Well that has decided it, I refuse to be on heparin on my next pregnancy! With my non-heparin pregnancies: My dc2 was 2.5hours labour 0-delivery, and dc3 was 1.5hours from 1st contraction to delivery. I can't possibly be on heparin for any future pregnancy, I can't risk getting any quicker!
(I have been on heparin for recurrent MC, but it is not helping, this has definitely helped me to decide to quit taking it!)