baby blues

noun, plural in form but singular or plural in construction

: a feeling of sadness that is experienced by a woman shortly after giving birth, that is typically accompanied by other symptoms (such as mood swings, crying spells, irritability, and insomnia), and that usually lasts less than two weeks : postpartum blues

The so-called baby blues experienced in the days after childbirth are very common. About 70 percent of women are likely to experience mood swings or feel weepy and emotional about the slightest untoward event or remark.

—Jane E. Brody, The New York Times

compare postpartum depression