Around 90 people attended the ceremony and some bought baby shoes for a boy and a T-shirt with a picture of a boy on the front.
The invitations were hand delivered and the theme was Richie's favourite "The Wizard of Oz."
Richie and her boyfriend Joel Madden had revealed the pregnancy in July and she is due in January.
"They're so excited. They can't wait to meet their little baby," said a friend.