Well  my Chi has only had one litter so far and she is 4yrs old. The male I bred her with was a little bigger than her, so i was worried that she would need a C-section. I agree with Chihuahua mom, the female shouldn't be smaller than 4-5 lbs. mine is 5lbs.  well anyway, my Bitsy gave birth naturally to 4 healthy pups. she had no problem at all , she was a very good first time mom. her instincts kicked in immediately. but yes make sure you are there to help just in case. Sometimes, Vets give you the worst case scenario, which most times doesn't happen. So don't get scared, but still be cautious. :) good luck