What is the recommended management for a patient with a previous Lower Segment Caesarean Section (LSCS) who exhibits a crossover sign?

Crossover Sign in Previous LSCS Patients: Management Recommendations

Understanding the Crossover Sign

The "crossover sign" refers to a radiological finding on ultrasound or MRI where the placenta appears to cross over or extend beyond the boundaries of a previous cesarean scar, suggesting potential placenta accreta spectrum disorder (PASD). In patients with previous LSCS who exhibit a crossover sign, immediate referral for specialist imaging with ultrasound Doppler evaluation is mandatory, followed by MRI if ultrasound is equivocal, and delivery planning at a tertiary center with multidisciplinary surgical capabilities including access to interventional radiology, blood products, and ICU support. 1

Risk Stratification

High-Risk Features Requiring Immediate Action

• Previous cesarean section with anterior placenta previa or low-lying placenta represents the highest risk scenario, with up to 40% developing PASD after three prior cesarean deliveries 1
• The absolute risk of placenta accreta increases dramatically: 12.9 per 10,000 after one cesarean, 41.3 per 10,000 after two, 78.3 per 10,000 after three, and 217 per 10,000 after four cesarean sections 1
• Any ultrasound abnormalities at the placental-myometrial interface mandate Doppler evaluation regardless of placental location 1

Diagnostic Algorithm

Initial Imaging Approach

1. Perform comprehensive transabdominal ultrasound as the first-line imaging modality, specifically evaluating:

   • Placental location and relationship to the previous scar
   • Loss of clear zone between placenta and bladder
   • Placental lacunae (irregular vascular spaces)
   • Bladder wall interruption
   • Myometrial thinning at the scar site 1

2. Add transvaginal ultrasound if transabdominal views are inadequate, particularly to visualize the internal cervical os and lower uterine segment 1

3. Apply color Doppler ultrasound to identify abnormal vascularity patterns, which significantly improves diagnostic accuracy (sensitivities 77-97%, specificities 96-98%) 1

When to Escalate to MRI

Order MRI without IV contrast when: 1

• Ultrasound findings are equivocal or nondiagnostic
• Posterior placentation limits ultrasound assessment
• Maternal obesity severely limits ultrasound visualization
• Surgical planning requires precise mapping of invasion depth and laterality
• Assessment of parametrial invasion is needed

Critical caveat: Gadolinium contrast should be avoided in pregnancy unless delivery is imminent or termination is planned, as it crosses the placenta and remains category C 1

Delivery Planning

Timing and Location

• Schedule delivery at 34-37 weeks at a tertiary center with the following capabilities: 1
  • Experienced surgical team including gynecologic oncology or urology if deep invasion suspected
  • Interventional radiology available for potential embolization
  • Massive transfusion protocol and adequate blood product availability
  • Adult and neonatal ICU capabilities

Surgical Preparation

• Pre-operative ureteral stent placement should be considered if lateral or parametrial invasion is suspected on MRI 1
• Arrange for cell saver availability (with leukocyte depletion filter for amniotic fluid contamination)
• Consent patient for possible hysterectomy, bladder injury repair, and massive transfusion 1

Intraoperative Management Modifications

Incision Considerations

• Avoid the Joel-Cohen incision in confirmed PASD cases; instead, use a vertical midline incision for better exposure and vascular control 2
• Plan hysterotomy location away from areas of suspected placental invasion when possible

Critical Surgical Principles

• Do not attempt manual placental removal if accreta is confirmed - this dramatically increases hemorrhage risk
• Consider leaving placenta in situ with delayed hysterectomy in select cases of focal accreta
• Have vascular clamps and packing materials immediately available 1

Common Pitfalls to Avoid

1. Never dismiss subtle ultrasound findings in high-risk patients - even small irregularities at the scar-placenta interface warrant further evaluation 1

2. Do not rely on absence of ultrasound findings to exclude PASD - up to 23% of cases may have negative imaging 1

3. Avoid scheduling delivery at facilities without appropriate surgical and blood bank resources - maternal mortality increases significantly when PASD is managed at non-tertiary centers 1

4. Do not perform cesarean section through an area of suspected placental invasion without having discussed alternative hysterotomy sites with the surgical team 1

5. Never attempt conservative management without explicit informed consent regarding risks of hemorrhage, infection, and need for delayed hysterectomy 1

Postoperative Surveillance

For patients who undergo successful conservative management or have confirmed scar defects:

• Ultrasound assessment at 3 months postpartum to evaluate residual myometrial thickness (RMT), with RMT >8 mm indicating adequate healing 3
• Counsel regarding significantly increased risks in future pregnancies: uterine rupture (22 per 10,000 births), repeat PASD, and need for early first-trimester scanning 1, 4
• Screen for cesarean scar pregnancy in any subsequent first trimester as this dramatically increases PASD risk 1