For this game you will need 10 gifts or so. These can be simple dollar-store type gifts, or they can be something more elaborate.
During the time that the mom-to-be is opening her gifts, set a timer for five minutes. WHen the timer goes off, whoever gave the gift the mom is currently opening gets one of the gifts you provided. Then, the timer is reset to 5 minutes again, and the process is repeated.
This game might be easier if you enlist one guest to manage the timer and another to manage the basket of gifts.