For most women, the pattern of labor is predictable. In general, women first note the onset of contractions that are relatively mild and irregular. As labor progresses, the contractions become stronger and more regular and of increased duration. Spontaneous rupture of membranes generally follows the development of a regular contraction pattern as cervical dilation progresses. In approximately 10% of cases, however, spontaneous rupture of membranes occurs prior to the onset of labor. This is defined as premature rupture of membranes (PROM).