International Federation of Gynecology and Obstetrics (FIGO) general classification of placenta accreta spectrum disorders
| Grade 1: Abnormally adherent placenta (accreta) | |
| Clinical criteria | |
| At vaginal delivery | No separation with synthetic oxytocin and gentle controlled cord traction |
| Attempts at manual removal of the placenta results in heavy bleeding from the placenta implantation site requiring mechanical or surgical procedures | |
| If laparotomy is required (including for cesarean delivery | Same as above |
| Macroscopically, the uterus shows no obvious distension over the placental bed (placental ‘bulge’), no placental tissue is seen invading through the surface of the uterus, and there is no or minimal neovascularity | |
| Histologic criteria | Microscopic examination of the placental bed samples from a hysterectomy specimen shows extended areas of absent decidua between villous tissue and myometrium with placental villi attached directly to the superficial myometrium |
| The diagnosis cannot be made on just delivered placental tissue nor on random biopsies of the placental bed | |
| Grade 2: Abnormally invasive placenta (increta) | |
| Clinical criteria | |
| At laparotomy | Abnormal macroscopic findings over the placental bed: bluish/purple coloring, distension (placental ‘bulge’) |
| Significant amounts of hypervascularity (dense tangled bed of vessels or multiple vessels running parallel craniocaudially in the uterine serosa) | |
| No placental tissue seen to be invading through the uterine serosa | |
| Gentle cord traction results in the uterus being pulled inwards without separation of the placenta (the so-called ‘dimple sign’) | |
| Histologic criteria | Hysterectomy specimen or partial myometrial resection of the increta area shows placental villi within the muscular fibers and sometimes in the lumen of the deep uterine vasculature (radial or arcuate arteries) |
| Grade 3: Abnormally invasive placenta (percreta) | |
| Grade 3a: Limited to the uterine serosa | |
| Clinical criteria | |
| At laparotomy | Abnormal macroscopic findings on uterine serosal surface (as above) and placental tissue seen to be invading through the surface of the uterus |
| No invasion into any other organ, including the posterior wall of the bladder (a clear surgical plane can be identified between the bladder and uterus) | |
| Histologic criteria | Hysterectomy specimen showing villous tissue within or breaching the uterine serosa |
| Grade 3b: With urinary bladder invasion | |
| Clinical criteria | |
| At laparotomy | Placental villi are seen to be invading into the bladder but no other organs |
| Clear surgical plane cannot be identified between the bladder and uterus | |
| Histologic criteria | Hysterectomy specimen showing villous tissue breaching the uterine serosa and invading the bladder wall tissue or urothelium |
| Grade 3c: With invasion of other pelvic tissue/organs | |
| Clinical criteria | |
| At laparotomy | Placental villi are seen to be invading into the broad ligament, vaginal wall, pelvic sidewall, or any other pelvic organ (with or without invasion of the bladder) |
| Histologic criteria | Hysterectomy specimen showing villous tissue breaching the uterine serosa and invading pelvic tissues/organs (with or without invasion of the bladder) |
For the purposes of this classification, uterus includes the uterine body and uterine cervix.