In 2007 our local maternity unit was advising pregnant mothers who have reached term to come and have their membranes swept in an attempt to start labour with needing a formal induction. This matters to many mothers as they cannot attend the low risk unit and use the birthing pool if they have labour induced with prostaglandins and an intravenous infusion.
I recall one mother who was given conflicting advice by different midwives. The patient attended to have a sweep only to be told by a different midwife that that sweeping was either a waste of time and she would not countenance it. This sort of discrepancy is a good reason to look for evidence of benefit and this is now available in the form of a Cochrane review in Issue 3 (2007) of the Cochrane Database of systematic reviews.
The authors found that one induction of labour could be avoided for every eight women who had a sweep (NNT of 8), and that “Sweeping of the membranes, performed as a general policy in women at term, was associated with reduced duration of pregnancy and reduced frequency of pregnancy continuing beyond 41 weeks (RR 0.59, 95% CI 0.46 to 0.74) and 42 weeks (RR 0.28, 95% CI 0.15 to 0.50).”
Were there any adverse events? Yes but they were not too serious “There was no evidence of a difference in the risk of maternal or neonatal infection. Discomfort during vaginal examination and other adverse effects (bleeding, irregular contractions) were more frequently reported by women allocated to sweeping.”
These results were found in women who had a sweep compared to no treatment, but there was not enough data to draw conclusions on the comparative effect of sweeping and prostaglandins.
Next time I am asked about the pros and cons of having a sweep I will be able to give a more informed answer!