Placenta accreta is a potentially life threatening condition that continues to challenge the medical field. The prevalence has been on a steady rise over the last few decades, currently between 1 in 533 to 1 in 731 of all deliveries,¹ becoming a commonality in obstetrics. Placenta accreta is defined by an abnormal attachment between the placenta and the myometrium of the uterus. The extent of invasiveness is categorized into three different categories: accreta, increta, and percreta. Chorionic villous attachment beyond the normal boundary of Nitabuch layer with superficial attachment of the myometrium is an accreta, villous invasion into the myometrium is increta, and villous invasion up to and beyond the uterine serosa is a percreta. Most morbidities present during the delivery stage and include complications such as uterine atony or postpartum hemorrhage, which can lead to disseminated intravascular coagulopathy, renal failure, or require hysterectomy. Mortality rates increase directly with the degree of invasion and can reach a level as high as 7%.¹

A cesarean hysterectomy is an evolved operative procedure that dates back to 1896 when the first human cesarean hysterectomy was performed in the United States. Soon after, Porro of Milan performed the first cesarean hysterectomy in which both mother and fetus survived: coining the alternate name of the “Porro Procedure.”² Historically, this particular procedure was used as a last resort during life-threatening hemorrhage. With advances in medicine, surgical procedures, and diagnostics, cesarean hysterectomies can now be utilized for a variety of indications. Cesarean hysterectomy is the most common treatment for abnormally invasive placentation. Not surprisingly, the rates of cesarean hysterectomies are increasing. The operation can often times be straightforward to any gynecologic surgeon, if it is carefully planned and meditated upon; the risk of morbidity increases during emergent and time sensitive situations. Morbidities of cesarean hysterectomy include, but are not limited to, hemorrhage, vascular injury, damage to the urinary tract system, and even death.

The intricacies of a cesarean hysterectomy often extend beyond the scope of a general gynecology. Recent research has started to show improved outcomes for patients with abnormally invasive placentation using a multidisciplinary approach and in specialized centers. Commonly observed outcomes with a cesarean hysterectomy include increased blood loss, intraoperative injury, and intensive care unit (ICU) admission. The contributions of specialties such as interventional radiology, trauma, urology, anesthesia, and blood bank services are priceless and can complement the surgical skills of experienced obstetrical or gynecologic surgeons. Every placenta accreta presents a unique challenge; therefore a well-studied and organized team will offer the greatest chance for a successful outcome.

The mechanisms leading to development of a placenta accreta are not well understood and are likely multifactorial. Endometrial damage is a common preceding risk factor, resulting in scar tissue that interferes with normal placentation: previous cesarean, dilation and curettage, endometrial ablation, and myomectomy entering the uterine cavity. Placenta previa is an important independent risk factor (Table 29-1). The estimated risk of an accreta at the primary cesarean without a placenta previa is 0.03% and remains less than 1% at the fifth cesarean section. The presence of both a placenta previa and one previous cesarean section has an accreta risk of 11%. This number increases to 67% when a previa exists in the setting of four previous cesarean sections. An anterior previa has the highest risk for accreta followed by a central previa. Historically, factors such as multiparity, age, substance abuse, and reproductive technology have been associated with placenta accreta but the exact reasons for these risk factors and their contributions are still under investigation.

The initial evaluation for placenta accreta is usually by ultrasonography. The evaluation often begins during the second trimester, and some studies have evaluated early first trimester findings. Evidence of low implantation or cesarean scar ectopic is predictive of abnormally invasive placentation. Other diagnostic signs start to present around the 15th week of gestation, although when used prior to 15 weeks have a lower sensitivity. The earliest and most predictive findings are lacunae, or vascular lakes, with a sensitivity of 79% and positive predictive value of 93%.³ Sensitivity increases significantly to 93% after 20 weeks gestational age. The number of lakes is directly proportional to the risk of an accreta. Loss of the hypoechoic zone is a well-known and commonly used marker for diagnosing an accreta, and has a sensitivity of 57% at less than 20 weeks gestational age, and only 80% at 20 weeks.

Color Doppler can be used with ultrasound to assess vascular flow in the placenta. As an independent modality, color Doppler does not add great diagnostic benefit but it can be helpful when looking at the serosa-bladder wall. Increased vascularization along both the uterine serosa-bladder wall and perpendicular to the uterine wall has the highest positive predictive value of 92%.

A list of the common ultrasonographic findings can be seen in Table 29-2. Each ultrasound finding carries its own advantage in diagnostics, and the presence of more than one marker increases the overall predictive value.

Magnetic resonance number (MRI) has gained popularity in diagnostics for placenta accreta. The use of MRI does not have any greater sensitivity than ultrasonography alone for diagnosis of placenta accreta (Table 29-3).⁴ MRI can offer advantages that ultrasonography cannot. For example, MRI has a positive predictive value (PPV) of 85% when it detects focal bulging and can be as high as 90% when dark intraplacental bands are seen with T2 weighted images. MRI can also be useful when evaluating a posterior placenta that generally has limited views from ultrasonography, evaluating extension into surrounding organs, or preoperative planning.

