At What Age Can I Give My Newborn Puppies Flea Bath?

You can not. It can make them and the mother very ill. If this is a really dire situation you can try a warm bath with very small amount of mild soap. Like ivory. The mother must be washed also. Everyone must be rinsed, and dried very well. If you can, move all to another location so you'll be able to treat "home" while your bathing everyone. Remember, the puppies will suckle nearly anything, be very careful. If your terribly worried call your local SPCA for advice.