Placenta Accreta Facts

Placenta accreta, an abnormally deep attachment of the placenta into the endometrium and myometrium (the middle layer of the uterine wall), complicates 3% of primary, 11% of secondary, 40% of tertiary, 61% of quaternary, and 67% of higher-order cesarean sections for placenta previa.⁶

The most common risk factor for abnormal placentation is previous cesarean section, but any invasive procedure that might affect the endometrium (including curettage, hysteroscopic surgery, myomectomy, and endometrial ablation) can increase the risk.

Differences in oxygen tension in abnormal placental beds have been invoked as a cause of abnormal placental invasion. It has been reported that preferential implantation of embryos into a relatively avascular scar tissue occurs because of decreased oxygen tension.⁹

Although the optimal timing for delivery is uncertain, early delivery is often recommended to minimize additional risks that are associated with emergent surgery.

Transcatheter arterial embolization for the control of obstetric hemorrhage has been shown to reduce blood loss and avoid hysterectomy in some cases.

Adequate blood products should be immediately available for transfusion with a rapid infuser. Evidence is now in favor of cell salvage in obstetrics, although this finding remains controversial.¹⁸ Recent evidence indicates that preoperative placement

Preoperative placement of ureteral stents is also associated with improved clinical outcome because clear identification of the ureters allows rapid completion of the hysterectomy.

 A vertical midline incision may be considered to achieve optimal visualization.

Many planned cesarean sections for placenta accreta are done with general anesthesia because of concerns for hemodynamic instability and the potential requirement for massive transfusion. However, in a classic study of cesarean hysterectomy at five institutions from the 1980s, 32% of planned cesarean hysterectomies were performed under regional anesthesia. There was no difference in intraoperative blood loss or hypotension, and no one required induction of general anesthesia.

If regional anesthesia is chosen, it is important to counsel the patient and her family about the possibility of conversion to general anesthesia in the setting of massive hemorrhage

Case series heavily populated by placenta accreta often document transfusion requirements of four to six units of pRBCs.

Anesthesiology:

October 2011 - Volume 115 - Issue 4 - p 852–857