I did forget to mention there is a blood test they can also do, but if I remember right the female has to be 4 weeks along before they can do the test..
Also just because your male is bigger does not mean he will throw big.. Two of my males are on the larger size 6-7 lbs and they hardly ever throw a puppy large enough for me to keep back.. Do you know the lines in your male and female? If not you might want to get ahold of their breeders and ask them about the background of the bloodlines of your yorkies..
__________________ Melanie~    |