If the high level of mental vulnerability marks the postpartum period, there are fewer mental diseases during pregnancy. Nevertheless, this period is marked by the importance of psychological change and the easier accessibility at psychotherapeutic interventions: then, unconscious conflicts can be approached as well as traumatic events. A lot of emotional and behavioral disorders remain within the norm. When the disorders are serious, they must be subjected to both therapeutic and preventive interventions to make sure the pregnancy goes as well as possible until birth and to help establish the mother-baby relationship. At the same time, these interventions are also a means of preventing postpartum disorders, in particularly postpartum depression. Specific disorders' such as denial of pregnancy (approximately 3 for 1,000) must be known, because there is a risk of infanticide. As for mental disorders already known, they involve cooperation between the maternity ward, physicians and the psychiatric department for the follow-up.