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4.2.5 Placenta Accreta Syndromes

Morbidly Adherent Placentas

  • Accreta: villi are attached to the myometrium
  • Increta: villi invade the myometrium
  • Percreta: penetrate through the myometrium and to/through the serosa

Risk Factors

  • Similar risk factors for placenta previa
  • Associated placenta previa
  • Prior cesarean delivery
  • Prior endometrial curettage or ablation (myometrial damage)
  • Elevated human chorionic gonadotropin (hCG) screening
  • Full thickness myomectomy may result in an accreta in non-traditional anatomic locations

Clinical Pearl

History is key! If there is an anterior placenta previa the risk for accreta is 3% for para 0 patients, but once they have had a C/S and an anterior previa, the risk rises quite quickly: 15% after 1 section, 40% after 2 sections. So keep a high index of suspicion in patients with anterior previa and prior C/S. If there is any chance that the previous hysterotomy scar was covered by the placenta – refer on for work up of placenta accreta. The diagnosis is challenging even for seasoned radiologists.

Placenta Accreta Syndromes (PAS)

A. Placenta Accreta:

B. Placenta Increta

C. Placenta Percreta

Identification of Placenta Accreta Syndromes

Placenta accreta spectrum disorders in the setting of prior Caesarean section deliveries arises from pregnancy implantation within the niche created by this surgery near the cervicoisthmic junction of the uterus. This early presentation as a “Caesarean section scar pregnancy” may be diagnosed by ultrasound methods.

Sonography can be useful for antepartum identification of abnormal ingrowth:

  • Small myometrial thickness in 1st trimester, loss of normal hypoechoic retroplacental zone, placental vascular lacunae, placental bulging into the posterior bladder wall.
  • Doppler colour flow mapping can help predict myometrial invasion.

If MRI is available, it can be helpful to outline anatomy and to identify invasion into adjacent structures, however utility is limited by relative contraindication of gadolinium contrast in pregnancy.

Pre-operative management of PAS

Pregnant women with clinical risk factors for placenta accreta spectrum disorders and anterior placenta previa at the 18–20-week fetal anatomical ultrasound should be referred for specialist imaging to diagnose or exclude this disorder.

Involves major decisions regarding timing and the ideal facility for delivery:

  • Women with a diagnosis of placenta accreta spectrum disorder should be referred to a regional centre dedicated to the interdisciplinary management of this condition.
  • Availability of appropriate surgical, anesthesia, intensive care, and blood banking capabilities
  • Availability of an obstetrical surgeon or gynecological oncologist, and general surgery, urology and interventional radiology consultants
  • Timing for peak availability of all resources and team members (if possible)
  • Availability of fluoroscopy in the operating room in case IR is required

Ideally, the decision re: Caesarean hysterectomy has been discussed and decided upon prior to entering the OR for patients at high risk of PAS.

Timing and Mode of Delivery

  • For otherwise healthy women with no history of vaginal bleeding, the optimal timing of elective Caesarean section delivery is around 34–36 weeks gestation.
  • Surgery should be considered earlier for repeated episodes of antepartum hemorrhage or contractions to reduce the risks of emergent unplanned surgery and should ideally be preceded by a course of corticosteroids to enhance fetal lung maturation if prior to 35+0 weeks gestation.

Clinical Pearl

Average time for delivery may be earlier, 33-34wGA due to bleeding, as was noted by a review of cases at a tertiary care centre in BC.

Surgical Considerations: Intraoperative Recognition

Diagnosis can be made at the time of laparotomy if the following are seen: ○Placental tissue invading lower segment, serosa, bladder ○Increased, tortuous vascularity along serosa of lower segment ○Blue/purple, markedly distended lower segment bulging toward pelvic sidewalls

If light traction on the umbilical cord after delivery of the infant pulls the uterine wall inwards with no separation, a plane should be inspected digitally between the placenta and uterus – no plane is diagnostic of PAS

If not recognized until opening on laparotomy:

  • If patient is stable and not bleeding, and the fetus not delivered yet, the abdominal incision can be closed and the patient transferred to a tertiary care facility
  • Alternatively the abdomen can be packed before the hysterotomy is undertaken, if both patient and fetus are stable, and further personnel may be recruited to the OR
  • If there is hemorrhage or the fetus is compromised, hysterotomy should be undertaken away from the placenta (fundal or posteriorly) with the placenta left undisturbed

Clinical Pearl

If at the time of laparotomy one diagnoses placenta accreta, close the abdomen and transfer the patient out as the hysterectomy in this case can be very bloody and morbid. Generally the lower uterine segment will be hypervascular – sometimes it is called a Medusa’s head. The placenta can sometimes be seen  covered by a saran wrap thin layer of serosa.

Surgical Considerations: Preparation

Regional anaesthesia may be safer than general anaesthesia as it is associated with reduced blood loss and is preferred by patients and their partners (per SOGC Guideline 383). A massive transfusion protocol should be in place to respond to significant blood loss.

