Intrapartum diagnosis: secondary survey

Snowman Sign

The upper segment has contracted but the lower segment has little muscle and so 'bulges' forward

Snowman Sign


Snowman Sign


Secondary Survey

It is vital that PAS is diagnosed appropriately at delivery. The stepwise technique described by the International Society of Abnormally Invasive Placenta ( in their evidence based management guidelines should be used.

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.

Step 1: See Intra-partum diagnosis: Primary Survey

Step1 Post-Partum:

  • After delivery of the baby the upper segment will contract but if there is abnormally invasive placenta the lower segment will bulge forward - often called the 'Snowman sign'.

Step 2:

  • If the incision has been placed such that the placenta is undisturbed, then gentle cord traction should be attempted. If traction on the umbilical cord causes the uterine wall to be visibly pulled inwards in the direction of traction without any separation of the placenta (the ‘dimple’ sign) and there is apparent contraction of the uterus separate from the placental bed, then PAS can be diagnosed (Grade D recommendation).

Step 3:

  • If PAS has not been diagnosed by the previous 2 steps, then gentle digital exploration can be attempted to assess if there is a plane of cleavage.

  • For the diagnosis of PAS, a manual removal of placenta is required and at the time of manual exploration of the uterine cavity, in the opinion of a senior, experienced obstetrician, no plane of cleavage can be identified between the placenta and the myometrium. This can be for the entire placenta bed or just in ‘focal’ areas. Care must be taken to avoid causing hemorrhage.

Classification of Severity

Classification of the severity/grade of PAS should be made and clearly recorded 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.