Evening Primrose Oil for starting labor?

Has anyone ever used this during pregnancy to jumpstart labor and for swelling and high blood pressure. We are trying natural remedies for starting labor since I am at risk for developing Preeclampsia and then having to induce. I have gained 7 lbs due to water retention and swelling is out of control. I don't want to induce because I've heard labor is harder and could lead to needing a C-Section. I also don't want to use castor oil because I've heard too many bad things about the cramping, diarrhea and vomiting that will occur.