Membrane Sweeping at Initiation of Labor Induction
Membrane Sweeping at Initiation of Labor Induction
Abstract & Commentary
By John C. Hobbins, MD, Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert.
Dr. Hobbins reports no financial relationship to this field of study.
Synopsis: Membrane sweeping at initiation of labor induction increased the spontaneous vaginal delivery rate, reduced oxytocic drug use, shortened induction to delivery interval, and improved patient satisfaction.
Source: Tan PC, et al. Membrane sweeping at initiation of formal labor induction: a randomized controlled trial. Obstet Gynecol. 2006;107:569-577.
The March issue of obstetrics and gynecology contained an article which may have a rejuvenating effect on the sometimes controversial practice of membrane sweeping.
Tan et al randomized 264 women scheduled for induction to either have membrane swept (136) or to not have this done (128) prior to induction. If the cervix allowed the introduction of a finger, the membranes were swept once clockwise and once counter clockwise as high as possible. If the endocervix could not be entered then the cervical canal was swept. All patients were then immediately followed by induction by progesterone pessaries or amniotomy, in the latter case, if the cervix were dilated to equal or greater than 3 centimeters.
Among many end points the authors scored the patients' satisfaction with the labor process by a simple analogue system.
With sweeping, there was an impressive difference in spontaneous vaginal delivery (69 % vs 56%), shorter labors (14 vs 19 hours), need for oxytocin augmentation (46% vs 59%), and less time of oxytocin infusion (2.6 vs 4.3 hours).
Interestingly some of the above variables translated into less total pain during labor (out of a scale of 1-10, 4.0 vs 4.7). Those swept had more discomfort during (obviously) and after the sweep (4.7 vs 3.5). No statistical differences were noted in the neonatal outcomes.
Commentary
Sweeping has been shown to cause release of phospholipase A and prostaglandins for as much as 6 hours. These, in turn, are instrumental in the initiation of labor, and if there is such a thing as Ferguson's reflex, the sweep may cause an endogenous release of oxytocin.1-4
So—why not do this on everyone? First, this study required that the patients proceeded immediately to induction after the sweep. The common practice in the United States is to send the patients home after a sweep to await initiation of spontaneous labor. Second, the study did not address maternal or neonatal sepsis, and probably would have been underpowered to evaluate neonatal infection in any case.
I bring this up because the sweep will be guaranteed to drag bacteria up into the lower uterine segment, where they can initiate their own cascade of events leading not only to labor but the consequences of their presence.
A few years back we attempted to document the accent of bacteria into the cervix during labor to validate the "insuck theory." This required putting an ultrasound opaque medium into the vagina, after which we traced the material with vaginal ultrasound. One patient was a nurse midwife who was scheduled to have her membranes swept to initiate labor. We invited her to have this done at the end of the study period so that we could see what happened to the ultrasound medium. Surprisingly, it lit up the entire lower third of the uterine cavity—far higher than the sweeping finger could be advanced. This medium could easily have represented bacterial.
I rest my case.
References
- Mitchell MD, et al. Rapid increases in plasma prostaglandin concentration after vaginal examination and amniotomy. Br Med J. 1977;2:1183-1185.
- McColgin SW, et al. Parturitional factors associated with membrane stripping. Am J Obstet Gynecol. 1993;169:71-77.
- Boulvain M, et al. Membrane sweeping for induction of labour. Cochrane Database Syst Rev. 2005 Jan 25;(1):CD000451..
- Boulvain M, et al. Does sweeping of membranes reduce the need for formal induction of labor? A randomized control trial. Br J Obstet Gynaecol. 1998:105:34-40.
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