Umbilical Cord Prolapse

Umbilical cord prolapse occurs after the membranes rupture, when the cord descends through the cervical os. In an overt prolapse, the cord lies below the presenting part and may be visible at the introitus. In an occult prolapse, it remains beside or above the presenting part and cannot necessarily be seen or felt. The danger is mechanical. The presenting fetus can press the cord against the cervix or maternal pelvis, especially during contractions. Venous flow is compromised first; more severe or sustained compression then reduces arterial flow. Fetal oxygen delivery falls, so the fetal heart rate may change abruptly and hypoxia can develop quickly. Cord presentation is different: the cord is positioned between the presenting part and the membranes while the membranes are still intact. It can become a prolapse when the membranes break, but it is not itself a prolapse.