eclampsia (ĭklămpˈsēə) [key], term applied to toxic complications that can occur late in pregnancy. Toxemia of pregnancy occurs in 10% to 20% of pregnant women; symptoms include headache, vertigo, visual disturbances, vomiting, hypertension, and edema. The four categories of hypertension during pregnancy are pre-eclampsia, eclampsia, chronic hypertension, and transient hypertension. Pre-eclampsia, which occurs late in pregnancy, is characterized by decreased cardiac output and increased blood vessel resistance. It may be prevented with calcium supplements and low-dose aspirin, and a cesarian section is often safer than natural childbirth. Only 5% of of women with pre-eclampsia progress to eclampsia, which is accompanied by convulsions and coma. To avoid renal and cardiovascular damage of the mother and to prevent fetal damage, the condition is treated by termination of pregnancy.