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I would be very concerned for the pomchi as the pups, if pregnant, may be too big to deliver normally and a C section may be needed. Dogs can go through a false pregnancy in the third stage of heat so it would be advised you have a sonogram done to confirm pregnancy and to see how big the pups are. I would plan ahead with your vet for a possible C section.
Here is more on pregnancy and signs. Keep in mind that dogs going through a false pregnancy will display the same signs.
c section: http://www.petplace.com/dogs/c-section-cesarean-in-dogs/page1.aspx