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    Editorial: Slow progress in management of the morbidly adherent placenta

     

    Pathogenesis of MAP: A disorder of impaired decidua

    Cesarean delivery (CD) and placenta previa are the primary risk factors for MAP. In a prospective cohort study of more than 30,000 women undergoing CD without labor by the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network, women having ≥ 4 CDs had a 9- to 30-fold increased risk of placenta accreta and a 4- to 15-fold higher risk of hysterectomy.1 Indeed the risk of accreta increased from 0.03% in women without a placenta previa who were having their first CD to 67% among those with a previa having their fourth CD.

    Because both conditions result in placentation at sites of reduced or absent decidua, the condition can be thought of as a disorder of impaired decidualization.

    Decidualization of endometrial stromal cells occurs in response to rising luteal phase progesterone and persists throughout gestation. The decidua normally poses a barrier to excessive trophoblast invasion by limiting access to tropho-trophic hormones such as insulin growth factors and vascular endothelial growth factor, impeding trophoblast-associated proteolysis, and imposing a tenacious basement-like extracellular matrix.2,3

    Equally important, the decidua creates a hemostatic milieu to prevent hemorrhage during placentation and following delivery by elaborating high levels of the primary initiator of clotting, tissue factor, and the primary inhibitor of fibrinolysis, type-1 plasminogen-activator inhibitor (PAI-1).3,4 Thus, the absence of decidua accounts for both the extraordinary trophoblastic invasiveness seen in MAP and the massive hemorrhage accompanying such deliveries.

    Prophylactic internal iliac artery balloon catheter placement for MAP

    As noted, one approach to prevention of potentially massive MAP-associated hemorrhage has been the use of prophylactic internal iliac artery balloon catheterization. The theory behind this intervention is that inflation of the balloon dramatically reduces uterine blood flow, allowing for less intraoperative blood loss, clearer operative fields, and easier, more expeditious surgery.

    Tan and colleagues reported on 11 MAP patients who underwent CD after bilateral internal iliac artery occlusive balloon placement, comparing them to 14 MAP patients undergoing CD without such placement.5 They found that balloon catheters resulted in 40% less blood loss (2011 mL vs 3316 mL; P < 0.04), 52% less blood transfused (1058 mL vs 2211 mL; P = 0.005) and a shorter duration of surgery (P < 0.05). In contrast, neither Levin and colleagues nor Shrivastava and associates demonstrated reductions in blood loss, units transfused, or hospital stays with the use of prophylactic occlusive balloon catheters in such patients.6,7

    Salim and colleagues recently reported on the first randomized clinical trial of preoperative prophylactic balloon catheters for women undergoing CD in the setting of MAP.8 In the intervention group, catheters were placed in the anterior division of the internal iliac arteries, while the control group received no catheters. The primary outcome was number of packed red blood cell (pRBC) units transfused. Patients were delivered at 34 to 35 weeks following administration of corticosteroids. Either cesarean hysterectomy (C-hys) or conservative management was offered, depending on intraoperative findings. Between 2009 and 2015, 13 women were randomized to the intervention group and 14 to the control group.

    Among the former patients, MAP was confirmed in 12 patients and 6 (50%) underwent C-hys, while 12 control patients had a confirmed MAP and 7 (58%) underwent C-hys. Among intervention patients with confirmed MAP, an average of 5.6 pRBC units were transfused and 5259 mL of blood was lost. In contrast, control patients with confirmed MAP received 4.8 units of pRBCs and had 5296 mL of blood loss. Neither these findings nor any other perioperative outcome was statistically different between the 2 groups.

    While the numbers of patients studied were small and the degree of MAP-associated pathology modest, as suggested by the relatively large number of patients conservatively managed, these findings certainly do not indicate an overwhelming and universal utility to preoperative prophylactic iliac artery balloon catheter placement.

    Charles J. Lockwood, MD, MHCM
    Dr. Lockwood, Editor-in-Chief, is Dean of the Morsani College of Medicine and Senior Vice President of USF Health, University of South ...

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