19 week old puppy weight

Question
My German Shepard is a 19 week old female, who is not spayed. (but will be in two weeks) She weighs a little under 35 pounds. I feed her the Science Diet large breed puppy food that my vet recommended. She eats 3 cups of food per day, spread out over 4 meals. I don't think my vet has too much experience with GSD's though that is just my guess. As this is my first GSD, I was wondering if she is too small? Her mother was not very big, yet her father was quite large...

Answer
She may turn out to be on the small side for a Shepherd.  I would switch her to an all life stages food such as Iams, but other than the price, it may not be that much different, and not worth upsetting your vet.  Do resist any suggestions of supplements, especially calcium.  1.5% or more calcium in the diet is one of the worst things for large breed dogs.  Compare her body condition to  http://www.longliveyourdog.com/twoplus/RateYourDog.aspx  Young Shepherds often refuse to eat enough to keep themselves in ideal condition.  If her ribs show a little, try offering her a little more, but don't worry if she won't eat it.  

Check the ends of the leg bones.  If they are still much knobbier than an adult's, the growth plates are still open and it is still growing.  If not, do not expect much more growth.

You may find this link interesting,   http://jn.nutrition.org/cgi/content/full/134/8/2027S

I am glad you and your vet are going ahead with spaying her early.