Final answer:
The term used to describe the structure that breaks prior to delivery and signals the onset of labor is A) Bag of Waters, also known as the amniotic sac.
Step-by-step explanation:
The term commonly used to describe the structure that breaks prior to delivery and often signals the onset of labor is A) Bag of Waters, which is another way to refer to the amniotic sac. The amniotic sac is a fluid-filled membrane that encloses the fetus within the uterus. This event, also known as the 'breaking water,' typically signifies that labor is about to begin or has started.
During childbirth, the breaking of the amniotic sac or 'water breaking', indicates the release of the forewaters, allowing labor to progress. The rupture can occur spontaneously at term, known as 'spontaneous rupture of membranes' (SROM), or before labor at term, referred to as 'premature rupture of membranes' (PROM). In most cases, labor will begin within a day, and the process of childbirth will continue through stages such as dilation of the cervix, birth, and afterbirth.