Amniotic fluid consists mostly of water with small amounts of organic and inorganic substances such as albumin, urea, creatine, phospholipids, fructose, fat, leukocytes, epithelial cells, enzymes and hair. The composition of amniotic fluid changes over the course of the pregnancy. In early pregnancy, amniotic fluid has a composition similar to maternal plasma and in later pregnancy the amniotic fluid becomes hypotonic due to the presence of fetal urine.
The amniotic fluid serves a number of functions for the developing embryo/fetus. The amniotic fluid:
- surrounds the developing fetus
- helps to maintain a constant body temperature and
- cushions the fetus from trauma by blunting and dispersing outside forces
In addition, the fluid-filled cavity provides an environment that allows free movement for muscular development. The fluid also keeps the embryo from becoming entangled with the membranes and facilitates symmetrical growth of the fetus.