THE CAT CAN GET PREG BY MULTIPLE OTHER CATS. EACH PREG DEVELOPES IT'S OWN AMNIOTIC SACK. THEREFORE THE CAT CAN BE IMPREGNATED BY AN PLAIN OLD ALLY CAT & STILL GET PREG BY A SIAMESE.
UNFORTUNATELY, I LEARNED THAT WHEN I HAD A PREG "FOSTER" SPAYED. A DIFFERENT VET TOLD ME THE DAY BEFORE SHE WASN'T PREGNANT, SHE NEARLY DIED ON ME. HOPE THIS IS USEFUL KNOWLEDGE.