Accreta placentation

Placenta accreta spectrum (PAS) disorders describe different grades of abnormal attachments of the placenta to the uterine wall.

It results from a failure of normal decidualization in an area of a previous uterine scar.

• In placenta creta villous tissue adheres directly to the myometrium without invading the uterine wall.
• In placenta increta the villous tissue invades the myometrium.
• In placenta percreta the villous tissue invades the entire thickness of myometrium including the uterine serosa.

The different grades of placenta accreta spectrum disorders may coexist within the same placenta, as illustrated below.