This systematic review evaluated the consequences of untreated maternal postpartum depression (PPD) on both mothers and infants. A total of 122 studies were included, with results categorized into three areas: maternal consequences, infant consequences, and mother–child interactions. Maternal consequences included physical health, psychological health, relationships, and risky behaviors. Infant consequences included anthropometry, physical health, sleep, and developmental aspects such as motor, cognitive, language, emotional, social, and behavioral development. Mother–child interactions included bonding, breastfeeding, and the maternal role. The review found that PPD negatively affects both mothers and infants. Maternal PPD was associated with poorer physical health, lower psychological well-being, reduced social relationships, and increased risky behaviors. Infants of mothers with PPD showed poorer anthropometric outcomes, such as lower weight and length, and had higher rates of health issues, sleep problems, and developmental delays. Mother–child interactions were also affected, with reduced bonding and breastfeeding rates. The study emphasized the importance of early detection and treatment of PPD to prevent these negative outcomes. Maternal PPD was linked to increased risks of depression, anxiety, and suicidal ideation, as well as poorer quality of life and social functioning. It also contributed to higher rates of infant sleep disturbances, motor and cognitive delays, and behavioral problems. The review concluded that PPD creates an environment that is not conducive to the development of both mothers and children, highlighting the need for early intervention.This systematic review evaluated the consequences of untreated maternal postpartum depression (PPD) on both mothers and infants. A total of 122 studies were included, with results categorized into three areas: maternal consequences, infant consequences, and mother–child interactions. Maternal consequences included physical health, psychological health, relationships, and risky behaviors. Infant consequences included anthropometry, physical health, sleep, and developmental aspects such as motor, cognitive, language, emotional, social, and behavioral development. Mother–child interactions included bonding, breastfeeding, and the maternal role. The review found that PPD negatively affects both mothers and infants. Maternal PPD was associated with poorer physical health, lower psychological well-being, reduced social relationships, and increased risky behaviors. Infants of mothers with PPD showed poorer anthropometric outcomes, such as lower weight and length, and had higher rates of health issues, sleep problems, and developmental delays. Mother–child interactions were also affected, with reduced bonding and breastfeeding rates. The study emphasized the importance of early detection and treatment of PPD to prevent these negative outcomes. Maternal PPD was linked to increased risks of depression, anxiety, and suicidal ideation, as well as poorer quality of life and social functioning. It also contributed to higher rates of infant sleep disturbances, motor and cognitive delays, and behavioral problems. The review concluded that PPD creates an environment that is not conducive to the development of both mothers and children, highlighting the need for early intervention.