T.,
I am so sorry for your friend's loss. You are a wonderful friend for wanting to do something. As another mom said, keep in touch. Even if she doesn't answer the phone, leave a message letting her know to not feel obligated to call back, but wanted to let her know that you are thinking about her.
I also wanted to suggest meals. Either to make them or gift certificates to their favorite restaurants or take out places. We all know how hard it is to cook when we aren't feeling well.
I like the other mom's suggestions of flowers or a donation. Donating to the March of Dimes is a suggestion to help other babies and research for pregnancy loss.
Hugs to you and your friend,
B.