3. IntroductionPrelabour rupture of the membranes (PROM) is defined as spontaneous rupture of the membranes before the onset of regular uterine contractions. It occurs in 6-19% pregnancies at term. Around 60% of women will labour within 24 hours and 90% within 48 hours. A remarkably consistent 2-5% remains undelivered within 72 hours. It is possible that this last group may have a biochemical imbalance that is responsible not only for their inability to go into labour, but also for the frequently observed poor progress when labour is induced.