I've had several different "kinds" of setons, and my experience is - the only way you're going to understand which kind you have and how it is supposed to heal is to have your doctor draw it for you. It sounds silly - but there's no telling which kind he put in there.
The basic mechanics of the seton, to my understanding and experience, is that it serves to hold
open the pathway so that any infection present can drain. Without this seton, the area may abscess. Once the infection begins to clear, certain drugs including Remicade, are supposed to work from the "inside out". So... theoretically the Remicade should help the hole in your intestine to close, thus cutting off the bad goo from tunneling out into the fistula. With the absence of drainage from the intestine, the fistula tunnel starts to seal itself shut, working from the inside layers of the skin to the outer. As your fistula heals, the seton will most likely be pushed further and further out. I had a tube that you initially couldn't see at all, no trace of it but the outer stitch. As the fistula healed, I had to cut an inch or two off the seton as it's plastic tube started to protrude. Eventually the doc said it was "shallow enough" so he just "popped" the flared end of the tube out and it was done. But, as I mentioned, that's just with ONE kind of seton. There are at least two others that I have had that work differently.
Whether or not to begin Remicade when contemplating a family is a very personal thing here on the forum. We have several members that have had healthy Remicade pregnancies with healthy Remicade babies. Some go off all medication and are lucky enough to experience clinical remission while they're pregnant, often to have it flare up after the baby is born. There are soooo many different scenarios.
With the experiences I had when my crohn's was "fistulizing", if I were still experiencing those symptoms... I would probably opt to go ahead with the Remicade treatments and follow the philosophy that "what's good for mom is good for baby". Risking abscess and infection during a pregnancy would lead to antibiotics and god knows what else - most of which would scare me more than the possibility of the Remicade adversely affecting the baby. But that's just me. This disease involves more "soul searching" than a lot of people initially realize. Only you can decide what is best for you and your future family.
I'm sure others will chime in with their feelings and information. I hope you find the answers you need to make the choices coming your way... and I wish you the best of luck with your future family! We're hoping to try again soon ourselves.