The placenta is supposed to peel off decidua. In accreta, the decidual plane is missing, so the villi grip myometrium and hemorrhage when pulled.
The anchor: After delivery, the placenta will not separate. If oxytocin and traction make bleeding worse, stop thinking atony and start thinking abnormal adherence.
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Accreta Risk Calculator
Tick the patient's risks. The cumulative percentage climbs live. Cross the threshold and the management plan flips to MRI + cesarean hysterectomy team.
Estimated Risk0%
Baseline · routine prenatal care
Routine OB visits. Standard 20-week anatomy scan. No accreta-specific surveillance needed unless previa develops.
From the Attending
The two anchors that double the score every time: placenta previa and number of prior cesareans. Previa + one prior C-section is 3%. Previa + three prior is 67%. That math is the entire counseling visit. Suspect it → MRI, deliver at 34−36 wks at a center with massive transfusion and GYN-onc backup.
THE VISUAL ANCHOR
Accreta Is A Missing Peel Plane
Do not memorize a definition. Watch the plane fail: decidua missing, villi anchored, placenta retained, hemorrhage follows.
The Missing Peel Plane
After DeliveryRetained placenta plus hemorrhage. Placenta will not separate. The clue is timing: postpartum.
Before DeliveryPrevia = painless 3rd-trimester bleeding. Abruption = painful rigid uterus before delivery.
Risk FactorsPrior C-section plus placenta previa over the scar = highest-yield accreta setup.
From the Attending
Placenta accreta is a defective decidua basalis · the villi grow straight into myometrium because there's no decidual stop sign. Three depth levels: Accreta · villi touch myometrium (most common, ~75%). Increta · villi INVADE myometrium. Percreta · villi PERFORATE through serosa (worst, may invade bladder). Top risk factors: prior C-section + placenta previa over the scar · this combination is the boards' favorite setup. Stem says "previous C-section + painless 3rd-trimester bleeding + ultrasound shows loss of clear zone between placenta and myometrium" → accreta until proven otherwise. Delivery plan: planned C-hysterectomy at 34·36 wks at a tertiary center; do NOT attempt manual placental removal · massive hemorrhage.
RISK METER
Prior C-Sections → Accreta Risk
Each prior C-section scars the lower segment. More scar = less decidua = higher accreta risk. Tap each step.
0.24%
0.24% baseline risk with no uterine scar. The decidua heals normally, providing a clean peel plane at delivery.
CLINICAL REASONING
Antepartum Bleeding Decision Tree
A stem says "3rd-trimester vaginal bleeding." Work through the tree to reach the diagnosis.
INTERACTIVE
Sort The Bleeding Pattern
Every answer choice becomes easy once you sort by timing: refuses to detach, detaches too early, or sits in the wrong location.
Pick a chip, then place it in the correct bucket.
Stays Attached
Separates Too Soon / Wrong Site
BATTLE MAP
Accreta Versus The Decoys
Same organ, different failure modes. The exam hides accreta behind previa, abruption, atony, adenomyosis, and an OMM distractor.
Memory Hooks
Accreta = ACRY: Attached Chorionic villi Refuse to Yield.
Previa is before and painless. Abruption is before and painful. Accreta is after and attached.
Accreta, increta, percreta = at, in, through.
FOUR-PATTERN DRILL
Same Organ, Four Failure Modes
Pick a pattern. Work the chain. Each answer locked until you earn it.
ELIMINATION GAME
Find The Cause
The stem gives postpartum retained placenta. Cross out anything that bleeds before delivery or only explains pain.
Retained Placenta Round
Postpartum hemorrhage, failed placental separation, normal coags, and no laceration.
Eliminate the distractors until the right answer is the only one standing.
Defective decidua
Missing peel plane
Adenomyosis
Endometrium in myometrium
Previa
Low placenta
Abruption
Early detachment
Sacral flexion
OMM pain distractor
From the Attending
Three antepartum bleeding patterns to distinguish: Placenta previa · painLESS bright red 3rd-trimester bleeding, normal tone, no fetal distress (initially). Don't do digital cervical exam. Ultrasound diagnoses. Placental abruption · painFUL bleeding + rigid/tender uterus + fetal distress + DIC risk. RF: HTN, cocaine, trauma, smoking. Accreta · picture often quiet during pregnancy but placenta won't deliver postpartum → hemorrhage when you tug. Vasa previa = ruptured fetal vessel → fetal exsanguination with rupture of membranes, rare but tested. Painless = previa or vasa. Painful = abruption. Postpartum stuck placenta = accreta.
BOARD-STYLE WALKTHROUGH
Clinical Vignettes
25 original clinical cases. Answers shuffle each round. Front-side exam tools work before reveal.
