Since the baby's arrival marks a new generation, compile a list of the baby's descendents into a family tree! Compile these lists using the latest genealogy software or write them out by hand. Chances are there is a family genealogist from both mommy and daddy's side of the family that would love to help on this project.
Present your findings to the expectant mother as a baby shower gift. This idea is perfect for family baby showers.
A family tree painting
An alternate version of this idea has the artist paint a family tree and etch in the names of the parents, grandparents and optional great-grandparents.