The aim of breaking the waters is to speed up and strengthen contractions, with the intention of shortening labor. The membranes are punctured using a long handled hook, and it is thought that hormones in the amniotic fluid that flows out will stimulate contractions. In some centres, it is performed as a routine part of care for all women in labor -- in others it is used only for women with a clinical need to have their waters broken.
Ms Smyth came to these conclusions after she and colleagues had identified 14 relevant studies that involved almost 5,000 women. The overall quality of the studies was variable, making it difficult for the group to give firm recommendations about the use of amniotomy. There is a need for further research in this area.
"Our evidence suggesting this lack of effect should be discussed with women in the antenatal period," says Smyth.