A pregnancy complication is characterized by high blood pressure and signs of damage to another organ system, most often the liver and kidneys. Preeclampsia usually begins after 20 weeks of pregnancy in women whose blood pressure has been normal. Left untreated, preeclampsia can lead to serious — even fatal — complications.
https://www.mayoclinic.org/diseases-conditions/preeclampsia/symptoms-causes/syc-20355745
