Spiru-tein, thinking about using it as a breakfast supplement during my pregnancy. Good idea?

Not needed. This is basically a protein shake with vitamins added. You should be on pre-natal vitamins anyway, so those aren't needed. You dn't need the extra calories or protein if you are eating a good balanced diet. Will it hurt you-probably not. Do you need it-probably not.
Possibly, but... Protein concentrates are expensive and also encourage the incorrect notion that a nutritious meal can be gulped down in a single drink. These all have protein composition that is inferior to egg-white protein, which is less expensive and contains no 'exotic" ingredients. I recommend a breakfast based on it or one of the fresh substitutes available at the grocery store at a little more cost.