When should delivery be scheduled for a 29‑week pregnant woman with a prior low‑transverse cesarean scar, a low‑lying placenta, and mitral valve prolapse?

Timing of Delivery for a 29-Week Pregnant Woman with Prior Cesarean, Low-Lying Placenta, and Mitral Valve Prolapse

Delivery should be scheduled at 34 0/7 to 35 6/7 weeks of gestation via planned cesarean section, with immediate evaluation for placenta accreta spectrum disorder given the combination of low-lying placenta and prior cesarean delivery. 1

Optimal Delivery Timing

The American College of Obstetricians and Gynecologists recommends delivery between 34 0/7 and 35 6/7 weeks for placenta previa and low-lying placenta, which represents the optimal balance between neonatal prematurity risks and maternal hemorrhage risk. 1 This timing is critical because:

• Before 34 weeks, neonatal morbidity from prematurity is significantly elevated 1
• After 36 weeks, approximately 50% of women with placenta accreta spectrum require emergent delivery due to catastrophic hemorrhage 1
• Waiting beyond 36 0/7 weeks is explicitly not advised given the hemorrhage risk 1

Critical Risk Assessment Required Now

You must immediately evaluate this patient for placenta accreta spectrum disorder. The combination of low-lying placenta and one prior cesarean delivery increases the risk of placenta accreta 7-fold compared to women without prior cesarean. 1 With three prior cesareans, this risk increases 56-fold. 1

Evaluation Steps:

• Perform detailed transvaginal ultrasound to assess placental location and signs of abnormal placentation 1
• Consider MRI if ultrasound findings are concerning or inconclusive for placenta accreta 1
• Assess the exact distance from the placental edge to the internal cervical os 1

Predelivery Planning (Start Now at 29 Weeks)

Multidisciplinary coordination must begin immediately, not at time of delivery:

• Coordinate with maternal-fetal medicine, anesthesiology, neonatology, and expert pelvic surgeons 1
• Notify blood bank in advance due to frequent need for massive transfusion protocols 1
• Plan delivery at a Level III or IV maternal care facility with capacity for cesarean hysterectomy if needed 1
• Optimize maternal hemoglobin now—treat any anemia with oral or intravenous iron supplementation 1

Antenatal Corticosteroids

Administer antenatal corticosteroids when delivery is planned before 37 0/7 weeks to promote fetal lung maturation. 1 Given the planned delivery window of 34-35 weeks, corticosteroids should be given at the appropriate time (typically 1-2 weeks before planned delivery).

Indications for Earlier Delivery

Delivery before 34 weeks is indicated if any of the following develop:

• Persistent or severe antepartum bleeding 1
• Preeclampsia or other maternal comorbidities 1
• Spontaneous labor or rupture of membranes 1
• Fetal compromise 1
• Maternal inability to maintain adequate oxygenation (<90% oxygen saturation) 2

Mitral Valve Prolapse Considerations

The mitral valve prolapse does not alter the timing of delivery for placenta previa, but requires:

• Cardiology consultation for peripartum management
• Endocarditis prophylaxis is generally not recommended for uncomplicated mitral valve prolapse during cesarean delivery per current guidelines
• Ensure anesthesia team is aware for hemodynamic monitoring during surgery

Intraoperative Planning

If placenta accreta spectrum is confirmed, the surgical team must be prepared for:

• Cesarean hysterectomy with placenta left in situ 1
• Never attempt manual placental removal if accreta is encountered, as this causes profuse hemorrhage 1
• Dorsal lithotomy positioning to allow vaginal access and optimal visualization 1
• Making the uterine incision away from the placenta when possible 1

Common Pitfalls to Avoid

• Failure to diagnose placenta accreta spectrum in women with low-lying placenta and prior cesarean can lead to catastrophic hemorrhage 1
• Delaying delivery beyond 36 weeks significantly increases emergency delivery risk 1
• Digital pelvic examination must be avoided until placenta previa is excluded to prevent triggering hemorrhage 1
• Underestimating blood loss risk—ensure massive transfusion protocol is immediately available 1

Surveillance Until Delivery

• Serial ultrasound every 2-3 weeks to monitor placental location and assess for migration 3
• After 28 weeks, avoid moderate-to-vigorous physical activity but maintain activities of daily living and low-intensity walking 1
• Hospitalize immediately if active bleeding occurs 1
• Recognize that one bleeding episode increases risk for subsequent episodes 1