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9/1/2017

Management of Placenta Accreta at Delivery

 

Placenta accreta spectrum (PAS) describes the pathologic adherence of the placentaand includes placenta increta, percreta, and accreta. The PAS incidence has increased in parallel with increasing cesarean delivery rates, going from .02% in the 1970’s, to 1 in 272 patients with a birth-related discharge diagnosis in 2016.  The greatest risk occurs in women with placenta previa overlying the uterine scar. Accreta risk with placenta previa is 3% with one prior cesarean delivery, increasing to 67% with five.   Historically, delivery blood loss is on average up to 5 liters, and mortality rates have been reported to be as high as 7%.  Given these risks, diagnostic evaluation, pre-delivery planning with multidisciplinary teams, and delivery at an ACOG/SMFM maternal level of care 3 or 4 facility with massive transfusion capacity is essential.  The care team should include obstetricians, anesthesiologists, and neonatal specialists, with gynecology-oncology, surgery, urology, critical care, interventional radiology, and transfusion specialists available if necessary.

Pre-delivery diagnosis is typically made by recognizing risk factors and by ultrasonography, with magnetic resonance imaging reserved for ambiguous, high-risk, or high-suspicion cases.  The most predictive ultrasound finding is placenta previa, which is present in more than 80% of placenta accretas.Multiple vascular lacunae in the placenta, thinning of the myometrium overlying the placenta, loss of retroplacental clear space, decreased retroplacental myometrial thickness (<1mm), and increased vascularity of the uterine serosa-bladder interface are also suggestive.  

When identified antenatally, recommended surgical management is a planned, preterm cesarean-hysterectomy at 34-35 weeks 6 days, with placenta left in-situ. This approach can be individualized for women with strong future fertility desires.  All patients should be counselled regarding risks including massive blood loss and transfusion, urologic injury, and death.  Planned delivery is preferred due to lower blood loss and complications than with emergent cesarean-hysterectomy. Preoperative planning should include checklists for scheduled and emergent scenarios, as well as administration of late preterm steroids for fetal lung maturation.

The role of preoperative balloon catheterization of the internal iliac or uterine arteries is controversial. Due to the risks of serious complications including arterial damage, infection, and occlusion, routine balloon catheter placement is not recommended. It is unclear if preoperative ureteral stenting is beneficial.  A three-way Foley catheter may help with bladder distention and surgical dissection.  Regional or general anesthesia can be used as clinically appropriate.   Supplemental prophylactic antibiotic doses are often necessary given hemorrhage and prolonged operative time. Patient positioning in modified dorsal lithotomy with stirrups allows for vaginal bleeding quantification, placement of vaginal packing, and room for an additional surgical assistant.

A vertical midline skin incision should be considered for exposure.  Based on preoperative ultrasound assessment, the hysterotomy should be made away from the placental location, which may require classical or fundal entry.  With elective cesarean-hysterectomy, the placenta should be left in-situ and the hysterotomy should be quickly stitched closed to facilitate hemostasis before hysterectomy.  In patients desiring fertility, manual placental removal may be cautiously attempted after adequate counseling about its association with significant complications including large blood loss and high likelihood of failure requiring hysterectomy.  Not all accreta cases are identified antenatally. Some are recognized when the placenta does not separate after fetal delivery. The multidisciplinary team and blood bank should be immediately alerted. Prompt replacement of blood products in the ratio of 1:1:1 to 1:2:4 of packed red blood cells: fresh frozen plasma: platelets is recommended.  Intrauterine balloon tamponade and tranexamic acid may help minimize blood loss while necessary preparations are made. 

Hysterectomy is generally performed in the usual fashion.  Supracervical hysterectomy can decrease the chance of bladder or ureteral injury, however total hysterectomy may be required if there is persistent cervical bleeding.  Cases of percreta often need more extensive surgical management. Conservative or expectant management of placenta previa should be rare and considered only in individual cases.

Further Reading:

American College of Obstetricians and Gynecologists; Obstetric Care Consensus No. 7: Placenta Accreta Spectrum. Obstet Gynecol. 2018 Dec;132(6):e259-e275. doi: 10.1097/AOG.0000000000002983.

Initial approval July 2017, Revised January 2019, Reaffirmed September 2020, Minor Revision March 2022, Reaffirmed January 2024.

 

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