Objective This study aimed to describe how parents and physicians experienced the informed consent interview and to investigate the aspects of the relationship that influenced parents’ decision during the consent process for a randomised clinical trial in a tertiary neonatal intensive care unit (NICU). The secondary objective was to describe the perspectives of parents and physicians in the specific situation of prenatal informed consent. Setting Single centre study in NICU of the Centre Hospitalier Intercommunal de Créteil, France, using a convenience period from February to May 2016. Design Ancillary study to a randomised clinical trial: Prettineo. Records of interviews for consent. Population: parents and physicians. Mixed study including qualitative and quantitative interview data about participants’ recall and feelings about the consent process. Interviews were reviewed using thematic discourse analysis. Results Parents’ recall and understanding of the study’s main goal and design was good. Parents and physicians had a positive experience, and trust was one of the main reasons for parents to consent. Misunderstanding (bad comprehension) was the main reason for refusal. Before birth, three situations can compromise parents’ consent: the mother already consented to participate in other studies, the absence of the father during the interview and the feeling that the baby’s birth is not an imminent possibility. Conclusions Confronting parents and physicians’ perspectives in research can help us reach answers to sensitive issues such as content and timing of information. Each different types of study raises different ethical dilemmas for consent that might be discussed in a more individual way.