What is the management approach for a pregnancy with a placental lake?

Management of Placental Lakes in Pregnancy

Placental lakes are generally benign findings that do not require specific intervention or change in routine prenatal care in most cases.

What Are Placental Lakes?

Placental lakes are sonolucent or hypoechoic areas within the placenta that represent physiological dilations of intervillous spaces filled with maternal venous blood. They are typically identified during routine ultrasound examinations in the second or third trimester.

Clinical Significance and Risk Assessment

• Placental lakes are found in approximately 2.2% of pregnancies 1
• Most placental lakes are benign and do not affect pregnancy outcomes
• However, large placental lakes (>2cm × 2cm) may require additional monitoring as they have been associated with:
  • Small-for-gestational-age fetuses 2
  • Rarely, severe fetal growth restriction 3

Differential Diagnosis

When placental lakes are identified, it's important to distinguish them from other placental abnormalities:

• Placental lakes: Typically have smooth borders and no internal echoes
• Placental lacunae: Multiple, irregular, often turbulent flow patterns; strongly associated with placenta accreta spectrum disorder 4
• Placental tumors: May have mixed echogenicity or solid components
• Subchorionic hematomas: Usually located between the placenta and uterine wall

Management Recommendations

For Typical Placental Lakes:

1. Routine prenatal care

   • No change in standard prenatal visit schedule
   • No need for additional ultrasound examinations beyond routine care
   • No activity or pelvic rest restrictions necessary

2. Documentation

   • Record the size, location, and number of placental lakes
   • Note any changes in subsequent ultrasound examinations

For Large Placental Lakes (>2cm × 2cm):

1. Increased surveillance

   • Serial ultrasound examinations to monitor:
     • Fetal growth parameters
     • Amniotic fluid volume
     • Placental appearance and lake size

2. Fetal growth assessment

   • Consider growth scans every 3-4 weeks
   • Assess for signs of fetal growth restriction 2

3. Delivery planning

   • No need to alter timing or mode of delivery based solely on the presence of placental lakes
   • Standard obstetric indications should guide delivery decisions

Special Considerations

When to Suspect Placenta Accreta Spectrum:

If placental lakes are accompanied by any of the following findings, consider placenta accreta spectrum disorder:

• Multiple irregular placental lacunae with turbulent flow 4
• Loss of clear retroplacental space
• Thinning of myometrium (<1mm)
• Abnormalities of uterine serosa-bladder interface 4
• History of prior cesarean delivery with placenta previa 5

In these cases, referral to a maternal-fetal medicine specialist and delivery planning at a level III or IV maternal care center is recommended 5.

Rare Complications:

In very rare cases, extremely large placental lakes may be associated with:

• Reversed middle cerebral artery end-diastolic flow 3
• Severe fetal growth restriction
• Placental insufficiency

Conclusion

Most placental lakes are incidental findings that do not require specific management or intervention. Large placental lakes warrant closer monitoring for fetal growth. The key is distinguishing benign placental lakes from more concerning findings such as placental lacunae associated with placenta accreta spectrum disorder.