Postnatal depression is a depression that occurs after childbirth. It can occur at any time during the year after the baby is born and requires care as it is more serious than baby blues.

Postnatal depression affects 15-20% of new mothers. Of these, about 7% will experience significant symptoms of depression in the first three months after delivery; and 19% will experience mild to moderate symptoms.

Studies show that the rate of postnatal depression is generally higher three months after delivery and gradually decreases thereafter. The number of mothers with depressive symptoms without postnatal depression peaked in the period three to six months after delivery (about 41%).
Side note : signs of fatigue can be confused with depressive symptoms.

Postnatal depression requires immediate medical attention. While support from the spouse, friends, parents or support groups is essential, professional assistance is also required. Without treatment, depression can last a long time.

Since treatment is most effective when postnatal depression is detected early, the mother or father who thinks they are suffering from it must talk to a health care professional (doctor, psychologist, clinical nurse…). The professional consulted will determine the appropriate treatment according to the extent of depressive symptoms and mental health problems present before pregnancy.

Treatment
Psychotherapy may be considered for some parents, while others may also require antidepressants for a period of time. This will help the parent suffering from postnatal depression to smile again and fully enjoy their baby.

https://www.statpearls.com/ArticleLibrary/viewarticle/27543
https://www.routledge.com/Overcoming-Postnatal-Depression-A-Five-Areas-Approach/Williams-Cantwell-Robertson/p/book/9781444167504