Since spider angiomas are benign lesions, you should wait until after you deliver your baby to have treatment.
I would not recommend undergoing any laser procedure while you are pregnant. In general, these types of elective procedures are avoided at this time, as their effects on the fetus are largely unknown. At the same time, spider angiomas are benign vascular lesions that can be treated extremely effectively with laser. You can rest easy that there is a good treatment for you as soon as you deliver!