Poltergeist. Coven, #9

You never know what will follow you home. While touring a fixer-upper they're considering buying, Samantha and Steven both have bad feelings about the house. Samantha, who is seven months pregnant, feels a wave of energy come over her as Steven and the realtor go down to the look at the basement without her. Deciding to pass on the abandoned house, Samantha and Steven later return home without a second thought about the house. Meanwhile, Kathy has been busy planning Samantha's baby shower with Steven's mother.
It's not until Steven points out Samantha's odd behavior that Kathy begins to notice it too. As the baby shower looms nearer, Kathy is determined to figure out what's going on with her sister before Samantha is the center of attention in front of everyone. When Kathy and Steven consult a medium about what might be going on, they learn that Samantha is very likely possessed by a poltergeist. And with her growing baby in her belly, the evil spirit may prove impossible to exorcise. Poltergeist is the ninth book in the Coven series, which serves as a prequel to the Under the Moon series.