Case This 32 year old primigravida with no risk factors had ultrasound scan at 15 weeks which showed abnormally thick placenta with cystic spaces suggestive of partial molar pregnancy with normal fetus. Her AFP was elevated and chromosomal analysis of placental biopsy showed 46XX/XY with only paternal alleles in 46XX, and amniotic cells had normal 46XY karyotype. Pregnancy was continued with close monitoring. Live male infant of 1.02 kg was delivered by caesarean section at 31+2 days in view of fetal growth restriction, oligohydramnios, pre-eclampsia with abnormal liver function tests. Placental section showed significant admixture of abnormal focal enlarged and stem villi with focal cystic degeneration and hydropic changes with no evidence of trophoblastic hyperplasia, consistent with diagnosis of placental mesenchymal dysplasia. Chromosomal analysis of multiple placental biopsies confirmed two cell lines with variable ratio and cord and cord blood cells had normal male karyotype.

Comments Placental mesenchymal dysplasia is rare with only 87 reported cases. Most recent theory of etiology is androgenetic/biparental mosacism as in our case. It is associated with growth restriction, Beckwith-wiedemann syndrome and stillbirth. There is no risk of persistent trophoblastic disease. These pregnancies should be closely monitored for development of possible fetal and maternal complications. Placenta should be examined by experienced histopathologist and cytogenetic analysis should be performed. Neonates should be monitored for possible complications and due to uncertainties about long term prognosis particularly in presence of placental mosaicism and chimerism children should have long term follow-up.