I had a full term pregnancy after PPROM at 34 weeks, yes! Like you my water broke out of the blue, no warning signs, and they never figured out why. For my second (and last) pregnancy I did the progesterone shots (17P) weekly from my 17th week of pregnancy until my 36th, and then I delivered at 40w3d. Ask about the shots! There's a basic March of Dimes info page on them here: http://www.marchofdimes.com/pregnancy/pretermlabor_progesterone.html
Also, this is kind of random, but it turns out my cholesterol was wicked low-- my total was 111 right before I conceived-- and that's been linked to preterm birth as well (http://www.nih.gov/news/pr/oct2007/nhgri-01.htm). My midwife hadn't heard of it but it makes sense in retrospect-- I was vegan for an eternity, and your body makes progesterone out of cholesterol. It may be worth testing just for the peace of mind. (I was really worried about a second preterm birth my whole second pregnancy-- ugh.) Here's to an easy, full term pregnancy for you.