Obstetrics and Gynecology Placenta Accreta Case File

Placenta Accreta Case File

Eugene C. Toy, MD, Patti Jayne Ross, MD, Benton Baker III, MD, John C. Jennings, MD

CASE 12

A 35-year-old G5P4 woman at 39 weeks’ gestation is undergoing a vaginal delivery. She has a history of previous myomectomy and one prior low-transverse cesarean delivery. She was counseled about the risks, benefits, and alternatives of vaginal birth after cesarean, and elected a trial of labor. She proceeded through a normal labor. The delivery of the baby is uneventful. The placenta does not deliver after 30 minutes, and a manual extraction of the placenta is undertaken. The placenta seems to be firmly adherent to the uterus.

» What is the most likely diagnosis?

» What is your next step in management for this patient?

ANSWER TO CASE 12:

Placenta Accreta                                                       

Summary: A 35-year-old G5P4 woman at term with a prior history of a myomectomy and cesarean delivery is undergoing a vaginal delivery. The retained placenta is firmly adherent to the uterus when there is an attempt at manual extraction.

• Most likely diagnosis: Placenta accreta.
• Next step in management for this patient: Hysterectomy.

ANALYSIS

Objectives

1. Know the risk factors for and the clinical diagnosis of placenta accreta.
2. Understand that hysterectomy is usually the best treatment for placenta accreta.

Considerations

This patient has had two previous uterine incisions, which increases the risk of placenta accreta. The placenta is noted to be very adherent to the uterus, which is the clinical definition of placenta accreta, although the histopathological diagnosis requires a defect of the decidua basalis layer. The usual management of true placental accreta is hysterectomy since attempts to remove a firmly attached placenta often lead to torrential hemorrhage and/ or maternal exsanguination. Conservative management of placenta accreta, such as removal of as much placenta as possible and packing the uterus, often leads to excess mortality as compared to immediate hysterectomy. Nevertheless, in the rare case of a younger patient who strongly desires more children, this option may be entertained.

APPROACH TO:

Placenta Accreta                                                   

DEFINITIONS

PLACENTA ACCRETA: Abnormal adherence of the placenta to the uterine wall due to an abnormality of the decidua basalis layer of the uterus. The placental villi are attached directly to the myometrium.

PLACENTA INCRETA: The abnormally implanted placenta penetrates into the myometrium.

PLACENTA PERCRETA: The abnormally implanted placenta penetrates entirely through the myometrium into the serosa. Often invasion into adjacent organs (eg, bladder, bowel) is noted.

CLINICAL APPROACH

Risk factors for placental adherence include low-lying placentation or placenta previa, prior cesarean delivery or uterine curettage, or prior myomectomy. Antepartum bleeding may occur, especially when associated with placenta previa (see also Cases 10 [previa] and 11 [abruption] for more common causes of antepartum hemorrhage). With complete placenta accreta, there may be no antepartum bleeding and only a retained placenta. Excessive traction on the cord may lead to uterine inversion. With a retained placenta, clinicians will usually attempt a manual extraction of the placenta, in an effort to find a cleavage plane between the placenta and the uterus (Nitabuch’s layer). With placenta accreta, no cleavage plane is found. Prompt puerperal hysterectomy is usually the optimal choice in this circumstance. Because the placenta is so firmly adherent, attempts to conserve the uterus, such as leaving the placenta in situ, curettage of the placenta or removing the placenta “piecemeal,” are often unsuccessful, and may lead to torrential hemorrhage and maternal exsanguination. Recent research has pointed out the importance of a multidisciplinary team approach when placenta accreta is known or is suspected prenatally to optimize perinatal outcomes.

