Just a random thought, but what if you gave a gift to the teacher who is expecting that relates to her pregnancy/baby? Instead of getting her something for her classroom, get her something for being a mommy...it could be anything from an at-home spa kit (lotion, stretch mark cream, shower gel, etc...) to a gift card for diapers or somesuch. That way she still gets a gift to know she's appreciated, but it suits more what she's going to be doing very soon!!
I can't wait to see your finished product you choose to do!