Pre-eclampsia

Pre-eclampsia is an elevation in blood pressure in pregnant women which is apparently caused by a conflict between the immune systems of the mother and the fetus. It's most common in first time mothers, but can occur in any pregnancy. It usually occurs in the last part of the third trimester, prior to labor, but can occur even after birth.
The condition is not dangerous by itself, but women with the symptoms must be carefully monitored for eclampsia, which is a life threatening condition that can occur in many women who suffer from preeclampsia. Unfortunately, eclampsia does not have any other obvious symptoms, so testing of blood pressure should be routine for any woman close to giving birth.
==As a differential diagnosis==
In Babies & Bathwater, Naomi had three miscarriages and a child that died of Alexander disease. Her kidney and liver functions were impaired with no stroke or blood clots. House started her on Magnesium and Potassium if it was pre-eclampsia. She was diagnosed with Small-Cell Lung Cancer with the effects she was feeling was from Paraneoplastic syndrome and Lambert - Eaton Syndrome. She eventually died while undergoing surgery to remove a pulmonary embolism.
Pre-eclampsia at NIH
Pre-eclampsia at Wikipedia
Pre-eclampsia at Mayo Clinic