Within the discourse of motherhood, medical expertise often played a dominant role, possessing the power to construct the image of ideal motherhood. However, the rise of social media altered the way people receive information and complicated the relations between expert opinions and actual mothering practice. This paper employs text analysis to examine the “co-empowermental knowledge” shared by the users of two online mothering forums. The major findings are as follows: first, in terms of audience studies, the mothers in the forums are practicing collective consciousness awakening and mutual empowerment by using knowledge they have co-constructed on social media. Second, along with the evolution of media, the sources of knowledge of the mothers and their subjectivity have shifted again and again, from oral tradition to media-based knowledge. This shift also illustrated the evolutionary path of informal support systems for mothers in Taiwan. Third, in terms of professional-user relationship, women in the new era enjoy more freedom to apply knowledge, to participate in consumption, and to pursue self-realization. At the same time, they also need help from the experts of the new era. The co-empowermental knowledge will begin a new wave of professional-user negotiation.