Cystic placentomegaly on a second-trimester ultrasound

Abstract

Placental mesenchymal dysplasia (PMD) is a rare disorder of the placenta characterized by placentomegaly, cystic vesicles, and dilated chorionic blood vessels. Clinically and pathologically, it closely resembles partial molar pregnancy and complete hydatidiform mole with a coexistent healthy fetus, both of which are associated with malignant trophoblastic disease. PMD, however, has no risk of malignant trophoblastic disease and can result in the birth of a normal fetus, highlighting the need for clinician awareness of PMD in order to avoid unnecessary termination of a viable and potentially healthy fetus.

A Challenging Diagnosis: Placental Mesenchymal Dysplasia—Literature Review and Case Report

“…When facing an enlarged multicystic placenta on ultrasound with a normal fetus, doctors must consider several elements: the maternal serum β-hCG, the maternal serum alpha-fetoprotein (MSAFP), ultrasound Doppler assessment of the blood flow within the placenta, and karyotype [ 12 ]. PMD exhibits normal or slightly increased beta hCG and high MSAFP [ 3 ]; however, 38% of cases of PMDs have an increase in beta hCG levels [ 45 ].…”

“…The cause of PMD is yet unknown, current theories sustaining the idea of either an egg fertilized by two spermatozoa or a maternal nondisjunction error while the first division of a unique ovum and sperm [ 12 ]. The latter theory is the one that is more likely to be close to the truth since PMD lacks trophoblastic proliferation and stromal trophoblastic inclusions [ 4 , 6 ].…”

“…The latter theory is the one that is more likely to be close to the truth since PMD lacks trophoblastic proliferation and stromal trophoblastic inclusions [ 4 , 6 ]. In maternal nondisjunction, the first meiotic division results in one normal cell with both maternal and paternal genes and one with paternal genes only; after additional divisions, these androgenic cells are confined to the placental vessels and membranes in a mosaic pattern interspersed with normal biparental cells [ 12 , 56 ]. The biparental cells from the first meiotic division continue to divide and mature normally, eventually forming the trophoblastic layer that develops into a significant portion of the placenta [ 12 , 56 ].…”

Insights into the role of placenta thickness as a predictive marker of perinatal outcome

“…Placental-related diseases also contribute to sonographically thickened placenta, including placental chorioangioma, chorioangiomatosis, cord angiomyxoma, subamniotic hematomas, placental lakes, and placental abruption. 25,26,46–50 Placenta abruption is one of the most serious complications of pregnancy, and it is commonly associated with premature labor and delivery and higher rates of perinatal death. Sonographic imaging shows retroplacental hematoma and increased PT.…”

“…PMD is characterized by placentomegaly with cystic vesicles, dilated chorionic blood vessels, and mesenchymal hyperplasia without trophoblastic proliferation. 49,50 When a thick placenta is identified, placental-related abnormalities should be considered, especially when maternal and fetal abnormalities are ruled out.…”