Amniotic fluid is also called liquor amnii. It is the nutrient-rich liquid within the amniotic sac. The fetus moves and floats in this sac; amniotic fluid not only nourishes the fetus but also protects it. Some of the amniotic fluid, which protects and cushions the fetus against physical injury, seeps through the placenta and through the wall of the sac (which is only two cell layers thick) from the uterus. But most of it comes from fetal blood by way of the baby’s lungs and kidneys. This sac is more like a circulating bath than a pool.mycontentbreak By the time the baby is developed, the sac holds approximately a quart of fluid, of which about a third is recycled hourly. In the latter part of pregnancy, the fetus swallows a good deal (approximately 16.5 ounces) of this clear, sterile liquid daily.