mother becoming aggressive towards babies

Question
My siamese cat has just started showing signs of aggression towards her 3 day old babies. I am pretty sure she is biting them - not just picking them up. She has had a couple of bouts of vomiting (although she has still been eating and drinking), and it was after she left the nest to vomit this morning that she showed signs of anxiety and started biting at the babies.  She is allowing them to nurse at present, but I feel I have to be on constant 'guard' to make sure she doesn't hurt them.  Can you explain why she has become aggressive and what, if anything, I can do?  This is her first litter.  Oh yes, I just thought I should add that I have handled the babies a lot, mainly because she needed a lot of assistance with the birth and didn't know what to do at first. She seemed absolutely fine with this. I wonder if she feels her nest is not private enough (it is in our bedroom), but this is where she chose to have her babies, and she is extremely sociable as a rule, and sometimes frets if she doesn't have company.  Up until now she has appeared fine with everything, so I am wondering why the sudden change?  Can you advise?

Answer
Hi Donna.  I don't think it's because you're handling the babies that she's become aggressive.  Sometimes in nature a mother will just turn on her kittens, and there is no known reason.  In this case, the kittens would have to be removed from the mother and either placed with a foster mother who is lactating if one can be found, or bottle fed.  

However, since mom is vomiting, it's a good possibility she's become aggressive toward the kittens because she's not feeling well.  I know when I'm sick, I can be short-tempered with whoever's around me.  Since the demands of nursing combined with vomiting could leave mom dehydrated awfully quickly, it would probably be a good idea to get her to the vet.  Medications to calm her stomach as well as treat some of the infections that tend to cause vomiting may be given to help her feel better, and you can go from there.

It might be a good idea to get a small can of kitten formula and a bottle while you're at the vet's office just in case mom continues to be aggressive toward the kittens, and you have to separate them and bottle feed them yourself.  The kittens would need to be kept on a heating pad set on low heat, which should be wrapped in a blanket or thick towel, because they're not able to maintain their body temperature for at least 3 weeks.