In addition to imaging, there is a relationship between maternal serum markers and abnormal placentation. The earliest marker available for screening is pregnancy-associated plasma protein A (PAPP-A). Desai et al. found a significant relationship demonstrating a PAPP-A of more than 2 MoM doubled the risk for an accreta and a PAPP-A of more than 3 MoM increased the risk 4-fold.⁵ The study demonstrating this relationship was limited by sample size but lays a groundwork for future research. Maternal serum alpha-fetoprotein (MS-AFP) is another significant marker to consider monitoring. Similar to PAPP-A, studies are limited, but Hung et al. demonstrated that an MS-AFP level more than 2.5 MoM, in conjunction with a placenta previa and a previous cesarean, was associated with an increased risk for invasive placentation.⁶

A careful approach to management must be pursued when there is a suspicion of an abnormally invasive placentation. Early diagnosis, planning, and preparation are keys to successful surgery and reducing blood loss at time of delivery. Antenatal diagnosis of invasive placentation occurs in approximately 50% to 53% of patients. Whenever feasible, the management and delivery of a patient with a suspected abnormally invasive placenta would take place in an appropriate Maternal Level II, III, and IV facility. Centers with appropriate experience, such as a Center of Excellence, often times use a multidisciplinary team approach, track outcomes, and perform continuous quality improvement to optimize results. When not performed in such centers, an experienced team is recommended. Early referral to centers specializing in the management of patients with an abnormally invasive placenta should take place as soon as suspected so that patients may have early access to consultants, diagnostic imaging, and counseling regarding treatment options.

The risk of maternal and fetal mortality may be as high as 7% and 9% for maternal and fetal mortality, respectively. Early referral may allow patients to determine their options for termination of pregnancy, delivery timing, delivery methods, and future child bearing needs. At this time definitive surgical management is recommended, although uterine preserving or conservative management may be used in select patients.

Timing of delivery is recommended prior to the onset of labor. The risk of spontaneous bleeding or labor increases after 30 weeks gestation, and patients should be counseled on those risks. Ideal timing for delivery is recommended at 34 weeks⁷ based on a decision tree analysis comparing delivery strategies from 34 to 39 weeks in patients with an accreta and a previa, with or without amniocentesis. The findings suggest better outcomes with an early delivery preferably at 34 weeks, and showed no utility in determining lung maturity via amniocentesis. Patients without a previa may reasonably be delivered at 37 weeks gestational age. There may be limited situations in which a delivery may be considered after 37 weeks, such as patients where the diagnosis is in doubt and no prior uterine surgeries or previa. Delivery prior to labor or active bleeding may have shorter operative times, blood loss, and length of stay. The ultimate decision should take into consideration the individual patient and their desires, confounding risk factors, fetal well being, provider comfort, and availability of hospital resources.

Delivery options are an important discussion that must include the patient, delivery provider, and other disciplines. A cesarean hysterectomy is the definitive treatment for abnormally invasive placentation, and may be the most effective method. Alternatives to a planned cesarean hysterectomy, such as conservative management or a delayed hysterectomy, are considered experimental and should not be the default method of management. If these options are pursued, it is recommended to be with a center that has experience or expertise for managing and monitoring the complications associated with alternative treatment. Candidates for conservative management and delayed hysterectomy must be carefully chosen and may include those with a fundal placenta, a small localized accreta, or a posterior accreta. Patients must be counseled extensively on the risks, and will require a prolonged period of observation until resolution.

Prior to beginning any surgical intervention, the level of anesthesia needs to be discussed. There are no known advantages for general anesthesia, regional anesthesia, or a combination of both with abnormally invasive placentation. The use of a combined spinal/epidural is not unreasonable based on delivery planning and expectations. Regional anesthesia presents fewer complications overall than general anesthesia. The patient should always be consented for both types of anesthesia and informed that transition from regional to general during the procedure is a possibility. Preoperative anesthesia consultation may also include the decision for two large bore IVs, an arterial line, and when a central line would be placed. Prior to beginning the procedure, the patient should have a current (within 72 hours) type and screen and baseline hemoglobin and hematocrit in anticipation for the need for blood products. A Foley catheter should be in the bladder, sequential compression devices in place, and consider a rectal tube (ie, Zassi™) in the vagina in order to collect and monitor vaginal bleeding.

Surgical Approach

A staged surgical approach is often used with multidisciplinary approaches. The first step may include evaluating the urinary tract and placing ureteral stents. This may aide the intraoperative evaluation of the ureters, although a distinct advantage has not been demonstrated in studies. The most common type of stent is the JJ stent, which is a flexible plastic tube varying in length between 24 and 30 cm. A vertical midline incision offers better visualization and access in preparation for complications and may be the preferred entry to facilitate uterine entry or control of vascular pedicles. External inspection of the uterus is valuable to confirm findings consistent with abnormally invasive placentation, and may be the surgeon’s first signs if it is undiagnosed (Figs. 29-1A and B). Intraoperative ultrasound for placental mapping can confirm preoperative findings suspicious for invasive placentation, and to identify the limits of the placenta.

It is advisable to make a uterine incision that will not disturb the placenta. In the case of an anterior or even fundal placenta, exteriorizing the uterus may be required (Figs. 29-2A and B). The uterine serosa may be marked (suture or electrocautery) with a 1 to 2 cm margin of clearance from the perimeter of the placental edge (see Fig. 29-2A). In some cases, a transfundal or posterior uterine incision may be required (Figs. 29-3A and B). Some centers also employ use of a uterine stapler to make the incision which may decrease blood loss. The fetus is delivered without manipulation of the placenta to avoid partial placental separation. The edges of the uterine incision may be clamped (Fig. 29-4A), or sutured with a locking or running suture to decrease bleeding. The hysterotomy may be left open, but is often closed with a locking or running suture (Figs. 29-4B to D).