You know, I know quite a few people that smoke weed during pregnancy b/c they had horrible morning sickness and couldn't ever eat, it helped their appetite and their babies are perfectly fine too;
In fact, they prescribe medical marijuana to pregnant women in some states to help with morning sickness.
The only health risks weed has when your pregnant is that it can make your child more prone to ear infections.
It really doesn't fuck with the baby.
But anything the mother takes in the baby does as well.
Smoking does get to your baby when you are pregnant, once weed enters your bloodstream, it passes through the umbilical chord onto the baby; that's how it works with other drugs even cigarettes too.
But truth be known, if it was so bad for babies, they wouldn't prescribe it to the mother.