Would my Pomeranian have problems when giving birth when my Tibetan spaniel mated with her??????????
Judging from the pictures, the Tibetan does not look too large for the Pom for giving birth. Still, if she just mated an emergency clinic can provide the necessary treatment to end the pregnancy. If it is too late for that, she can be spayed. Your vet can take x-rays later in the pregnancy to determine if she might need a c-section. However, as soon as this problem is over, have her spayed. Neuter the Tibetan Spaniel as well. Typically, the only big dog/small dog deliveries I have seen in which a C-section was necessary was for very great size differences. I saw one case in which a 70 lb husky impregnated a 25 lb mutt. The idiot owners thought she could give birth. She could not. She came to us only after the puppies had long died in utero and she needed an emergency C-section. This was a sick, sick case. So yeah, most likely your dog will be fine, but still spay, spay, spay.
