Dogs can get many types of worms like heartworm, roundworm, tapeworm, whip worm, hookworm, flea tape worm, etc. Ideally, dogs should be worms during pregnancy. This will not allow transmission of worms in to unborn puppies.
Nursing dogs should also be wormed because puppies are more prone to get worm infestation from the mother. Now safe medicines for worms are available that can be used in pregnant and nursing dogs. Majority of the owners are not professional and don't know which medicines are safe and have less side effects. Only vets are professional and can help you a lot. So, if your dog is nursing and you want to treat worm infestations then get advice from vet.
Nursing dogs should also be wormed because puppies are more prone to get worm infestation from the mother. Now safe medicines for worms are available that can be used in pregnant and nursing dogs. Majority of the owners are not professional and don't know which medicines are safe and have less side effects. Only vets are professional and can help you a lot. So, if your dog is nursing and you want to treat worm infestations then get advice from vet.