Very rarely, when the waters break during pregnancy at the start of labour, the umbilical cord slips down into the birth canal (a prolapsed cord). This is a medical emergency, as the start of labour usually follows soon after the waters break, and the cord will be compressed as the baby moves down into the birth canal, cutting off its oxygen supply. This problem is more common with breech births, as the smaller bottom is more likely than the larger head to allow the cord to slip past it into the birth canal.
The only treatment for a prolapsed cord is a Caesarean section as soon as possible. In the meantime, the mother may be placed in a kneeling position, with her head down on the bed and her bottom in the air. Drugs may be given to stop labour as well.