In PIH an impending sign of eclampsia is:

As you know, severe preeclampsia progresses to eclampsia if not treated promptly,hence symptoms of severe preeclampsia can also be called as indicators of Impending eclampsia. Signs of Impending or Imminent eclampsia/: Headache (severe) Symptoms of severe preeclampsia/ Blurring of vision/flashing lights Symptoms associated with poor prognosis Epigastric pain Brisk deep tendon reflexes and ankle clonus Diminished urinary output (<400 ml/24 hours).