The cause of eclampsia is not well understood. Eclampsia may follow pre-eclampsia, if that condition cannot be brought under control. Pre-eclampsia is a serious condition which occurs during pregnancy and is marked by high blood pressure, weight gain, and protein in the urine.

It is difficult to predict which pre-eclamptic women may go on to have seizures -- the hallmark of eclampsia. There is poor correlation between the degree of hypertension present in pre-eclampsia and the ultimate occurrence of seizures.

The exact cause of pre-eclampsia has not been identified. Numerous theories of potential causes range from genetic, dietary, vascular (blood vessel), and neurological factors. None of the theories has yet been proven.

Pre-eclampsia occurs in approximately 5% of all pregnancies. The incidence of eclampsia is approximately 1 out of 2000 to 3000 pregnancies. An increased risk for pre-eclampsia is associated with first time pregnancies, teenage pregnancies or mothers older than 40 years, African-American women, multiple pregnancies, and women with a history of diabetes, hypertension, or renal (kidney) disease.