**2. Imaging findings**

Imaging in the antepartum should be performed with minimal risk to both the mother and developing fetus. Noninvasive techniques such as ultrasound (US) and magnetic resonance imaging (MRI) that do not use ionizing radiation are thus the preferred imaging techniques. The advantages of MRI are superior soft-tissue contrast resolution, multiplanar imaging capabilities, wider field of view, and image quality independent of the mother's size or fetus positioning. Thus, it may be superior to US in some settings [1, 2].

However, US remains the primary method of imaging the placenta. Also, its high negative predictive value for placental abnormalities assigns MRI to a supporting role reserved for equivocal US findings or incomplete evaluation as in cases of posterior placenta [5].

### **2.1. Ultrasound**

Ultrasonography is the primary screening tool for placental invasion in women at high risk of AIP usually performed during the second and third trimesters of pregnancy [8–10]. Its sensitivity for the diagnosis of AIP ranges from 77 to 93% and specificity from 71 to 97% according to a recent review [6, 8, 11], but its sensitivity and specificity may increase to 100% when applied to a high-risk population [3].

Many US signs are described for the diagnosis of abnormal placental invasion. These signs include the following [3, 8, 9]:


In addition, we should emphasize on the US limitations especially regarding the difficult access to posterior placental locations, the evaluation of the degree of placental infiltration, or the presence of associated myometrial lesions [4, 10, 12, 13].

### **2.2. Magnetic resonance imaging (MRI)**

placenta percreta is the most severe with invasion of uterine serosa or adjacent pelvic organs [1, 2]. It is worth noting that when the myometrium becomes very thin especially at the level

The frequency of abnormal invasive placentation (AIP) has risen in the last 30 years parallel to the increase in cesarean delivery rate [3, 4]. Other common risk factors for abnormal placentation include placenta previa, prior myomectomy or other uterine surgery, and advanced

AIP is a life-threatening condition due to massive hemorrhage and urgent need for blood transfusion, the need for peripartum hysterectomy, damage to adjacent organs due to placental invasion, and the need for admission to the intensive-care unit [4, 6, 7]. For these reasons and their consequence of decreasing the burden of maternal morbidity-mortality, it is essential to accurately diagnose the degree of placental invasion. The major predicting determinant

Imaging in the antepartum should be performed with minimal risk to both the mother and developing fetus. Noninvasive techniques such as ultrasound (US) and magnetic resonance imaging (MRI) that do not use ionizing radiation are thus the preferred imaging techniques. The advantages of MRI are superior soft-tissue contrast resolution, multiplanar imaging capabilities, wider field of view, and image quality independent of the mother's size or fetus

However, US remains the primary method of imaging the placenta. Also, its high negative predictive value for placental abnormalities assigns MRI to a supporting role reserved for

Ultrasonography is the primary screening tool for placental invasion in women at high risk of AIP usually performed during the second and third trimesters of pregnancy [8–10]. Its sensitivity for the diagnosis of AIP ranges from 77 to 93% and specificity from 71 to 97% according to a recent review [6, 8, 11], but its sensitivity and specificity may increase to 100%

Many US signs are described for the diagnosis of abnormal placental invasion. These signs

**1.** Loss or irregularity of the hypoechoic plane in myometrium underneath placental bed

**2.** Multiple placental lacunae, often containing turbulent flow visible on grayscale or color

equivocal US findings or incomplete evaluation as in cases of posterior placenta [5].

of the cesarean section, difference between accreta and increta is obsolete.

of the outcome of women affected of AIP is the depth of placental invasion [3].

positioning. Thus, it may be superior to US in some settings [1, 2].

("the clear zone") or retroplacental myometrial thinning <1 mm

maternal age [5].

