PLACENTAL VASCULAR LAKES

Placental vascular lakes are avillous blood containing spaces in the placenta.

Classification

0 - No lakes seen.
1+ - One to three small lakes.
2+ - Four to six larger, more irregular lakes.
3+ - Many large and irregular lakes throughout the placenta

ULTRASOUND

• Found within the placental tissue.
• Found in 67% of placentas (1), at any stage of gestation from the first half of the pregnancy until term.

• Turbulent blood flow on real time scanning (2,3).

Video clip of Placental Lake

• These are generally regarded as normal variants, although they may occasionally be extremely large and associated with raised maternal serum a-fetoprotein, fetal growth restriction and premature delivery (2-4).

• Two categories may be distinguished by serial ultrasounds:
1. Stable maternal lakes characterized sonographically by the consistency of their appearance on repeated examination. Microscopically they correspond to large avillous areas (caverns) surrounded by normal villous tissue. They are a non-pathological persistence of the placental anatomical structure from early in pregnancy.
2. Variable maternal lakes correspond to the first stage of the development of a placental thrombus. Their size is variable and their reflectivity may change from one examination to another. This occurs as blood coagulation and fibrin deposition lead to intervillous, subchorionic and marginal thrombosis.
• Large echo-free spaces may be found in pregnancies with elevated maternal serum alpha fetoprotein (MSAFP).

REFERENCES

1. Katz VL, Blanchard GF, Watson WJ et.al. The clinical implications of subchorionic placental lucencies. An J Obstet Gynecol 1991;164:99-100.
2. Jauniaux E, Campbell S. Sonographic assessment of placental abnormalities. Am J Obstet Gynecol 1990;163:1650-1658.
3. Jauniaux E, Ramsay B, Campbell S. Ultrasonographic investigation of placental morphology and size during the second trimester of pregnancy. Am J Obstet Gynecol 1994;170:130-137.
4. Janiaux E, Moscoso G, Campbell S et.al. Correlation of ultrasound and pathological findings of placental anomalies in pregnacies with elevated maternal serum alpha-fetoprotein. Eur J Obstet Gynecol 1990;37:219-230.