Umbilical Cord Prolapse

Etiology

Certain features of pregnancy increase the risk for the development of umbilical cord prolapse by preventing appropriate engagement of the presenting part with the pelvis. These include fetal malpresentation, multiple gestations, polyhydramnios, preterm rupture of membranes, intrauterine growth restriction, preterm delivery, and fetal and cord abnormalities.[1] Nearly half of the cases of umbilical cord prolapse can be attributable to iatrogenic causes.[2] Iatrogenic risk factors include amniotomy without an engaged fetal presenting part, attempted external cephalic version in the setting of ruptured membranes, amnioinfusion, placement of a fetal scalp electrode or intrauterine pressure catheter, or the use of a cervical ripening balloon.[1]

Epidemiology

Estimates of the incidence of umbilical cord prolapse range from 1.4 to 6.2 per 1000.[3] The majority of cases of umbilical cord prolapse occur in single gestation pregnancies; in twin gestations, the incidence increases in the second twin.[2] Most prolapses occur shortly after rupture of membranes; one study estimates that 57% occur within five minutes of membrane rupture while 67% occur within one hour of rupture.[2] The incidence of umbilical cord prolapse is on a downward trend, which is thought to be secondary to the widespread use of cesarean sections for many of the risk factors of cord prolapse, such as fetal malpresentation.[4][5] Decreasing rates of grand multiparity worldwide are also thought to contribute to the reduced incidence.[5]

History and Physical

The occurrence of fetal bradycardia in the setting of ruptured membranes should prompt immediate evaluation for potential cord prolapse. There are two forms of umbilical cord prolapse.[1] The first, overt prolapse, occurs when the cord exits the cervix before the fetal presenting part; the second, occult prolapse, occurs when the cord exits the cervix with the fetal presenting part.[1] In overt prolapse, the cord is palpable as a pulsating structure in the vaginal vault. In occult prolapse, the cord is not visible or palpable ahead of the fetal presenting part. In overt prolapse, the diagnosis is clinical and made by palpation of a pulsating structure in the vaginal vault or visibly protruding from the vaginal introitus; this is typically accompanied by fetal bradycardia or severe variable decelerations, though fetal heart rate changes only present in approximately two-thirds of cases.[2][6] In occult prolapse, only fetal heart rate abnormalities may appear, as the cord will not be palpable or visible on examination. The diagnosis should be a consideration in cases of unexplained fetal heart rate changes in the setting of recent membrane rupture or other maneuvers that increase the risk of prolapse (for example, placement of a fetal scalp electrode).[1]

Evaluation

Umbilical cord prolapse is a clinical diagnosis and should be considered in the case of fetal bradycardia or recurrent variable decelerations, especially if they occur immediately after rupture of membranes. The diagnosis is confirmed by palpation of a pulsatile mass in the vaginal vault. No radiographic or laboratory confirmation is available, and funic decompression should be attempted as soon as the diagnosis is suspected. Antenatal ultrasound for cord presentation has been demonstrated to be a poor predictor of umbilical cord prolapse.[7]

Treatment / Management

The definitive management of umbilical cord prolapse is expedient delivery; this is usually by cesarean section. In rare cases, vaginal delivery or operative vaginal delivery may be faster and, thus, preferable, but this should only occur under the presence and guidance of an experienced obstetrician.[1]

Until delivery is possible, the cornerstone of management of umbilical cord prolapse is funic decompression, relieving the pressure on the cord by elevation of the fetal presenting part. Studies suggest that the interval to funic decompression may be more important to outcomes than interval to delivery.[8] Decompression should be done manually by the medical provider through the placement of their finger or hand in the vaginal vault and gentle elevation of the presenting part off the umbilical cord. The provider should be conscientious not to place any additional pressure on the cord, as this can cause vasospasm and worsen outcomes.[9] Placement of the mother in a steep Trendelenburg or knee-chest position can also aid in cord decompression. In cases of a potentially prolonged interval to delivery (i.e., the need for transfer to a hospital with obstetric capabilities), saline infusion into the bladder may aid in funic decompression and remove the need for continuous manual elevation by the provider.[10][11] If fetal decelerations persist and delivery is not imminent, the administration of a tocolytic can be attempted to relieve pressure on the umbilical vessels and to improve placental perfusion, thereby improving blood flow to the fetus.[12][13] Reduction of the cord into the os, which was common before the widespread availability of cesarean sections, has been associated with increased fetal mortality and is not routinely recommended except in cases of an expected long interval to delivery where other maneuvers have failed.[1](B2)

If the cord is visibly protruding from the introitus, it should remain warm and moist because the ambient temperature is significantly colder than the temperature in the uterus and can result in vasospasm of the umbilical arteries, contributing to fetal hypoxia.[1] One method described as preventing this is the replacement of the cord into the vaginal vault followed by insertion of a moist tampon to keep it in place.[14]

In very rare cases of umbilical cord prolapse in peri-viable pregnancies, case studies demonstrate that conservative management may allow the continuation of the pregnancy until reaching a more desirable gestational age.[9][15] However, a frank discussion should take place with the patient regarding the experimental nature of this treatment and its potential risks. (B3)

Pre-viable gestational age, lethal fetal abnormalities, or fetal demise are not indications for expedient delivery, and instead, a dilation and evacuation or labor induction should be the therapeutic choice, dependent on gestational age or maternal preference.[5]

Differential Diagnosis

Potential causes of a palpable mass in the vaginal vault include fetal malpresentation.[1] Possible causes of severe, prolonged fetal bradycardia include maternal hypotension, uterine rupture, vasa previa, and abruptio placentae.[1]

Prognosis

The rate of fetal mortality in umbilical cord prolapse is estimated to be less than 10%.[9][2][4] This reduction is a drastic decrease from earlier estimates of mortality, which ranged from 32 to 47%, which researchers hypothesize is due to the increased availability of cesarean sections and advances in neonatal resuscitation.[1][9] Gestational age and location of prolapse (inside versus outside the hospital) are the two significant determinants of outcome in umbilical cord prolapse.[5] Cord prolapse that occurs outside the hospital carries an 18-fold increased risk of mortality.[6] Premature infants and those with low birth weights have an increased risk of perinatal complications and twice the mortality.[9] Death in these infants appears to be attributable to their underlying conditions and the preterm delivery necessitated by the prolapse rather than complications of the prolapse itself. 

Complications

Outcomes for umbilical cord prolapse have drastically improved in recent years.[4] Still, a diagnosis of umbilical cord prolapse carries a risk of fetal mortality. Though rare, surviving infants may develop complications secondary to asphyxia, including neonatal encephalopathy and cerebral palsy.[16][17][18]