Background: The mechanisms of disparities in maternal and perinatal health between migrant and native women are multiple and remain poorly understood. Access to and quality of care are likely to participate in these mechanisms, and one hypothesis is the existence of implicit biases among caregivers through which ethno-racial belonging can influence medical decisions and consequently engender healthcare disparities. Their existence and their role in the generation of non-medically justified differential care have been documented in the United States apart from perinatal care, but remain largely unexplored in Europe. In this article, we present the study protocol and theoretical framework of a study that aims to test and quantify the existence of implicit bias toward African Sub-Saharan migrant women among caregivers working in the perinatal field, and to explore the association between implicit bias and differential care. Material and methods: This study is based on an online survey to which French obstetricians, midwives, and anesthetists were invited to take part. The potential existence of implicit biases toward African Sub-Saharan migrant will be quantified through a validated tool, the Implicit Association Test. Then we will assess how implicit biases are likely to influence clinical decisions and lead to differential care using clinical vignettes designed by an experts group. Discussion: Implicit bias and differential care are concept that are tricky to capture and interpret. This research program opens up in France a field of research on certain forms of health discriminations and sheds new light on the issue of social inequalities in perinatal health. Study registration: Registration in the Open Science Framework portal: https://osf.io/djva7/?view_only=c6012ace3fe94165a65b05c2dc6aff9e