Always get pre-op blood work done, it can be indicative of underlying medical issues. Her size (4lbs) shouldn't be a problem, smaller yorkies are routinely spayed with no complications.
Why are you choosing to alter your female first? I would think given their ages your male should be altered first, as he is fully mature. I would wait until closer to one year of age to spay the female, as she isn't fully mature yet. Holding off spaying her for now, would allow her time to grow more, if her size is that much of a concern for you.
__________________  ~Ruby, Reno, Razz, & Jack~ |