Placental mesenchymal dysplasia (PMD) is an extremely rare histological condition in which there is massive hydrops of placental stem villi with absence of trophoblast hyperplasia and trophoblastic inclusions. Its reported incidence is 0.02% of all pregnancies [
Mrs. A, gravida 2 with previous one living issue, presented at 17 weeks gestation with spotting per vaginum for one week. Her obstetric and past history was unremarkable. On clinical examination, the fundal height corresponded to 22 weeks period of gestation. Ultrasound revealed a single live fetus corresponding to the period of gestation associated with omphalocele (Figure
Ultrasound: fetus with omphalocele.
Ultrasound: Placentomegaly with multiple large anechoic areas. Is the entity partial mole?
PMD is a rare placental vascular malformation. Fetal omphalocele is another rare anomaly with an incidence of 1 : 3200 to 1 : 40000 [
The exact pathogenesis of PMD association with omphalocele is still unknown. Doubts have been raised about hydrops of placenta as a sequel to umbilical cord obstruction. Interestingly, female predominance has been seen in the literature. There may be a possible relationship between X chromosome and mesenchymal dysplasia [
In clinical practice, suspicion of PMD arises when a patient in second trimester undergoing triple screening shows elevated maternal serum
This condition is commonly confused with partial mole antenatally. The triploid fetus of partial mole may be differentiated on ultrasound by characteristic fetal malformations, such as syndactyly involving fingers 3-4 and toes 2-3, dysplastic cranial bones, and genital anomalies [
A triploid karyotype in partial mole on cordocentesis helps differentiation between two entities. Sonographic findings of PMD can also resemble complete mole with cotwin or chorioangioma [
Postdelivery PMD is characterized by a large placenta with parenchymal vesicle and dilated vessels over its surface and weight usually greater than 95th percentile for gestation. Microscopic examination of placental tissue reveals massive hydrops of stem villi and characteristic absence of trophoblastic proliferation and villous trophoblastic inclusion. Terminal villi may be normal or mildly edematous. There may be chorioangiomatoid change of stem villous or aneurysmal dilatation of stem villous vessels [
PMD is considered prognostically superior to partial mole as a diploid phenotypically normal fetus has better survival rates [
This paper enlists the salient features of PMD for awareness among the ultrasonologists and obstetricians and stresses its identification as a distinct entity.