Water break during pregnancy is formally called amniorrhea in medical science. When the fetus is in the wombit is enveloped by a thin tunica, which is called fetal membrane. The liquid in it is amniotic fluid, usually called as water.
When a pregnant woman is at parturient time, she will face uterine contractions, which press the amniotic fluid in the fetal membrane to the ostium of uterus, making it widening. During this procedure, the membrane is also expanding until it breaks to let the amniotic fluid flow out from the vagina. Normally, the amniorrhea occurs when the ostium of uterus fully opens. If a pregnant woman faces amniorrhea twelve hours before delivery, she is still not at the stage of labor. However, the amnia is already broken, and a lot of amniotic fluid flow out, which is called early amniorrhea. http://sexualhealth.e-healthsource.com/index.php?p=news1&id=536053
at 12:40 AM on Dec. 8, 2009