Smartphones have become an integral part of our everyday lives. During pregnancy, they often serve as an important tool for accessing information and entertainment and for keeping in touch with others. However, with the birth of a child many things change in the lives of parents. There is still little research into whether and to what extent parents' smartphone use has an impact on their relationship with their child. The study investigated how parents use their smartphones before and after the birth of the first child and if parental smartphone use influences the sensitivity of parents and thus the interaction and attachment relationship between parents and their infants. A large proportion of the population uses a smartphone. Thus, the specific influence of smartphone use could not be determined. Therefore, this project aimed to assess the possible relationship between the duration and type of smartphone use and parents' sensitivity toward their child. There were three assessment times: the first time in the last trimester of pregnancy, then six to eight weeks after birth and a final time when the child was 3 to 4 months old. By including usage behavior in the last trimester of pregnancy, we intended to better understand possible changes around the birth. We used questionnaires for all parents and conducted interviews with a subsample of mothers. In addition, a short play sequence between the three-month-old child and his or her mother or father was video recorded.Until now, expectant parents have been largely left to their own devices wondering whether the use of digital media could affect their relationships with their children. In order to provide parents with evidence-based advice on the use of smartphones in relation to early parenthood, we need reliable knowledge about smartphone use behavior and its potential influence on the interaction between parents and their infants.