Placenta accreta spectrum: Clinical sciences

The placenta accreta spectrum, known as PAS, refers to a range of abnormal placental invasion and adherence into the myometrial tissue of the uterus. It occurs when there is an abnormal interface between the uterine endometrium and myometrium.

This often occurs over a uterine scar, which is why placental trophoblasts anchor deeper than normal into the uterine wall. The spectrum ranges from placenta accreta, where the placenta attaches to the myometrium; then, placenta increta, where invasion into the myometrium occurs; and placenta percreta, where the placenta penetrates through the myometrium and attaches to the uterine serosa; sometimes adjacent organs are also invaded, like the bladder.

PAS can be suspected antenatally, but sometimes isn’t discovered until after delivery, where life-threatening hemorrhage is often encountered when placental separation is attempted, due to this abnormally deep attachment.

Your first step in evaluating a patient presenting with a chief concern suggesting PAS is to do a CABCDE assessment to determine if they are stable or unstable.

Unstable patients typically present right after delivery of the baby, when attempting to deliver the placenta. This should already make you suspect PAS. In this case, first, control the hemorrhage and stabilize the airway, breathing, and circulation. You may need to intubate the patient. Then, obtain IV access, and continuously monitor their vital signs.

To confirm the diagnosis of PAS, you will need to obtain a focused history, physical exam, and labs including CBC, PT, INR, PTT, and fibrinogen. Additionally, a uterine ultrasound performed at the bedside will help with diagnosis. However, don’t delay treatment while waiting for the diagnosis, since the hemorrhage can be life-threatening!

Okay, so your patient may have a history of procedures that lead to uterine scarring. The big one to look out for is a prior c-section birth. Others include myomectomy or dilation and curettage, also referred to as D&C. The risk of PAS increases after each uterine surgery, and PAS is a significant concern in those who have had multiple c-section births.

Additional risk factors for PAS include Asherman syndrome; multifetal pregnancy; advanced maternal age; and assisted reproductive technology such as in-vitro fertilization, or IVF.

On physical exam of an unstable patient, there is often profuse vaginal bleeding during attempted placental separation, and the placenta will feel adhered to the uterine wall. Their vital signs will show hypotension and tachycardia, and they often experience altered mental status, look pale, and their skin will feel cold or clammy due to acute blood loss.

Labs may reveal low RBCs and platelets, elevated PT, PTT, and INR, and low fibrinogen as coagulation factors are consumed, but keep in mind that labs may not reflect the degree of blood loss as a hemorrhage can rapidly evolve and it takes time for lab values to reflect that. Therefore, the patient’s clinical picture should serve as an indicator for transfusion rather than lab values.

Additionally, a uterine ultrasound performed at the bedside frequently shows a hypervascular echogenic intrauterine mass suggesting retained placental tissue.

Based on these findings, you should diagnose PAS with postpartum hemorrhage and shock. Now, remember that PAS can cause life threatening hemorrhage, so you shouldn’t delay treatment while waiting for the definitive diagnosis. In fact, while you’re getting your diagnosis, you’re still giving acute management. Continue to monitor your patient closely, provide aggressive IV fluid resuscitation, and prepare to give blood products. Massive transfusion protocols can be utilized to ensure both packed red blood cells and clotting factors are replaced sufficiently. If the patient isn’t already in the operating room, relocate there. If you have time, you can attempt a D&C to remove the placental tissue, particularly if there is only a small area that is stuck. However, if bleeding persists or the placenta cannot be removed, quickly proceed with a hysterectomy.

Okay, time to talk about stable patients who present before delivery. When assessing stable antepartum patients, start with a focused history and physical exam. During the antenatal period, most patients with PAS will not have symptoms, but those with a coexisting placenta previa may present with painless vaginal bleeding in the second or third trimester.

Risk factors are the same as with unstable patients, with the biggest being a prior c-section birth. As a reminder, others include a history of myomectomy or D&C; Asherman syndrome; multifetal gestation; advanced maternal age; and assisted reproductive technology. When it comes to the physical examination, it is often unremarkable.

Here’s a clinical pearl! Although the patient’s physical examination often reveals no unusual findings, do not perform a digital cervical examination if your patient has a known placenta previa, or if the placenta’s location is unknown.