Effect of amniotomy on the duration of spontaneous labour

Intentional artificial rupture of amniotic membranes is the most commonly performed procedure in modern obstetrics(1). It was first introduced by Thomas Denman, an English Obstetrician, in 1756. Mean length of first  and second stage of labour was approximately 9 hours in nulli-parous women  without regional analgesia and that the 95 percentile upper limit was 18.5 hours.  The mean length of first and second stage of labour in multi- parous  women without regional analgesia was  6 hours  and that the 95 percentile upper limit was  13.5 hours.(2) The primary aim of amniotomy is to increase contractions and shorten the duration of labour.

 With amniotomy, the production and release of local prostaglandins and oxytocin increase resulting in stronger contractions and quicker cervical dilatation. In some centers, it is routinely performed in all women and in many centers it is used for treatment of prolonged labour(1). Amniotomy allows detection of meconium stained liquor. With the active management of labour protocol introduced by O’Driscoll in 1993, the use of amniotomy has been widely accepted as part of labour. It is thought that when the membranes are ruptured, the production and release of prostaglandins and oxytocin contribute towards shortening labour (3). Others argue that the protective water is important for cervical dilatation. However, there are number of potential but rare risks associated with amniotomy like cord prolapse, fetal heart rate abnormalities and sepsis. The Randomized Controlled Studies included in the Cochrane review (1) that compared outcomes in women who had amniotomy with outcomes in women who did not have amniotomy had variable inclusion criteria and hence have conflicting results. Thus, a need for a well-designed large study to look at the outcomes of this intervention has been identified as a research priority.

1. Amniotomy for shortening spontaneous labor, Cochrane database of systematic reviews 2013, issue 6. Art.No: CD006167. DOI: 10.1002/14651858. CD006167 .pub4.
2. Kilpatrick SJ, laros RK Jr: Characteristics of normal labour Obstet  Gynecol 74:85,1989
3. Busowski JD1, Parsons MT. Amniotomy to induce labor. Clin Obstet Gynecol. 1995 Jun;38(2):246-58.