You have just as much chance of tearing as someone who never has. I had a bad 3rd degree tear with DS. The surgery went well and they are letting me choose whether I want a natural birth or a c section this time, if the surgery hadn't gone as well as it did and I hadn't healed as well as I did, they would recommend a c section. The registrar did say that I had no more chance of tearing than any other woman giving birth, which I felt was quite reassuring really.
First labour was fast (5 hours) with a big baby (7 pounds 5 ounces 5 weeks early) and I did tear - a lot.
Second later was slightly longer (5 hours) with an even bigger baby (8 pounds 13 ounces) and I only had one tiny tear in a different place. The older tears that were stitched the first time round held fast.
Not sure if that helps, but the general gist is that I had less tears with a bigger baby.
DS1: 7lbs 9oz, 3rd degree tear after epis. and ventouse, 12 stitches both internal and external repaired in theatre with a spinal block
DS2: 7lbs 7oz, 1 stitch at the original wound to tidy up the mess left by his brother according to my MW who spent ages humming and haaing about whether to stitch or not and in the end had to get a second opinion. He actually did the damage with his shoulder rather then his head and the MW was really cross as she was sure we'd manage to avoid a tear totally
DS2 was a fabulous birth - too fast to get into the water - but virtually unassisted by the mw who just let me get on with it.
I had second degree tears with all three births, as did my sister with her three DCs - we were told that it's not the size of the baby (all our babies were small, the largest was 7lb 3) but the speed of the birth (they were all fast) and your 'shape', whatever that means! I can imagine the speed of the birth makes a difference - for DC3 in particular, I did everything to try not to tear, didn't push, mw supported me etc but he shot out and I had no chance to control it.At least it meant that the birth itself wasn't that painful.
Best of luck - I always dreaded the tearing and stitches but it was never as bad as I imagined.
Starlight I think it depends on the degree of tear. I don't think having a 3rd or 4th degree tear stitched in theatre would be the best part of any birth . I certainly found it more traumatic than the difficult birth and that was with the epidural still working.
I was told by my midwife that it depends on why you tore the first time. If you have a particularly friable perenium (not sure what that means) then you are likely to tear again as it's the way you're made, but if you had an instrumental birth then you may be less likely to tear as that's just due to the situation and as long as you have a good birth the next time round you should be fine.
My MW also said its down to how stretchy a persons skin is, some are more than others (maybe thats what friable perenium means). I'm hoping as my first birth was an instumental one, it means that I won't necessarily tear again.
Starlight, yes, I'm worried about it. Had 2nd degree tears last time which took 12 weeks to heal and caused me a lot of pain for much of that time. I think you were lucky that they didn't bother you afterwards, most people aren't that lucky.