My friends cat had the same problem every time she brought home her new born babies from the hospital. The cat was very anxious when the babies started crying, crawling, walking. The vet perscibed the cat something and the cat spent his days in my friends bedroom away from the kids.
Very slowly my friend introduced the cat to the kids and now the cat is fine. It took awhile and patience.
Every once in awhile the cat has a relapse when the kids are at a new stage in their lives.