You are lobbing a giant softball over the plate!
Of course veganism is harmful to babies and mothers. And to many adults, too, although apparently not all.
Even the most conscientious vegan faces some health risks. Feeding a baby only vegan foods (even if you include breast milk) is criminal.
EDIT: In the interest of being intellectually honest: I don't deny that veganism may work for some adults and even some mothers/kids. I see some vegan moms insisting that their kids are "perfectly healthy." Well, I'm not sure about that, since my definition of "healthy" seems to be different from theirs (what about allergies, other auto-immune conditions, height/weight, muscle tone, etc.). But anyway, my argument is not that veganism is a death sentence or will automatically lead to sick babies, but as a matter of principle I think that even conscientious and responsible vegans are putting their babies at risk on a strict vegan diet. Not cool.