Within days following birth, most women are showing signs of mood changes, commonly named baby blues. Due to the frequency of this condition, baby blues is considered as a physiological state probably associated to biological modifications. Some studies have shown an existing link between the intensity of the baby blues and post-partum mood disorder. Therefore, it seems important to report and explore in more details the clinical background related the condition. The aim of this study was to demonstrate the possibility of a link between the intensity of the baby blues and some specific factors like maternal self-esteem, maternal childcare stress and social background, and also to define the symptoms of the baby blues from core dimensions in mood disorders. Mothers were recruited few hours before giving birth in a teaching hospital. At the third day following birth, an appointment was made to obtain the necessary information (past medical history and social history) and history of previous mood disorders. The mood was evaluated from the scale of the intensity of baby blues from Kennerly and Gath (1989). Moreover, evaluations at day 3 and week 6 post birth of self-esteem in relation to motherhood (Maternal self-report Inventory from Shea and Tronick, 1988), stress in relation with the care of the baby (Childcare Stress Inventory from Cutrona, 1983) and the social support (Social Support scale from Bruchon-Schweitzer, 1998) were undertaken. 95 women were included in the final sample. The intensity of the baby blues was explained by the type of pregnancy (p=0.002), a low maternal self-esteem (p=0.025), high levels of stress in relation to the care of the baby (p=0.074). The basic clinical characteristic of the baby blues seems to be due to an increase in the emotional reaction with a sharp feelings, leading to a lability rather than an affect sad tonality. The baby blues seems to be a physiological process whereby the intensity is influenced by psychological factors. Consequently the diminution of self-esteem with motherhood and the increase of stress in relation to the care of the baby appeared to be significant factors in the intensity of the baby blues. Moreover, the clinical characteristics found in this study implies that the baby blues is more related to hypomania rather than to depression syndrome. This non-pathological state could be the first stage leading to a puerperal psychosis in predisposed women, which is mainly characterized by manic symptoms.