D..
The worse thing you can do is say nothing. The next worse thing you can say is "You can try again soon." It's amazing how many people fit in both of these catagories.
Make a casserole or pot pie and salad, and take it over to her. Tell her that you are sorry for her loss, that you are thinking of her and saying prayers for her and her family. Tell her that you would be happy to help - just let you know what she needs. Perhaps you could offer to come in the next week and clean the bathrooms, vacuum and wash some clothes. Ask if Tuesday works for her. Try to schedule it because she won't be able to pick up the phone and ask...
She'll be going through the physical part of having had a baby, but no baby coming home. And grieving. It will be a lot to get through.
If you know other moms who would be willing to help, perhaps you could put together a calendar and people take turns.