Hope you don't mind me replying cause I'm not "IVF" as such.
I am homozygous C677T (the most "severe" version) mutation. I had my DS all fine and dandy without any troubles but then 2 missed miscarriages (after seeing heartbeats etc which is a little unusual) so my ob tested for this. Then I started megafolate and low dose aspirin and now I'm due in 3 months time (natural conception).
I have access to top medical resources through work and I have researched as much as I can about this condition. There is sooo little known about this condition, most of it is guess work on the part of obstetricians still. I suspect from what I can find that I MAY be at slightly higher risk of heart disease as I get older but if I keep an eye on blood pressure/cholesterol/weight then I don't think I have too much to worry about.
I am most interested now to see if this 2nd baby will be much bigger than my first baby, because that might imply that my first bubby had some form of growth restriction from the mutation (I'm not convinced).