This case report describes a primipara without documented psychiatric history prior to complicated delivery. Onset of severe insomnia and anxiety was right after childbirth but not treated. Obsessive thinking pattern became more prominent. The patient became depressed and sought psychiatric help four months after delivery. Insomnia was then treated pharmacologically. Anxiety and depression persisted, suicidal ideation emerged, and the patient became confused, indecisive, overwhelmed, and delusional regarding her child's health. Medications for depression and anxiety were started six months postpartum yet were ineffective. The patient's obsessions gradually became fully psychotic and she committed an altruistic infanticide eight months postpartum. Psychiatric hospitalization occurred, followed by a long course of mental, physical, legal, and social rehabilitation. She was minimally responsive to psychopharmacological treatment, which appeared to be partly related to her hormonal dysregulation. Several months into the treatment she gradually started improving and returned to baseline two years later. The Illinois court found the patient not guilty to murder by reason of Insanity.