Fetal membrane at the feto-maternal interface: An underappreciated and understudied intrauterine tissue.

While most intrauterine tissues are thoroughly studied for their role in pregnancy maintenance and their contribution to labor initiation, the fetal membranes (i.e., amniochorionic membranes) are primarily overlooked.[1,2] The fetal membrane lines the intrauterine cavity (Figure 1A) and provides critical mechanical, immune, and endocrine support to protect the fetus during gestation[1,3–12] and has been shown to provide vital labor initiating signaling at term and preterm.[2,5,13–20] The function of the fetal membrane is derived from its unique makeup of multiple collagen layers,[21–23] along with fetal-derived cells that line with maternal decidua, forming the feto-maternal interface. A summary of the structure and function of the fetal membranes and the challenges researchers face studying this tissue are described below.