia to be professionally satisfying. The third crisis revolved around financial reimbursement for the pro-
CHANGESIN MEDICINE ENSUREITS CONTINUEDFAVOR
ecognition should be given to the efforts of J. G. P. Cleland, MD, who laid the theoretical and practical groundwork for lumbar epidural anesthesia for obstetrics at McGill University and eventually at the University of Oregon. Born in British Columbia in 1898, he flew as a fighter pilot for the Royal Air Force in World War I. After the war he entered medical school at McGill and performed fellowships in surgery, obstetrics/gynecology. and experimental physiology. Working with John Tait, MD, he studied the vasomotor reflex of the spleen. He adapted this methodology to the reproductive system and studied the efferent and afferent nerve supply of the uterus in the dog, using its visceromotor reflex. He determined that painful impulses from the uterus enter the spinal cord at the level ofT,, andTlz .‘I Thereafter, Cleland used paravertebral, transsacral, and caudal blocks to obtund the pain oflabor and
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