What Causes Flashing Light In Eyes, Dizziness, Numb Lips And Tongue?

35 year old. 36 weeks and 4 days pregnant. with 8th child (6th c-section) sudden onset of flashing beams of light in eyes and severe dizziness with numb lips and tongue. bp normal throughout entire pregnancy and last visit was on 2/20/15. no diabetes but history of mvp (dianosed 18 years ago) but never required any medical treatment.