I mean those medications like aren't good for you. So like it's probably not a great idea to have them pumping through a fetus. That's why they tell you you have to be off the drugs. Not because it's going to stop you from becoming pregnant because it's going to do terrible things to your unborn child if you try to carry it to term and take those medications at the same time

Unfortunately, the DMTs aren't great for a developing fetus. (And there are limits on what clinical trials can be done involving pregnant patients in general beyond MS). There is a group of neurologists who are maybe a bit more knowledgeable about current research on MS and pregnancy than most, but they may still advocate freezing your eggs: https://neuring.org