Les membranes fœtales : développement embryologique, structure et physiopathologie de la rupture prématurée avant terme

Fetal membranes development is a complex process. The amniotic and exocoelomic cavities are appearing first. The rapid growth of the amniotic cavity is leading to the disappearance of the exocoelomic cavity and the chorion is merging with the decidua. Fetal membranes consist of three layers: the amnios and the chorion, issued from fetal tissues and the decidua issued from maternal tissue. A balance between the synthesis and the degradation of membranes components is physiologic throughout the gestation. Two main mechanisms are involved in the degradation process: apoptosis in the cellular compartment and matrix metalloproteinase (MMP) in the extracellular matrix. Regulation of MMP is depending on factors increasing their expression (cytokines) and factors decreasing their activity tissue inhibitor of metalloproteinases (TIMPS). Particular conditions can induce an unbalance between synthesis and degradation leading to the weakening of the membranes. Different factors can be associated to induce this unbalance: infection, hormonal factors, default in membranes fusion, oxidative stress and mechanic factors. In fine, the spontaneous rupture of the membranes is always occurring in regard of the uterine cervix after a process started several weeks before.