No, this shouln't be considered when this person goes to trial.
I totally agree, that if this woman was 3 months pregnant, thus making you think she was probably intending to keep the baby, you'd be inclined to think it a double murder, but I think it would lead to too much confusion, legally. Causing a precedent is a very delicate matter. As WM said, what if you accidentaly caused a woman to miscarry, obviously not knowing she was pregnant? you would be tried for murder then...
It's a very complicated and sensitive issue. All I can say is, I hope this psycho is caught soon, and tried for his crimes. God bless the victims.