I attempted treatment with my first pregnancy, but I had extreme morning sickness throwing up 24/7 from week 5 till birth. I couldn't keep meds down if I wanted to. Same with my second so I didn't even attempt it. So no. I wasn't treated.
So yes it is possible to have perfectly healthy babies without treatment. And I have had lyme since 1998. I don't know the statistics, but I have a highly regarded llmd who assured me the risk was low. I can only go from experience, but my girls are 100% healthy.