in female mammals that have not had offspring, theres sometimes a phenomenon called phantom pregnancy with physical and behavioral changes mimicking real pregnancy. they can go full psycho like this.  in humans, women who have phantom pregnancy are usually at the latter end of normal reproductive life, and are often frustrated or in grief because of their inability to conceive, or because they have lost the object of their love (whether a child or a lover.)   /phantom-pregnancy-in-humans-and-ot her-mammals.aspx
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