Summary

Placental mesenchymal dysplasia (PMD) is a rare disorder of unknown aetiology characterised by placentomegaly, serpiginous surface blood vessels and large cystic villi. Although a mimic of molar pregnancies and other entities, it can be distinguished from them by its association with intrauterine growth restriction or death of a relatively normal fetus and its characteristic histopathology. We report the case of a 20-year-old primigravida who presented at 16 weeks with heavy clotty vaginal bleeding and subsequent miscarriage. The placenta was grossly abnormal and resembled a partial molar pregnancy. PMD was confirmed by microscopic examination. Postmiscarriage, ultrasound revealed enlarged and multicystic ovaries similar to those seen in ovarian hyperstimulation syndrome (OHSS), which returned to normal a few weeks after miscarriage. This is the first report of PMD associated with OHSS, and we hypothesise that the most likely pathogenesis is ovarian stimulation from PMD-derived vascular endothelial growth factor.