Placental Accreta Spectrum Disorders (PAS)



Incidence, risk factors and perinatal outcomes for placenta accreta in Australia and New Zealand

Cynthia M Farquhar, Zhuoyang Li, Sarah Lensen,Claire McLintock, Wendy Pollock, Michael J Peek, David Ellwood, Marian Knight, Caroline SE Homer, Geraldine Vaughan, Alex Wang, and Elizabeth Sullivan

Placenta accreta is an uncommon condition occurring during pregnancy which is characterised by abnormal placentation. The severity of abnormal placentation can be suspected by ultrasound and MRI and classified into three grades based on histopathology: the least severe and most common presentation is placenta accreta, in which the placental villi penetrate only to the surface of the myometrium. Placenta increta is characterised by invasion of placental villi into the myometrium. The most severe form is placenta percreta, characterised by invasion of villi beyond the myometrium to the uterine serosa and in some cases involving adjacent organs such as the bladder.1 The term ‘placenta accreta’ refers to all three conditions in this paper. Placenta accreta is associated with major pregnancy complications such as massive blood loss and hysterectomy and is potentially life threatening. Once the diagnosis of placenta accreta is established, the decision about mode of birth requires multidisciplinary team planning and often involves complex surgery or radiological interventions to reduce maternal and neonatal morbidity.



Placenta accreta spectrum disorder is a general term to describe a serious but rare complication of pregnancy when part of the placenta, or entire placenta invades and is inseparable from the uterine wall causing severe blood loss after delivery. After giving birth the placenta should separate completely from the uterus. If part or all the placenta remains attached, it is called placenta accrete spectrum disorder. It is also possible for the placenta to invade the muscles of the uterus (placenta increta) or grow through the uterine wall, sometimes extending to nearby organs (placenta percreta).


It usually shows no signs or symptoms in pregnancy although sometimes there is vaginal bleeding in the third trimester.  It can be suspected by a ultrasound scan. If it is detected during pregnancy an early c- section delivery followed immediately by a hysterectomy is likely to be required. Mothers that have placenta accreta are more likely to have their babies born preterm and be admitted to NICU.

Placenta accreta cannot be prevented.

The risk factors for Placental Accreta

  • Previous caesarean delivery with the risk increasing with number of deliveries.
  • Advanced maternal age
  • Prior uterine surgeries
  • Placenta Position – If the placenta covers or partially covers cervix.



Placenta Accreta Spectrum disorders can range from mild to severe. Once it has been diagnosed the doctor can create a plan for the safe delivery of the baby. The mother should recover completely if it is diagnosed and treated properly.  Some cases require a hysterectomy once the baby is delivered to prevent serious blood loss. This kind of birth trauma could cause women to develop Depression and Anxiety so it's important for mums to talk to their doctor for advice and where to find help and information.


Useful Links

Westmead Hospital, NSW - Fact Sheet Placenta Accreta

COPE – Centre for Perinatal Excellence

Through the Unexpected – Perinatal Diagnosis

Panda - Perinatal Mental Health


Confirmation Content

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