Your wife might be having a mild depression
due to stress about the pregnancy
and her arthritic pain whether she might be able to help out her daughter or not.get regular treatment for arthritis
and reassure her repeatedly that the delivery is going to be alright.Low dose of benzodiazepines for sleep might be enough but get it after consulting a psychiatrist
.if need be,she will be prescribed antidepreesants too.
Avoid leaving her alone,engage her in something all the tjme because loneliness may aggravate the unwanted thoughts.