Pre-eclampsia (previously called toxemia) is a hypertensive disorder of pregnancy. It is defined to exist when a pregnant woman with gestational hypertension develops proteinuria. Originally, edema was considered part of the syndrome of pre-eclampsia, but presently the former two symptoms are sufficient for a diagnosis of pre-eclampsia.
Pre-eclampsia is much more common in the first pregnancy (3-5% of births) and usually becomes evident in the third trimester (and virtually always after the 20th week of pregnancy). It is also more common in women who have preexisting hypertension, diabetes or renal disease, and in women with a multiple gestation (twins, triplets and more).