Better results have been reported by some using threedimensional (3-D) sonography and power Doppler (Collins, 2015; Doyle, 2015). We too have found that the addition of Doppler color low mapping is highly predictive ofmyometrial invasion (Fig. 41-28). This is suspected if the distance between the uterine serosa-bladder wall interface and the retroplacental vessels measures < 1 mm and if there are large intraplacental lacunae (Rae, 2015a; Twicler, 2000). Similarly, Cali and associates (2013) reported that hypervascularity of the uterine serosa-bladder wall interface had the highest positive-and negative-predictive values for placenta percreta.
MR imaging can be added to outline anatomy and to identiy invasion of adjacent structures, including possible ureteral involvement (Chalubinski, 2013; Reddy, 2014). Although gadolinium is usually not added during pregnancy, this contrast may enhance images (Millischer, 2017). Lax and coworkers (2007) described three MR imaging findings that suggest accreta: uterine bulging, heterogeneous signal intensity within the placenta indicative of lacunae, and dark intraplacental bands on T2-weighted imaging. Some recommend use of MR imaging if sonography results are inconclusive or there is a posterior previa (American College of Obstetricians and Gynecologists, 2017c; Silver, 2015a).
FIGURE 41-28 Transvaginal sonogram of placental invasion with a morbidly adherent placenta. Retroplacental vessels (white arrows) invade the myometrium and obscure the bladder-serosal interface. Abnormal intraplacental venous lakes (black arrowheads) are commonly seen in this setting.
Preoperative assessment ideally begins once a possible accrete syndrome is recognized antenatally (Fitzpatrick, 2014; Sentilhes, 2013). A major decision concerns the timing of and the ideal aciliy or delivey. Considerations include appropriate surgical, anesthesia, intensive care, and blood banking capabilities. n obstetrical surgeon or gynecological oncologist and surgical, urological, and interventional radiological consultants should be available (Brennan, 2015; Shamshirsaz, 2015). he American College of Obstetricians and Gynecologists (2017c) and the Society for Maternal-Fetal Medicine (2010) recommend planned delivery in a tertiary-care facility. In some of these, specially designed teams have been assembled and are on call (AI-Khan, 2014; Erfani, 2017a; Smulian, 2017; Walker, 2013).
Silver and colleagues (2015b) have provided criteria for accreta centers of excellence. Shown in Table 41-5 are some
TABLE 41-5. Criteria for Consideration of Delivery in an Accrete Center of Excellence
Placenta previa with abnormal ultrasound appearance
Placenta previa with ::3 prior cesarean deliveries
Inability to adequately evaluate or exclude placenta accreta
Any other reason to suspect morbidly adherent placenta
Reproduced with permission from Silver, 201Sb.
criteria to consider transfer to a higher level-of-care facility. Women who refuse blood or its derivatives pose especially diicult management dilemmas (Barth, 201r1). If possible, delivery is best scheduled for peak availability of all resources and team members. Even so, a third of cases require unscheduled delivery, and contingency plans should be ready (Pettit, 2017) .