Eclampsia is on the most severe end of the preeclampsia disease spectrum. It is characterized by the occurrence of tonic-clonic seizure activity after 20 weeks' gestation of pregnancy not attributable to another cause. The majority of eclampsia seizures occur after 28 weeks' gestation.

Eclampsia is estimated to occur in 0.1%-2.7% of pregnancies worldwide. This wide range in incidence is likely to represent higher occurrence in areas of the world where interventions earlier in the preeclampsia disease spectrum are less readily available and/or access to prenatal care is limited.

Eclampsia can occur antepartum, intrapartum, or postpartum with roughly a third to half of cases occurring antepartum and a quarter of cases occurring either intrapartum or postpartum. Postpartum preeclampsia and eclampsia can occur up to 3 weeks following delivery, but occurrence after the first 2 postpartum days is exceedingly rare.

Related topic: HELLP syndrome