While a fetus is growing inside a mother’s womb it is protected by a lining or membrane inside the uterus known as the amniotic sac. http://www.health.com/health/library/mdp/0,,sta123161,00.htmlThe amniotic sac contains the fetus and fluid called the amniotic fluid. This is a clear to yellowish fluid liquid that surrounds the fetus. http://www.pregnancytoday.com/glossary/12-Amniotic+Sac/ The purpose of the amniotic sac is protecting the fetus from any external contact with the outside world such as when the mother falls, bumps into anything or any knocks to the mother’s belly. http://www.americanpregnancy.org/duringpregnancy/fetallifesupportsystem.html

The amniotic sac, which develops early in a woman’s pregnancy, consists of two parts. The outer layer of the thin membrane is called the chorion. The chorion surrounds the embryo, which later becomes the fetus. The second part of the amniotic sac, the amnion, is the inner layer. The amnion typically grows approximately 10 to 12 days after the amniotic sac develops. http://www.merckmanuals.com/home/sec22/ch257/ch257c.html#MMHE_22_257_02

As the pregnancy progresses, the fetus grows living within the amniotic sac. Typically, when the labor and delivery process starts, an expectant mother may experience what’s known as her water breaking. When this occurs, the amniotic sac ruptures indicating the start of labor.

There are potential problems with an amniotic sac, such as too much or too little amniotic fluid that can cause concerns for healthcare professionals. Typically, when the amniotic sac ruptures, for instance, the labor and delivery process is starting. However, it can rupture prematurely. When it does and labor doesn’t start within 24 to 48 hours, there is an increased risk of infection to the fetus and uterus. http://www.merckmanuals.com/home/sec22/ch261/ch261b.html?qt=amniotic sac&alt=sh#sec22-ch261-ch261b-1265b

There are some rare medical conditions caused by the amniotic sac. The amniotic band syndrome, or constriction ring syndrome, is the fibrous bands of the amniotic sac that entangles around the fetus as it develops. The syndrome causes deformities in limbs, toes and fingers because the band wraps around them. http://www.childrenshospital.org/az/Site1156/mainpageS1156P0.html