Placenta accreta should be suspected in circumstances of placenta previa, particularly with a history of a prior cesarean delivery (Table 12– 1). The greater the number of prior cesareans in the face of current placenta previa, the higher the risk of accreta, exponentially. For example, a woman with three or more prior cesarean deliveries and a low-lying anterior placenta suggestive of partial previa or a known placenta previa has up to a 40% to 50% chance of having placenta accreta. Some practitioners advise performing ultrasound examinations to assess the placental location in those women who have had a prior cesarean delivery. Studies examining the accuracy of magnetic resonance imaging (MRI) to diagnose placenta accreta prior to delivery reveal a sensitivity of only 38%. When the placenta is anterior or low-lying in position, there is a greater risk of accreta. One caution is that a lowlying placenta or placenta previa diagnosed in the first/ second trimester typically resolves by the third trimester, as the lower uterine segment develops, a phenomenon known as trophotropism. When an antenatal diagnosis of placenta accreta/previa is suspected, a planned cesarean hysterectomy should be arranged prior to the onset of labor, preferably. In this instance, the infant is delivered between 34 and 35 weeks (after betamethasone administration, without amniocentesis to check fetal lung maturity indices) without disturbing the trophoblast implantation site, and the placenta is left in situ as the hysterectomy is performed immediately after delivery of the infant.

Table 12–1 • RISK FACTORS FOR PLACENTA ACCRETA

Placenta previa or low-lying—with or without prior uterine scar Prior cesarean scar or other uterine scar (eg, transmural myomectomy, metroplasty, resection of cornual ectopic)—with or without previa Cesarean scar implantation of gestational sac Prior uterine curettage Advanced maternal age IVF pregnancy Multifetal pregnancy Exponentially increasing risk with increasing number of prior cesareans and current placenta previa Prior Asherman syndrome Prior endometrial ablation Uterine leiomyomata Prior pelvic irradiation Smoking

CASE CORRELATION See also Case 3 (Uterine Inversion) as placenta accreta is a risk factor for uterine inversion.

COMPREHENSION QUESTIONS

12.1 A 33-year-old G3P2002 woman who had two prior cesareans is currently at 38 weeks’ gestation. She is noted to have a posterior placenta. On ultrasound, there is evidence of possible placenta accreta. The patient is counseled about the possible risk of need for hysterectomy. Which of the following is the most accurate statement?

A. Having two prior cesareans is associated with a 50% risk for placenta accreta.

B. Placenta accreta is associated with a defect in the myometrial layer of the uterus.

C. If the patient had gestational diabetes, the risk for placenta accreta would be even higher.

D. The posterior placenta may be associated with less of a risk for accreta than an anterior placenta.

12.2 A 25-year-old woman at 34 weeks’ gestation is noted to have a placenta previa, after she presented with vaginal bleeding and has undergone sonography. At 37 weeks, she has a scheduled cesarean. Upon cesarean section, bluish tissue densely adherent between the uterus and maternal bladder is noted. Which of the following is the most likely diagnosis?

A. Placenta accreta

B. Placenta melanoma

C. Placenta percreta

D. Placental polyp

12.3 A 29-year-old G1P0 woman at 39 weeks’ gestation delivered vaginally. Her placenta does not deliver easily. A manual extraction of the placenta is attempted and the placenta seems to be adherent to the uterus. A hysterectomy is contemplated, but the patient refuses due to strongly desiring more children. The cord is ligated with suture as high as possible. The patient is given the option of methotrexate therapy. Which of the following is the most likely complication after this intervention?

A. Coagulopathy

B. Utero-vaginal fistula

C. Infection

D. Malignant degeneration

12.4 A 32-year-old woman undergoes myomectomy for symptomatic uterine fibroids, all of which are subserosal. The endometrial cavity was not entered during the procedure. Which of the following statements is most likely to be correct regarding the risk of placental accreta?

A. Her risk of accreta is most likely to be increased due to the myomectomy.

B. Her risk of accreta is most likely to be decreased due to the myomectomy.

C. Her risk of accreta is most likely not affected by the myomectomy.

D. If the myomectomy incisions are anterior, then she has an increased risk of a placental polyp.

ANSWERS

12.1 D. Placenta accreta is more common with increasing number of cesareans and placenta previa. Three prior cesareans with placenta previa are associated with up to a 50% risk for placenta accreta, in which the decidua basalis layer is defective. It is the endometrial layer that is defective and not the myometrial layer. Nevertheless, the placenta may grow into the myometrium or even through the entire uterus to the serosa.

12.2 C. The blue tissue densely adherent between the uterus and bladder is very characteristic of percreta, where the placenta penetrates entirely through the myometrium to the serosa and adheres to the bladder. Hematuria may be present in this situation. These findings are not typically found with placenta accreta or polyps. Malignant melanoma can metastasize to the placenta, but this is much less common under these circumstances.