74 Placenta

**2. Imaging findings**

**2.1. Ultrasound**

when applied to a high-risk population [3].

include the following [3, 8, 9]:

Doppler US

MRI is a secondary diagnostic tool for AIP and indicated when US is limited and inconclusive or in cases of a posterior placenta [4, 6, 7, 10, 14]. The examination typically is made between 24 and 32 weeks of gestational age, in a supine position, but if not tolerated it can be made in left lateral decubitus or oblique position. The bladder is partially distended during the study. MRI protocol is essentially based on three-plane T2 sequences for the placental assessment (single-shot T2-weighted fast spin echo sequences or T2-weighted TSE); a T1-weighted sequence can be acquired, and recently, the utility of diffusion-weighted imaging is discussed in many studies [6]. Although contrast-enhanced imaging can improve the diagnostic accuracy of placental invasion while improving the contrast between the myometrium and the placenta, gadolinium usage during pregnancy should be avoided [6, 7]. MRI signs suggesting AIP include the following [4, 6, 10, 15]:


management of morbid placental adherence to minimize potential maternal or neonatal morbidity and mortality [17]. Coordination with the blood bank before beginning the procedure is essential to ensure adequate supplies of red cells, platelets, and fresh frozen plasma [16]. In their study, Brennan et al. have also specified that the early presence of a gynecologic oncologist at delivery is a key predictor of reduced blood loss and transfusion requirements when abnormally invasive placenta is suspected [18]. Furthermore, other authors have reported that outcomes are improved if delivery takes place in centers with multidisciplinary expertise

Placental Malformation: Accreta and Beyond http://dx.doi.org/10.5772/intechopen.80588 77

Cesarean hysterectomy in cases of placenta percreta is often technically challenging due to the anatomic and physiologic changes of pregnancy, including a massive increase in blood flow to the uterus at term. The vessels that supply the uterus, ovaries, and bladder are substantially larger and more tortuous in pregnancy than they are in the nonpregnant state. Meticulous care in the manipulation of clamps, cutting of pedicles, and placement of sutures is required to prevent severe bleeding. Scarring from previous surgery, particularly previous cesarean sections, is a common complicating feature of cesarean hysterectomy [20]. These cesarean hysterectomies often require difficult dissection of poorly defined tissue planes, particularly of the bladder interface, and partial bladder resection is often required [21]. All these factors make this procedure associated with a higher risk of complications in comparison with

In the literature, few reports of a well-standardized technique describe the steps of a cesarean hysterectomy among women with placenta percreta who need radical treatment. When performing such a procedure, the major concern is to prevent ureteral lesions in a pelvis with a distorted anatomy and to reduce blood loss. A recent study has demonstrated the effectiveness and safety of a well-standardized approach for managing all cases of placenta percreta

It is preferable to schedule cesarean hysterectomy in case of placenta percreta starting at 34 weeks of gestational age. However, cesarean is sometimes carried out as an emergency procedure irre-

The technique that we intend to describe was developed based on collected experience in gynecologic oncology. First of all, the placement of ureteral stents is not necessary according to this technique since it is not always possible especially during emergencies in cases with massive bleeding [24]. The surgeon starts with a vertical midline incision under general anesthesia. A peroperative US is performed to localize the placenta and to guide the surgeon while performing the hysterotomy. After delivery of the baby, the surgeon proceeds with a closure of the uterine incision with Vicryl® "0" hepatic needle sutures (Ethicon, Johnson and Johnson Companies, Somerville, NJ, USA). In a next step, the surgeon approaches the retroperitoneum just lateral to the adnexal ligaments to secure the ureters and to clip the uterine arteries at their origin after opening the paravesical space. The uteroadnexal ligaments also need to be ligated as close as possible to the uterus. After clipping the uterine arteries, these are lifted up

abdominal hysterectomies performed for benign indications [22].

spective of gestational age in cases of heavy bleeding or fetal distress.

and experience in PAS disorders [19].

**3.1. Surgical technique**

and in all circumstances [23].

**Figure 1.** A 26-week-old fetus with placenta praevia showing: **A**. An increased vascularity seen in the lower uterine segment and the interface with the bladder seen on a sagittal image on US. **B**. On 1.5 MRI, sagittal sequence T2WI: a heterogeneity in the placenta (arrow) overlying the internal os (double arrows) with involvement of surrounding structures and focal myometrial interruption with extension into the bladder wall (**C**, arrowhead). **D**. On axial sequence T2WI: a heterogeneity in the placenta with dark intraplacental bands (double arrowheads). This was consistent with percreta on surgery and histopathology.
