amnionholte

Amnionholte, or the amniotic cavity, is the fluid-filled space inside the amnion that surrounds the developing embryo and fetus during pregnancy. It contains amniotic fluid, a protective medium that cushions the fetus, permits free movement, and helps maintain temperature and fluid balance. The composition and volume of amniotic fluid change over gestation and have diagnostic value in prenatal care.

Embryology and anatomy: The amnion is a thin fetal membrane derived mainly from the embryonic epiblast. As development proceeds, the amnion enlarges to form a sac that encloses the embryo, lying inside the chorion. The amniotic cavity is the space within this sac and is continuous with the broader placental structures through the fetal membranes.

Amniotic fluid sources and functions: In early pregnancy, amniotic fluid largely reflects maternal plasma. From about the second trimester onward, fetal urine becomes the major contributor to the fluid volume. The amniotic cavity provides mechanical protection, enables fetal movement, supports lung development, and participates in thermoregulation and fluid-electrolyte balance.

Clinical relevance: Abnormal amniotic fluid volumes are associated with adverse outcomes. Oligohydramnios refers to low amniotic fluid, which can indicate placental insufficiency, fetal renal abnormalities, or ruptured membranes. Polyhydramnios denotes excess fluid and may occur with fetal swallowing impairment, multiple gestations, or maternal conditions such as diabetes. Ultrasound assessment of the amniotic cavity and fluid index is a common prenatal tool.