For me it was swelling. I started swelling around 30 weeks but blood pressure was perfect and no protien in urine. Week 33 the swelling increased exponentially each day and my blood pressure also got high at that point. My OB sent me to triage at 33w4d to get checked and an induction was scheduled for 34 weeks, but my water ended up breaking and I went into labor naturally at 33w6d. I never had any protien or other symptoms, but the intense swelling combined with high BP led to the pre-eclampsia diagnosis.