Your doctor's 70% figure is very much in line with what most specialists quote, VBAC success rates generally sit between 60 to 80% for women with one prior caesarean, so you're actually in a decent position. My friend delivered at KKH and said the team there monitors VBAC mothers very closely throughout labour, which gave her a lot of confidence to try. The key thing is that if labour isn't progressing or baby shows distress, they will move fast, so the risk of an unmanaged emergency is much lower than people fear. That said, do have a detailed conversation with your own O&G about your specific scar thickness and labour conditions, because that will give you the clearest picture for your situation.