oh its such a tough decision isn't it? So glad your son is fine now. :)
My DS was born at 24 weeks, at the time we had no explanation but with hindsight it was cervical incompetence. We ummed and aahed about a second child, saw a consultant and agreed a plan should I get pregnant, and went ahead. I fell pregnant and was so incredibly nervous about having a trans vaginal stitch at 12 weeks and progesterone, and possibly 6 months of bedrest with a toddler in tow, but i the back of my mind there was the possibility of not getting to a viable gestation, or having another very early baby who struggled and either didn't make it or ended up with significant disabilities.
Well, at about 6 weeks pregnant I heard of a different procedure and completely changed our minds about the plan - I got a trans abdominal cerclage done privately. I've been ranting all over bliss and mumsnet about them ever since, as they pretty much fix cervical incompetence permanently. Google abbyloopers and have a look.
It sounds like you have more issues though, and that type of stitch might not be appropriate given your uterine scarring - its something you'd have to ask an expert doctor (not your usual NHS consultant who is unlikely to have a clue). On the Abbyloopers site there are some american doctors who offer advice online and i'm sure one would be happy to talk to you on the phone about your circumstances (might want a fee for their time though?).
I think you need to weigh up the different outcomes - what if it all went well? what if you were on bedrest for your pregnancy? what if you had an earlier baby who didn't survive? what if you had a child with severe brain damage due to prematurity? would you be happier to have tried and lost a child than never tried? to have any child regardless of likihood of disability or is it important to have a good chance of a healthy child? These are really personal and thorny questions that only you and your DP can answer, there is no right or wrong one-size-fits-all decision here.
The only other thing i'd say is research, research, research. Can you find other women in the same situation as you? What have their outcomes been? Can you speak to a variety of consultants about this, even if it means paying for a private second opinion?
For us, we decided to go ahead because we were likely to make it to viability with the right sort of care, even though we might end up with another premmie who had some problems the likelihood of a severely damaged child was low and we were prepared to welcome a child even in the worst of health rather than never have another one. But it was a very hard decision to make, and I'm so glad we later found a medical route that could give us a 95%+ chance of getting to term rather than the 70% chance of getting to viability that our first care plan brought.
Good luck making the decision, and I hope you can get the information you need. xxx