Globe and Mail Update
It's one of the most common medical procedures involving childbirth, but apparently it doesn't work. Using a long-handled hook, a doctor or midwife will puncture the amniotic membranes - the bag of water - surrounding the fetus in the hopes of hastening delivery.
The procedure, called amniotomy, is also known as "breaking the waters." Medical experts have long assumed the hormones released in the sudden gush of amniotic fluid can help trigger stronger labour contractions and quicken cervical dilation.
But British researchers examined the existing scientific evidence and concluded that amniotomy doesn't ease delivery - and could slightly increase the chances that the woman will need a cesarean section.
They looked at 14 separate studies involving almost 5,000 women in Britain, the United States and Canada.
"In a normally progressing labour where there are no concerns about the baby's wellbeing, there is little current evidence to justify breaking the woman's waters," researcher Rebecca Smyth of the University of Liverpool said in an e-mail.
Over all, "it doesn't shorten the first or second stage of labour, it doesn't affect the woman's satisfaction with her childbirth experience and doesn't result in the child being in better condition immediately after birth," according to the findings published in the Cochrane Library, the publication of an international organization that evaluates medical research.
Yet many medical centres perform amniotomy for routine deliveries. One Toronto hospital does it for 80 per cent of the births under its roof.
Ms. Smyth noted that the research team didn't examine complicated labours. So in certain high-risk cases, there may still be a need to break the membranes for fetal monitoring or assisting the labour. But in typical deliveries, "the membranes should be allowed to rupture naturally," she said.