Last month, Ashlee's husband Pete Wentz
admitted that the popstar could have their baby "at any point now".
Speaking about her sibling's pregnancy on The Ellen DeGeneres Show, she said: "They're going to have to [induce labour]. It's already developing really quick."
Explaining the different methods they had already used, Jessica commented: "I think she's really just jumping around trying everything right now.
"[They have tried] different foot massages and stuff."