Why Does Preeclampsia Raise Blood Pressure and Spill Protein?

Kathryn Gray says both the hypertension and the proteinuria of preeclampsia come from an angiogenic imbalance. She describes the classic model, and she notes it may not be true for everyone. The trouble starts early in pregnancy, when the placenta has to rebuild the mother's blood supply.

Placental trophoblasts should invade the maternal spiral arteries and let them become wider, lower-pressure vessels that supply the placenta with adequate blood flow. If the invasion is not adequate, the placenta develops some degree of hypoxia. The placenta then releases an anti-angiogenic factor into the maternal circulation. The factor soaks up VEGF, a growth factor that maintains endothelial cell function in vessel walls. The same loss hits endothelial cells in the mother's vessels and endothelial cells in the glomerulus of the kidney.

The shared damage to the vessel lining and the kidney filter is how high blood pressure and protein in the urine show up together.