Introduction
Placenta accreta spectrum (PAS) is a group of abnormal placental implantation disorders that represent a leading cause of pregnancy-related morbidity and mortality. This condition occurs when the placenta adheres too deeply to the uterine wall, making delivery complicated and potentially life-threatening.
[Image prompt: Anatomical cross-section diagram showing normal placenta vs placenta accreta spectrum, highlighting the different depths of invasion – accreta, increta, and percreta]
Definition and Terminology
The placenta accreta spectrum encompasses three conditions based on the depth of placental invasion:
- Placenta accreta: Placental villi adhere directly to the myometrium (most common – 75-80%)
- Placenta increta: Placental villi invade into the myometrium (15-20%)
- Placenta percreta: Placental villi penetrate through the myometrium and may involve adjacent organs (5%)
Epidemiology
- Incidence: 1 in 272 pregnancies (2015 data)
- Represents a 10-fold increase since the 1980s
- Associated with rising cesarean delivery rates
- Maternal mortality rate: 7% for placenta accreta spectrum
[Image prompt: Infographic showing rising incidence of PAS correlated with increasing cesarean section rates over decades]
Risk Factors
Major Risk Factors:
- Previous cesarean delivery – Most significant risk factor
- Placenta previa – Especially with prior cesarean
- Advanced maternal age (>35 years)
- Multiparity (≥6 previous births)
Additional Risk Factors:
- Previous uterine surgery (myomectomy, curettage)
- Endometrial ablation
- Uterine anomalies
- Asherman syndrome
- In vitro fertilization
- Smoking
| Number of Prior Cesareans | Risk with Anterior Placenta Previa |
|---|---|
| 0 | 3% |
| 1 | 11% |
| 2 | 40% |
| 3 | 61% |
| 4+ | 67% |
Pathophysiology
The normal decidua basalis acts as a barrier preventing deep placental invasion. PAS occurs when:
- Defective decidualization: Inadequate formation of decidua basalis
- Abnormal trophoblast invasion: Excessive invasion beyond normal boundaries
- Uterine scar disruption: Previous surgery disrupts normal anatomy
[Image prompt: Microscopic histological comparison showing normal decidua vs defective decidua in placenta accreta]
Clinical Presentation
Antepartum:
- Usually asymptomatic
- May present with vaginal bleeding (especially with placenta previa)
- Preterm labor risk
Intrapartum/Postpartum:
- Retained placenta – Unable to deliver after 30 minutes
- Postpartum hemorrhage – Massive bleeding
- Incomplete placental delivery
- Uterine atony unresponsive to uterotonics
Diagnosis
Ultrasound Features (First-line):
- Loss of retroplacental clear space
- Thinning of myometrium (<5mm)
- Lacunar spaces – “Swiss cheese” appearance
- Bridging vessels – Vessels crossing lacunae
- Bladder line interruption (for percreta)
MRI Indications:
- Inconclusive ultrasound findings
- Suspicion of placenta percreta
- Posterior placenta evaluation
- Surgical planning
MRI Features:
- Dark intraplacental bands (T2-weighted)
- Focal bulging of placenta
- Loss of retroplacental dark zone
- Direct contact with bladder (percreta)
[Image prompt: Side-by-side ultrasound and MRI images showing characteristic features of placenta accreta spectrum]
Management
Prenatal Management:
- Multidisciplinary team approach
- Referral to tertiary center with expertise
- Serial monitoring for bleeding and preterm labor
- Corticosteroids for fetal lung maturity if preterm
- Iron supplementation for anemia prevention
Delivery Planning:
- Timing: 34-35 weeks (individualized)
- Setting: Tertiary care center with blood bank
- Team: Maternal-fetal medicine, anesthesia, urology, general surgery
- Blood products: 4-6 units PRBCs, FFP, platelets available
Surgical Management:
Cesarean Hysterectomy (Gold Standard):
- Avoid placental separation attempts
- Deliver baby through fundal incision
- Leave placenta in situ
- Proceed with hysterectomy
Conservative Management:
- For desire for future fertility
- Stable maternal condition
- Partial accreta cases
- Options: Focal resection, uterine artery embolization, compression sutures
| Management Approach | Indication | Success Rate | Complications |
|---|---|---|---|
| Cesarean Hysterectomy | Severe PAS, completed childbearing | 95-100% | Surgical risks, loss of fertility |
| Conservative Management | Desire fertility, partial accreta | 70-80% | Bleeding, infection, repeat surgery |
| Uterine Artery Embolization | Adjunct therapy | Variable | Infection, ischemia |
Complications
Maternal:
- Hemorrhage: Average blood loss 3-5 liters
- Coagulopathy: DIC, dilutional coagulopathy
- Organ injury: Bladder (most common), ureter, bowel
- Infection: Endometritis, sepsis
- Respiratory: ARDS, pulmonary edema
- Renal: Acute kidney injury
- Death: 7% maternal mortality rate
Fetal/Neonatal:
- Preterm delivery complications
- Intrauterine growth restriction
- Respiratory distress syndrome
- Neonatal death (rare)
[Image prompt: Flowchart showing potential maternal complications and their management pathways]
Prevention
- Reduce unnecessary cesarean deliveries
- VBAC counseling when appropriate
- Careful surgical technique to minimize uterine scarring
- Optimize interpregnancy interval (>18 months)
Prognosis
With Appropriate Management:
- Maternal mortality: 0-7%
- Severe morbidity: 20-50%
- Successful conservative management: 70-80%
- Future pregnancy viability: Variable (if uterus preserved)
Key Learning Points
- PAS incidence is rising due to increasing cesarean delivery rates
- Early prenatal diagnosis allows for optimal delivery planning
- Multidisciplinary team approach is essential
- Cesarean hysterectomy remains the gold standard for severe cases
- Conservative management is possible in select cases
- Prevention focuses on reducing unnecessary cesarean deliveries
Conclusion
Placenta accreta spectrum represents a significant obstetric challenge requiring early recognition, careful planning, and multidisciplinary management. Understanding risk factors, diagnostic criteria, and management options is crucial for all healthcare providers involved in obstetric care. The key to optimal outcomes lies in prenatal diagnosis, appropriate referral, and delivery at experienced centers with adequate resources.
[Image prompt: Summary infographic showing the complete management pathway from diagnosis to delivery for placenta accreta spectrum cases]