Just another small piece of evidence in how American birthing practices have gotten off track: A recent review of studies found the practice of "breaking the water," that is, rupturing the amniotic sac, had no effect on the onset or second stage of labor, the health of the baby, nor on the mother's satisfaction with the birth process.
Doctors in hospitals routinely rupture the sac, in the belief that this releases hormones that stimulate contractions. According to this article in Health Behavior News Service, this practice began in 1756, fer cripes sake.
So, when physicians reviewed 14 studies examining the effects of amniotomy, they found it seemed to be more folklore than good medicine.
This conclusion is echoed in the article, in which a university MD is willing to go on the record as saying that he doesn't care what the science says:
However, several American doctors said the findings are unlikely to change the way obstetricians help women give birth in the United States. “Most of us believe it works, so there will be a lot skepticism about this,” said Mark Nichols, M.D., professor of obstetrics and gynecology at Oregon Health & Sciences University.