Intrapartum diagnosis: primary survey
Bluish appearance with neovascularity and placental 'bulge'
Placental tissue seen to have invaded through the surface of the uterus
Excessive abnormal neo-vascularity in the lower segment (particularly with vessels running cranio-caudally in the peritoneum).
‘Uterine window’: uterine scar dehiscence with the placenta visible directly underneath it. Note the surrounding uterine tissue appears relatively normal.
It is vital that PAS is diagnosed appropriately at delivery. We recommend the stepwise technique described by the International Society for Placenta Accreta Spectrum (IS-PAS.org: formerly IS-AIP.org) in their evidence based management guidelines.
Collins SL, Alemdar B, van Beekhuizen HJ, Bertholdt C, Braun T, Calda P, et al. Evidence-based guidelines for the management of abnormally invasive placenta: recommendations from the International Society for Abnormally Invasive Placenta.
Am J Obstet Gynecol. 2019;220(6):511-26.
For initial diagnosis of PAS after laparotomy at stepwise process should be followed:
Step 1: On opening the abdomen the external surface of the uterus and the pelvis should be thoroughly inspected for frank signs of PAS which include:
Uterus over the placental bed appears abnormal (can have a bluish/purple appearance) with obvious distension (a ‘placental bulge’). See example here.
Placental tissue seen to have invaded through the surface of the uterus. This does not penetrate the serosa very often. See example here.
NB Care should be taken not to confuse this with a ‘uterine window’ which is a uterine scar dehiscence with the placenta visible directly underneath it. If it is a ‘uterine window’ the surrounding uterine tissue will appear normal. See example here.
Excessive, abnormal neo-vascularity in the lower segment (particularly with vessels running cranio-caudally in the peritoneum). See example here.
If these are clearly seen, PAS can be diagnosed confidently without recourse to any further procedures (Grade D recommendation).
Step 2: If these are not seen, then the uterine incision should be made according to the level of antenatal suspicion of PAS .
Classification of the severity/grade of PAS should be made according to the FIGO classification.
Jauniaux E, Ayres-de-Campos D, Langhoff-Roos J, Fox KA, Collins S. FIGO classification for the clinical diagnosis of placenta accreta spectrum disorders.
Int J Gynaecol Obstet. 2019;146(1):20-4.