What is the primary symptom that indicates eclampsia?

The primary symptom that indicates eclampsia is a severe headache. Eclampsia is a serious complication of pregnancy characterized by the onset of seizures in a woman who has previously experienced preeclampsia, which is marked by high blood pressure and often protein in the urine. The severe headache commonly associated with eclampsia can signal increased intracranial pressure or neurological changes, which are critical indicators of the condition's severity.

In relation to the other options, sudden weight gain is often associated with preeclampsia and can indicate fluid retention, but it is not specific to eclampsia itself. Abdominal cramping can occur in pregnancy for various reasons and is not a definitive sign of eclampsia. Decreased fetal movement may be a concern in many pregnancy complications but is not a direct symptom of eclampsia. Identifying severe headache as a primary symptom helps in early recognition and intervention, making it vital for healthcare providers to monitor this sign closely in pregnant patients.