Intravenous tranexamic acid should be administered at the commencement of surgery because it reduces intraoperative blood loss.

Other considerations:

  • Ureteral catheterization:  an aid in dissection or identification/repair of injury
  • Balloon-tipped intra-arterial catheter: Inserted into the internal iliac arteries pre-operatively and can be inflated following delivery of the fetus to occlude pelvic blood flow to enhance visibility and reduce blood loss. Presently there is insufficient evidence to recommend this practice routinely.

Surgery should be performed in the modified lithotomy position, using midline access, sufficiently high so as to deliver the fetus without incising through the placenta; preoperative or intraoperative ultrasound can be used to guide the optimal uterine incision.

Clinical Pearl

No attempt should be made to remove the placenta as this may cause substantial hemorrhage.

2+ large bore IVs – median EBL has been reported between 2.5-7.8L (per UpToDate).

Blood products should be made immediately available and intra-operative cell salvage considered.

ICU bed should be made available post-operatively.

There is insufficient evidence to recommend:

  • Giving or withholding uterotonic drugs after delivery of fetus.
  • Preoperative balloon placement or intraoperative ligation to arrest blood flow from internal iliac arteries prior to hysterectomy.

If bladder invasion and percreta are suspected, involvement of Urogynaecologist, Urologist, or Gynaecologic Oncologist is advised due to increased need for partial cystectomy.

Surgical Considerations: Caesarean Hysterectomy

Consider risk of requiring a hysterectomy: Confirmation of percreta or increta almost always mandates hysterectomy!

  • Make a vertical midline skin incision.
  • Inspect pelvis for signs of percreta and location of collateral blood supply.
  • Complete many dissection steps early, prior to delivery, including creating a wide bladder flap, divide the round ligament, and dissect the lateral edges of the peritoneal reflection.
  • If possible, extend these incisions to encircle the entire placental implantation site that visible occupies the prevesical space and posterior bladder wall.
  • Intraoperative U/S can be useful to map placental edge and direct hysterotomy – avoid transecting the placenta!
  • Vertical hysterotomy >2 fingerbreadths above the placental edge or a transverse fundal incision should be done to leave a myometrial margin and avoid disrupting the placenta
  • Deliver the infant and cut the cord
  • After delivery, assess the extent of placental invasion without attempts at manual placental removal
  • Close the uterine incision in 1 layer
  • Prophylactic oxytocin is not routinely administered as it can lead to partial placental separation and bleeding
  • Proceed with Caesarean hysterectomy – *would recommend transfer to tertiary center prior to this point in management

Surgical Considerations: Hemostasis

Undertake fluid resuscitation and massive transfusion, utilizing standard surgical procedures for massive hemorrhage:

  • Pressure on bleeding sites (digital, abdominopelvic packs)
  • Infrarenal aortic compression or aortic cross clamping can be done in the event of massive, life-threatening hemorrhage
  • Direct pressure on a percreta should be avoided as it may increase the size of bleeding area!

Surgical Considerations: Conservative Management

Conservative (uterus-preserving) management can be considered in:

  • Patients who insist upon preserving fertility
  • Circumstances when hysterectomy poses too great a risk of hemorrhage or to other organs, and leaving the placenta in situ may be reasonable
  • Focal accreta or a fundal or posterior placenta, thus enabling resection

Clinical Pearl

Realistically, success with this approach is variable. There is a very high rate of delayed hysterectomy.

Uterine conservation with placenta left in situ:

  • May be possible to trim the umbilical cord at placental insertion site, repair the hysterotomy in the usual fashion, and leave the placenta in-situ. Hemostatic measures (uterotonic drugs, compression sutures, balloon tamponade, uterine artery embolization or ligation) are variably used.
  • If the patient is stable, they can be transferred to a higher-level facility for definitive management.
  • This should only be attempted rarely in patients who are fully informed.
  • Delayed-interval hysterectomy can then be performed, but expert opinion advises against this approach unless circumstances are dire and there is a lack of available resources at the time of initial surgery.
  • Williams suggests that alternatively, the placenta can be left in place and can spontaneously resorb in 1-12 months although this has numerous complications including sepsis, DIC, PE, AVM.
  • Data is limited, but short-term outcomes appear suboptimal, with many patients requiring delayed-interval hysterectomy due to hemorrhage, or  hysteroscopic resection of placental remnants. 
  • Severe morbidity including sepsis, vesicouterine fistula, and uterine necrosis have also been observed. 

Clinical Pearl

Practically, this is not observed. 

Uterine conservation with placenta resected:

  • May be appropriate in focal accreta or fundal or posterior placenta accreta ○If area of morbidly adherent placenta <50%, clearly delineated, with healthy border of myometrium
  • Oversew the bleeding site or remove small wedge of uterine tissue containing adherent placenta
  • If the placenta is fundal or posterior, bleeding is often more readily controlled medically using IR or with conservative surgery
Updated on June 28, 2021

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