Amniochorionmembran

Amniochorionmembran, commonly referred to as the amniochorionic membrane, is the fetal membrane formed by the fusion of the amnion and chorion surrounding the developing embryo and fetus. The fusion creates a single, continuous membrane that encloses the amniotic cavity and contributes to the fetal membranes supporting pregnancy.

Formation and structure: The amnion arises from the inner cell mass (epiblast), while the chorion develops from extraembryonic mesoderm and trophoblast. As gestation progresses, these two membranes fuse to form the amniochorionic membrane. The fused membrane lines the inside of the chorionic sac and, together with placental structures, constitutes part of the fetal–maternal interface.

Function: The amniochorionmembran provides mechanical protection for the fetus and helps maintain the intrauterine environment by containing the amniotic fluid. It contributes to the barrier and support functions associated with the fetal membranes and participates in the development of the placenta.

Clinical significance: Disruption or premature rupture of the amniochorionmembran can lead to premature rupture of membranes (PROM), preterm birth, and an increased risk of infection. Abnormal persistence or separation of the membranes during development can complicate pregnancy. In medical procedures such as amniocentesis and fetal surgeries, membrane integrity is clinically important.

See also: Amnion; Chorion; Placenta; Fetal membranes; Amniotic fluid.