Placenta Accreta Spectrum

A placenta is built to let go. Between it and the uterine muscle sits a layer of decidua, and after birth that layer gives the placenta a plane to peel away along. Placenta accreta spectrum (PAS) is what happens when that plane is missing. Placental tissue attaches abnormally to the uterine wall because of defective development of the normal decidual interface, usually over an old uterine scar, and depending on the depth of involvement it may adhere directly to the myometrium or extend into or beyond it. Now picture what a well-meant pull on that placenta does. There is no plane to separate along, so the tissue tears through maternal vessels, and the bleeding is torrential. That single picture explains most of what follows: why suspicion must come before birth, why delivery is planned at a centre with the right team, why the placenta is usually left attached, and why nobody should try to remove it by hand when accreta is suspected. Never attempt manual placental removal when PAS is suspected. Forceful placental removal can cause catastrophic haemorrhage. The nurse...