August 2016 Case 1

A 20 year-old female for concurrent C-section and supracervical hysterectomy

Rachel Whitehair, MS3, Janice Ahn, M.D., H. James Williams, M.D.


The patient is a 20-year-old G2P0101, former smoker, whose first pregnancy was complicated by pre-term birth of an infant with gastroschisis. She had received prenatal care and was otherwise healthy. Delivery was by low transverse Cesarean section.

During the second pregnancy, for which she also received prenatal care, second trimester ultrasound revealed an anteriorly-placed placenta with an irregular thickening along its margins. There was a loss of the normal myometrium in the anterior segment of the uterus and absence of the serosal margin between the myometrium and the bladder. Additionally, there appeared to be extensions of vascular structures into the bladder that had active blood flow via Doppler ultrasound.  The cervix was intact.

Due to the ultrasound findings of a placental anomaly, including increased vascularity, a decision was made to proceed directly from the fetal delivery to hysterectomy. Accordingly, the patient underwent an uncomplicated cesarean delivery with supracervical hysterectomy at 36 weeks.  The patient remained hemodynamically stable post-operatively.

Gross and Microscopic Descriptions


The uterus was removed with the placenta still intact (see images 1 and 2). Together they weighed 1062 grams and measured 20.7 x 14.1 x 8.1 cm. The placenta was adherent to the anterior uterine wall. The placenta measured 17.8 x 13.0 x 3.4 cm and extended into the internal os and through the myometrium. An 8.5 x 3.5 cm defect in the uterine wall was noted, and the maternal surface of the placenta was visible through a defect. The placenta had a purple-gray fetal surface with minimal sub-chorionic fibrin deposition. Serial sectioning revealed red-brown placental parenchyma extending into the myometrium. The membranes and three-vessel umbilical cord were grossly unremarkable.

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Image 1. Bivalved uterine fundus with placenta adherent to the anterior wall.
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Image 2. Cross section of placenta and uterine wall.


Microscopic examination revealed no abnormalities in the fetal membranes or umbilical cord. The sections through placental parenchyma revealed chorionic villi appropriate for gestational age. Sections through the uterine wall revealed full thickness invasion of placental tissue into the anterior myometrium (see images 3 – 5).

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Image 3. Chorionic villi appropriate for gestational age.
Image 4. Full thickness invasion of placental tissue, including chorionic villi and fibrin, through anterior myometrium to serosa (arrow).
Image 5. Additional section of full thickness invasion of placental tissue through anterior myometrium to serosa (arrow).


Differential Diagnosis?


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Background and risk factors

Placenta percreta is a form of adherent placenta that invades through the uterine myometrium to the serosa. In some cases the villi invade through the serosa into the surrounding tissues.  It is one of the three types of adherent placentas that includes acreta in which placenta adheres to the superficial myometrium, and increta where the placenta invades into but not through the myometrium.  The incidence of adherent placentas is sizeable. They complicated 1 out of 3,000 deliveries in 2000, increasing from 1 in 30,000 in the 1930’s.1 Percreta is the rarest of the three forms and occurs in 5-7% of adherent placenta cases.2

The pathophysiology behind adherent placentas is not well known, but is believed to be a result of an abnormality or absence of the decidua basalis, the precursor of the maternal component of the placenta. This defect is thought to permit invasion into the underlying myometrium.2

The greatest risk factor of adherent placenta is a previous Caesarian section (CS) with the risk increasing for each following CS.3 The uterine incision of a CS and other scaring procedures allow for the formation a fibrous scar with little to no smooth muscle cell proliferation and decreased to absent endometrial layer reformation.  When the placenta implants over a scar site, there is minimal decidua basalis formation due to the lack of a normal endometrial layer; this abnormality is thought to lead to an invasive placenta. Other reported risk factors for placenta percreta have included high parity, advanced maternal age, leiomyoma, Asherman’s syndrome, myomectomy, prior dilation and curettage, prior manual placental extraction, and in one case, radiation exposure.4  Each of these leads to an abnormality in the formation of or frank absence of the decidua basalis.  Interestingly, the presence of adenomyosis (endometrial tissue present within the myometrium) does not increase the likelihood of adherent placentas.5 In the absence of a CS, there is a 4% risk of an adherent placenta with placenta previa, where the placenta implants near or over the cervical os. Placenta previa and a CS have a combined risk of adherent placenta ranging from 3% in the first post-Caesarian pregnancy to 60% by the fourth pregnancy.3

