If you are pregnant and have high blood pressure, swelling of the hands and face, and unexplained weight gain, you may have preeclampsia. This condition is unique to pregnancy and occurs when there is decreased blood flow to the kidneys, brain, liver, retina, and placenta. This dangerous condition occurs in 3 to 4 percent of all pregnancies and is the leading cause of maternal and fetal death in the United States. The only definite cure for preeclampsia is to deliver the fetus.