I have a Welsh A that has had laminitis and I breed from her. She has no special treatment but I keep an eye on her to ensure she doesn't get too fat & therefore go down with laminitis again.
If you are at all worried have a chat with your vet.
The period that my pony was in foal and nursing she was least sensitive to laminitis.
It's often said that a mare in foal is in less danger as she needs more nutricients and is less probable to overfeed. However it's not a guarantee as I have also heard from mares in foal that got it.
Also, after delivery need to make sure that all afterbirth comes off - could induce laminitis as well.
Last night I went to a lecture held by our vets. The first subject was laminitus and the second subject was getting your mare in foal. They said it was preferable not to breed from laminitic mares because the extra weight of carrying a foal can put more pressure in the hoof and laminitus can also be brought on by stress. I would discuss the matter with your vet (who knows your mare's full history) and evaluate the risks of it causing lami or not.