12.3 C. The best management of placenta accreta is hysterectomy due to the great risk of hemorrhage if the placenta is attempted to be removed. When the patient refuses hysterectomy, then ligation of the umbilical cord as high as possible and attempt at IV methotrexate therapy has been attempted with limited success. Other than hemorrhage, the other complication to be concerned about is infection. The necrosis of the placental tissue can be a nidus for infection.

12.4 C. In general, myomectomy incisions on the serosal (outside) surface of the uterus do not predispose to accreta because the endometrium is not disturbed. However, the risk of accreta is not decreased due to the myomectomy either. Placental polyps result from retained products after either a term pregnancy or incomplete abortion, and occur inside the uterus. Therefore, the location of the incisions for a myomectomy will not influence whether or not a patient develops polyps. Placental implantation over a submucosal uterine fibroid may increase the risk of focal accreta.

    CLINICAL PEARLS    

» The usual management of placenta accreta/previa (abnormal adherence of the placenta to the uterus) is prelabor cesarean hysterectomy around 34 to 35 weeks, after betamethasone administration (without amniocentesis for fetal lung maturity indices). » Placenta accreta is associated with a defect in the decidua basalis (Nitabuch’s) layer and a significant increase in maternal mortality risk » The risk of placenta accreta increases in a woman with a prior uterine incision and placenta previa. The greater the number of cesareans, the higher the risk of accreta, exponentially. » Low-lying or placenta previa diagnosed in the first/second trimester will often resolve later in pregnancy, so repeat sonography is required. » Expert prenatal sonography and MRI are required for prenatal suspicion of placenta accreta. » Multidisciplinary approach to prenatally suspected cases of morbidly adherent placentation is paramount for optimal perinatal outcomes— involving obstetrics, maternal-fetal medicine, gynecologic oncology, urology, radiology, vascular surgery, anesthesia, neonatology, blood bank, and/or intensive care specialists.

REFERENCES

American College of Obstetricians and Gynecologists. Postpartum hemorrhage. ACOG Practice Bulletin 76. Washington, DC; 2006. (Reaffirmed 2013.) 

American College of Obstetricians and Gynecologists. Placenta accreta. ACOG Committee Opinion 529. Washington, DC; 2012. 

Bailit JL, Grobman WA, Rice MM, et al. Morbidly adherent placenta treatments and outcomes. Obstet Gynecol. 2015;125:683-689. 

Cunningham FG, Leveno KJ, Bloom SL, et al. Obstetrical hemorrhage. In: Williams Obstetrics. 24th ed. New York, NY: McGraw-Hill; 2014:830-832. 

Eller AG, Bennett, MA, Sharshiner M, et al. Maternal morbidity in cases of placenta accreta managed by a multidisciplinary care team compared with standard obstetric care. Obstet Gynecol. 2011 February;117 (2 Pt 1):331-337. 

Eller AG, Porter TF, Soisson P, Silver RM. Optimal management strategies for placenta accreta. BJOG. 2009 April;116(5):648-654. Epub 2009 February 4. 

Kim M, Hyashi RH, Gambone JC. Obstetrical hemorrhage and puerperal sepsis. In: H acker NF, Gambone JC, Hobel CJ, eds. Essentials of Obstetrics and Gynecology. 5th ed. Philadelphia, PA: Saunders; 2009:128-138. 

Robinson BK, Grobman WA. Effectiveness of timing strategies for delivery of individuals with placenta previa and accreta. Obstet Gynecol. 2010 October;116(4):835-842. 

Silver RM, Fox KA, Barton JR, et al. Center of excellence for placenta accreta. Am J Obstet Gynecol. 2015:561-567. 

Silver RM, Landon MB, Rouse DJ, et al. National Institute of Child Health and Human Development Maternal– Fetal Medicine Units Network. Maternal morbidity associated with multiple repeat cesarean deliveries. Obstet Gynecol. 2006 June;107(6):1226-1232. 

Warshak CR, Ramos GA, Eskander R, et al. Effect of predelivery diagnosis in 99 consecutive cases of placenta accreta. Obstet Gynecol. 2010 January;115(1):65-69.

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