Placental mesenchymal dysplasia: An underdiagnosed placental pathology with various clinical outcomes.

BACKGROUND: Placental mesenchymal dysplasia (PMD) is a rare vascular and connective placental anomaly, which is often associated with severe fetal and/or maternal complications. The diversity of presentation of PMD challenges diagnosis and effective pregnancy management.

OBJECTIVE: We aimed to review cases presenting at 7 tertiary centers worldwide over the last decade and to study the occurrence of obstetric and neonatal complications.

STUDY DESIGN: Pathology databases from 7 tertiary hospitals were screened for cases of PMD (between 2007-2017). Pregnancy history, outcomes and ultrasound images were then reviewed for each case.

RESULTS: Twenty-two cases of PMD were identified. Mean gestational age at diagnosis was 23 weeks (16-39 weeks). Prenatal biochemical screening was abnormal in 8 cases (36%). Of the 12 cases that underwent invasive genetic testing, 4 were abnormal. Six patients (27%) developed maternal complications (preeclampsia/gestational hypertension). Fetal growth restriction was identified in 11 cases (50%) and fetal death in 4 (18%). Four (18%) pregnancies were terminated, 9/14 (64%) delivered preterm and only three (14%) progressed normally. Fourteen babies were born alive; 5 (35%) died in the first sixty-one days after birth, 5 (35%) had transient thrombopenia and 1 (7%) had developmental delay at last follow-up. Our series identified four potential new associations with PMD: placental triploidy mosaicism, CHARGE syndrome, fetal pleuropulmonary blastoma and fetal skeletal dysplasia.

CONCLUSIONS: PMD was substantially under-diagnosed before delivery in this cohort. Sonographers, fetal medicine specialists, obstetricians and pathologists should all suspect PMD in cases of an enlarged placenta and should look for fetal abnormalities. Diagnostic genetic testing should be discussed to exclude partial molar pregnancy. Close pregnancy follow-up is indicated due to the high risk of associated fetal or maternal adverse outcomes.