Placenta percreta

Placenta percreta is a term given to the most severe but least common form of the spectrum of abnormal placental villous adherence, where there is a transmural extension of placental tissue across the myometrium with a serosal breach. It carries severe maternal as well as fetal risks.

The milder end of the spectrum of abnormal placental villi adherence are:

• placenta accreta
• placenta increta

Epidemiology

It represents ~5% of all types of abnormal villous adherence. The incidence is thought to be increasing, probably due to the increasing practice of cesarean sections (which is a risk factor).

Risk factors 

• prior cesarean section
• placenta previa
• advanced maternal age
• uterine anomalies
• intrauterine adhesion bands
• previous surgery

Pathology

It is characterized by transmural extension of placental tissue across the myometrium with a serosal breach. Placental invasion of the myometrium is related to a thinned decidual endometrium at the site of implantation and this can happen for a number of reasons.

Radiographic features

Ultrasound

Ultrasound may identify:

• protrusion of placental tissue beyond the outer confines of the uterine myometrium
• increased vascularity between serosa and adjacent structures such as the bladder

Treatment and prognosis

Surgical intervention is a mainstay of treatment in most cases. However, bleeding during the intervention is a serious concern especially in a situation where adjacent organs such as bladder or bowel are involved. In these circumstances, conservative management is preferred. Embolization techniques have also been used in selected cases.

Complications

• uterine rupture
• catastrophic peripartum hemorrhage