Placental histopathology and correlated clinical outcomes in kidney transplant recipients

Pregnancies after kidney transplantation are high-risk. Whilst previous studies have explored pregnancy outcomes, there are no existing data on the placental histopathology findings of kidney transplant recipients and how these correlate with clinical outcomes. From 1976 to 2020, 62 pregnancies to 37 transplant recipients were identified in a South Australian clinical unit. The medical records were evaluated to identify if placental tissue had been sent for histopathology. The histology was reviewed contemporaneously, blinded to outcomes, following the Amsterdam consensus. The findings were correlated with the clinical data. Placental tissue was referred for histopathological examination in 20 pregnancies to 15 women. A high rate of adverse perinatal outcomes was noted, with fetal growth restriction (FGR; n=6), pre-eclampsia (n=8), worsening renal function with >10% increase in serum creatinine from preconception (n=9), pre-term birth (n=15), and antenatal hypertension (n=12). Maternal vascular malperfusion was seen in 14/20 pregnancies, including in all cases with pre-eclampsia, and was commonly observed with FGR (5/6 cases), decline in kidney function (8/9), antenatal hypertension (7/12) and preterm birth (12/15). In this high-risk population, increased obstetric ultrasound scans with uterine and umbilical Doppler should be considered to monitor and manage maternal uteroplacental vascular perfusion. We recommend all placental tissue from transplant recipients be referred for histopathological examination.