If Postpartum mood disorders are now considered a major issue both in public health and in psychiatry, the study of maternal Borderline personality disorder (BPD), most often or not associated with peripartum depressive disorder has attracted much less attention. We now know that BPD is common and highly associated with postpartum depression (Apter et al, 2012). This constitutes a high risk group where both mothers and infants are at relational and psychiatric risk; mothers do not acknowledge their mental health issues and therefore do not seek and receive care, whereas their emotional dysregulation negatively impacts interactions. Distorted interactive configurations organize as early as three months postpartum. Mothers show major difficulty in responding to infants and in turn, infants react with dysregulated and/or dismissive behaviors thus reinforcing the risk for an increase of intrusive and inappropriate response from the caregiver. Rapidly mothers and infants seem off beat. At one year, the infants are at high risk of presenting insecure attachment thus heightening their risk of developing future psychopathology. How to recognize, and intervene with these populations will be presented using videos as illustration and tailored management in a perinatal and infant/toddler unit.