Radiologic findings

Adherent placentas are typically recognized by ultrasound in the second trimester. The accuracy of ultrasound diagnosis is still under investigation, but it is the most common imaging modality used to identify abnormalities in placentation. The ultrasound findings for an adherent placenta pertain to the appearance of the tissue planes and surfaces between the placenta, uterus, serosa, and bladder.  The interface between the uterus and placenta is typically echolucent with a visible clear space on ultrasound image without any irregularities caused by invading trophoblastic tissue. Loss of space between the uterus and placenta is not diagnostic, but an adherent placenta cannot be entirely ruled out.6

Additionally, hypervascularity, identified by Doppler ultrasonography, between the uterine serosa and bladder interface increases the probability of an adherent placenta. The presence of vascular channels protruding into the bladder is more suggestive of a percreta than an acreta or increta.6 Finally, imaging modalities such as magnetic resonance imaging (MRI) may be used as a supplement for radiologic diagnosis but ultrasound remains the imaging technique of choice.7,8

Pathologic findings

As described above, the placenta will appear grossly normal except for its adherence to the uterine wall.  Commonly this occurs on the anterior wall in patients after a CS.6 Histologically, the placental tissue appears normal except that it extends through the myometrium. The villi are composed of the outer syncytiotrophoblast and cytotrophoblastic layer enclosing loosely spindled villous stroma. The vessels within the chorionic villi correspond to the hypervascularity seen by Doppler ultrasound. In the presence of a defect in the decidua basalis, the trophoblastic tissue continues to grow deeper through the myometrium, and in the case of percreta, can be seen adjacent to or invading through the uterine serosa.

Clinical considerations

Placenta percreta often presents with occult clinical symptoms. As the symptoms correlate with the depth of invasion of surrounding tissue, percretas that do not reach beyond the serosa may be asymptomatic and thus difficult to diagnose. On the other hand, involvement of the bladder may cause painless hematuria. In severe cases, where there is bowel or peritoneal involvement, patients often present with acute abdomen.9

Percreta placentas have a perinatal mortality rate of 24% and maternal morbidity of 9.5%10 and thus require careful management to ensure safe delivery for both mother and infant. Delivery is usually via scheduled CS at 34-36 weeks with consideration of additional management for percreta involving additional pelvic structures. On the other hand, those that do not invade beyond the serosa may be managed conservatively or via hysterectomy.

Total abdominal hysterectomy or subtotal/supracervical hysterectomy (if the cervix is uninvolved) at the time of CS provides definitive management for placenta percreta. After the infant is delivered and blood loss minimized, the uterus together with the attached placenta is removed. This approach is typically limited to cases where the placenta is confined to the serosa.11  Unfortunately, with this method there is no preservation of fertility.

Conservative management consists of allowing the body resorbs placental tissue and minimizing risk of injury to surrounding structures. However, conservative treatment does not eliminate the risk of hemorrhage or serious infection. Shabana et al12 estimated that of those undergoing conservative treatment, 58% will require a hysterectomy in the following 9 months. One study found the risk of at least one complication for conservative management was 61% compared to 12% for operative management.13 Another study showed that even with resolution of the current percreta via conservative management, 60% of patient had recurrence of another type of adherent placenta during their next pregnancy. 

Complications of a percreta delivery include bowel injury, bladder injury, peripartum hysterectomy, coagulopathy, amniotic fluid embolism, hemorrhage and death.10 Obiren11 found that 28% were associated with postpartum infection and 90% of percreta cases required a blood transfusion.  Severe hemorrhage is an ominous complication and even scheduled CSs can prove dangerous due to blood loss, which corresponds to the depth of placental invasion into the myometrium. If a percreta is overlooked prior to labor, the risk of hemorrhage and maternal mortality is even greater. Often interventional radiologic techniques to reduce blood loss, such as embolization or occlusive stenting, are warranted.11 


In our case, the patient’s ultrasound findings were suggestive of either a percreta or increta placenta. The presence of vascular structures with positive blood flow on Doppler ultrasound was suggestive of a percreta.  Combined with the patient’s history of a previous CS, there was a high likelihood of placenta percreta.  The patient underwent a second CS and a supracervical hysterectomy was performed. There were no surgical complications. Grossly, the placenta penetrated through the myometrium to the serosa through a defect in the posterior uterine wall and the maternal surface was visible through the uterine wall defect. Microscopically, the chorionic villi had no abnormalities but penetrated through the myometrium to the serosa and thus, placenta percreta was diagnosed.


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