A prolapsed umbilical cord occurs in about 1 of 1,000 deliveries. When the umbilical cord prolapses, the fetus’s body may put pressure on the cord and thus cut off the fetus’s blood supply.
This uncommon complication may be obvious (overt) or not (occult).
Overt prolapse
The membranes have ruptured, and the umbilical cord protrudes into or out of the vagina before the baby emerges. Overt prolapse usually occurs when a baby emerges feet or buttocks first (breech presentation Breech presentation Position refers to whether the fetus is facing rearward (toward the woman’s back—that is, face down when the woman lies on her back) or forward (face up). It’s important to check the baby’s... read more ). But it can occur when the baby emerges head first, particularly if the membranes rupture prematurely or the fetus has not moved down into the woman’s pelvis. If the fetus has not moved down, the rush of fluid as the membranes rupture can carry the cord out ahead of the fetus.
If the cord prolapses, cesarean delivery Cesarean Delivery Cesarean delivery is surgical delivery of a baby by incision through a woman’s abdomen and uterus. In the United States, up to 30% of deliveries are cesarean. Doctors use a cesarean delivery... read more 
must be done immediately to prevent the blood supply to the fetus from being cut off. Until surgery begins, a nurse, midwife, or doctor holds the fetus’s body off the cord so that the blood supply through the prolapsed cord is not cut off.
Occult prolapse
The membranes are intact, and the cord is in front of or next to the fetus or trapped in front of the fetus’s shoulder.
Usually, occult prolapse can be identified by an abnormal pattern in the fetus’s heart rate. Changing the woman’s position usually corrects the problem. Occasionally, a cesarean delivery is necessary.
