With DS1 my waters broke spontaneously which kickstarted an 8-hour labour (tho the first 5-odd hours of contractions were mild). With DS2 I asked for ARM about six hours after my labour started ... bub was ready to pop out and membranes were bulging. Bub was born about 45 mins after. FYI - I didn't feel the ARM, just incredible relief as fluid gushed everywhere - it's one of my main memories of DS2's birth LOL.