This leaflet is to help you understand what Placenta Accreta Spectrum Disorder is, what tests you need and the implication of being diagnosed with Placenta Accreta Spectrum Disorders for your baby and your family.

What is Placenta Accreta Spectrum (PAS) Disorder?

Placenta accreta spectrum disorder (PAS) is a complication of pregnancy where the placenta attaches to the wall of the uterus (womb) in an abnormal way. The placenta is the organ that provides oxygen and nutrients to the developing fetus. Normally the placenta attaches quite superficially to the wall of uterus but, in PAS, the placenta adheres or invades in an abnormal way during the first trimester of pregnancy, pushing too deeply into the uterine wall (myometrium).

There are roughly three parts to the spectrum defined according to the depth the placenta invades into the myometrium:

- Placenta accreta: the placenta adheres too deeply to the uterus but does not invade it;

- Placenta increta: the placenta penetrates deeply into the uterus and invades the uterine wall;

- Placenta percreta: the placenta invades the uterine serosa, i.e. the outer layer of the uterus, and sometimes goes beyond the wall of the uterus to invade adjacent organs such as the bladder.

How does a PAS happen?

PAS disorder occurs in around 1.7 per 10,000 pregnancies; the incidence increases with the presence of risk factors. Risk factors for PAS include: advanced maternal age, multiparity, previous uterine surgery including curettage, assisted reproductive techniques and previous caesarean delivery. The most commonly described risk factor is the association of previous caesarean delivery and low-lying placenta or placenta previa.

Should I have more tests done?

In case of suspicion of PAS, you will be referred to a center with expertise for prenatal diagnosis of PAS. The prenatal diagnosis consists of an ultrasound, performed especially for the evaluation of the uteroplacental interface, the area where the placenta attaches to the uterine wall. This ultrasound should be performed with full bladder and, in some cases, magnetic resonance imaging can also be used.

What are the risks for me at delivery?

This abnormal adherence of the placenta prevents the normal separation of the placenta at the time of delivery and is at high risk of severe post-partum hemorrhage. In some cases, especially with partial placenta accreta, there may be no clinical consequence at delivery. 

How are PAS disorders managed?

Management of PAS disorders may differ depending on your specialist center and the degree of invasiveness of the placenta. Some centers perform a caesarean-hysterectomy, where the uterus (womb) is removed during a cesarean delivery of the baby. Other centers use conservative management, where the placenta is left in the uterus until its complete reabsorption. The best management is the one you decide with your expert center. Generally, the management of PAS consists of a planned caesarean delivery under general anesthesia.

What does it mean for my baby after it is born?

PAS disorders do not usually affect the fetus if placental function is preserved. The possible consequences for your baby are related to moderate prematurity, if caesarean delivery is performed before term, and the risks of general anesthesia. In many cases, delivery will be planned for 35 weeks’ gestational age. In some cases, delivery may need to take place earlier.

Will it happen again?

The recurrent risk for a future pregnancy is around 22% to 29% if uterus was conserved.

What other questions should I ask?

  • What type of PAS is it?
  • Where should I deliver?
  • When should I deliver?
  • Will I have a caesarean?
  • Will I have a general anesthesia?
  • How is PAS managed in the center?

Last updated: September 2019