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safely and efficiently manage prolapse of the umbilical cord to improve perinatal outcome whilst minimising maternal risk.
Introduction
Definition and incidence
Cord prolapse occurs when a loop of umbilical cord descends below the presenting part and the membranes are ruptured. Umbilical cord prolapse occurs in approximately 0.2% of all births.
A high percentage of mothers are multiparous. The incidence of prolapsed cord was 0.6% of all births in 1932. The reduction in frequency of the complication probably reflects reduction in family size, as well as changes in obstetric practice. These include the increased use of elective and intrapartum CS for a noncephalic, or an unengaged, presenting part and a more active approach to intrapartum management of the very preterm fetus.
Significance
In cord prolapse, the fetal perinatal mortality has been as high as 25–50% from asphyxia due to:
mechanical compression of the cord between the presenting part and bony pelvis
spasm of the cord vessels when exposed to cold or manipulations.
The perinatal mortality rate associated with umbilical cord prolapse has also fallen. One recent large study found a perinatal mortality rate of 91/1000. The cause of death for infants born after umbilical cord prolapse now seems to be related more to the complications of prematurity, associated congenital malformations and low birthweight, than to intrapartum asphyxia as such.
It is considered that part of the fall in perinatal mortality is due to the more rapid and frequent use of CS, once a prolapsed cord has been diagnosed. However, given the association between umbilical cord prolapse and preterm birth, improvements in neonatal intensive care are probably at least as important.
Clinical management
Aetiology
Umbilical cord prolapse tends to occur when the presenting part does not snugly fit in the lower pelvis and this, in turn, could be due to fetal causes such as:
Or maternal causes such as:
contracted pelvis
pelvic tumours
multiparous women with an unstable lie
low-grade placenta praevia
long cord
sudden rupture of membranes in polyhydramnios.
Other risk factors
In one series, obstetric interventions (such as amniotomy, scalp electrode application, intrauterine pressure catheter insertion, attempted external cephalic version and expectant management of premature rupture of membranes) preceded 47% of umbilical cord prolapse.
Diagnosis
Clinical suspicion
A high presenting part can raise suspicions of a problem with cord presentation or prolapse especially if the fetal heart rate is showing early decelerations suggestive of cord compression.
Vaginal examination
This should be performed carefully and thoroughly to check if cord is palpable. If membranes are intact and the cord is felt this is termed cord presentation, but if the membranes are ruptured, the term is cord prolapse. The next consideration is to ascertain whether the cord is pulsating; i.e. whether the fetus is alive or dead – this must be performed gently, with minimum pressure on the cord, to avoid further compression or even spasm.
Ultrasound
An ultrasound scan can be performed to confirm a fetal heartbeat, if this facility is rapidly available. Fetal heart monitoring should be started/continued with whatever tools are to hand (Pinard/Doppler/cardiotocography). Colour flow Doppler can be useful if there is reason to suspect cord presentation.
Obstetric management of umbilical cord prolapse
Obstetric management of umbilical cord prolapse has largely been unchanged since the 1950s. The approach if the baby is alive and of a viable gestation continues to be elevation of the presenting part and rapid delivery, usually by CS (unless the cervix is fully dilated and vaginal delivery can be expedited quickly). Any oxytocin infusion should be turned off.
Early diagnosis is important and continuous electronic fetal monitoring may be of assistance as fetal heart rate changes frequently recur: the speed required to expedite delivery will vary according to whether there is a bradycardia that does not respond to the measures mentioned below, or whether the fetal heart remains normal. In either situation, if the cervix is fully dilated and the presenting part well down in the pelvis, rapid vaginal delivery can be effected.
A management plan is shown in Algorithm 32.1.
Measures that can be employed to reduce cord compression and improve the fetal heart rate
A number of manoeuvres are described to reduce the cord compression, including manual elevation of the presenting part of the cord, tocolysis, bladder filling, placing the patient in the knee–chest position and funic reduction.
Traditionally, management of umbilical cord prolapse has included knee–chest or Trendelenburg positioning and manual elevation of the presenting part of the fetus above the pelvic inlet, to relieve cord compression. Provided that delivery is not imminent and the fetus is viable, this traditional management occurs while preparations for emergency CS are made.
Measures to perform intrauterine fetal resuscitation are indicated if there is concern about the fetal heart rate: increasing the intravenous fluid rate, administering oxygen by facemask and discontinuing the oxytocin infusion are indicated. If the umbilical cord visibly protrudes through the introitus, it should be replaced in the vagina with the minimum of handling. If this is not possible it can be laid carefully between sterile gauze soaked in warm, physiological saline.
If the cord is nonpulsatile or the fetal heart is not audible the importance of prompt ultrasound assessment is vital and urgent as it has been demonstrated that fetal heart movements can be visualised in such circumstances and fetal resuscitation, as described above, should be carried out urgently.
An advance in the management of umbilical cord prolapse has been the development of bladder filling (unless rapid vaginal delivery is planned). Bladder filling was first proposed by Vago, in 1970, as a method of relieving pressure on the umbilical cord. Bladder distension raises the presenting part of the fetus off the compressed cord for an extended period of time, thereby eliminating the need for an examiner’s fingers to displace the presenting part. A number 16 Foley catheter is placed into the urinary bladder. The bladder is filled, via the catheter, with physiological saline by a standard infusion set. The quantity of saline needed is determined by the fetal heart rate response and the appearance of the distended bladder above the pubis, with 500 ml usually being sufficient. The balloon is then inflated, the catheter is clamped and the drainage tubing and urine bag are attached and secured, ready for when the fluid is released prior to CS.
Bladder filling has an additional advantage in that the full bladder may decrease or inhibit uterine contractions. In a series by Chetty and Moodley, there were no cases of perinatal mortality.1 All the babies had Apgar scores of 6 or more and the mean elapsed time from diagnosis to delivery was 69 minutes. Eight women in their study delivered after an elapsed time of 80 minutes or more.
Tocolysis may be initiated to reduce contractions and improve bradycardia by using terbutaline 0.25 mg subcutaneously. If there is no evidence of fetal distress, it may be reasonable to proceed with a regional block (but conducted in left lateral, not sitting, position). The bladder is emptied by unclamping the catheter at the time of the skin preparation.
Vaginal delivery can be conducted when umbilical cord prolapse occurs at full dilatation with either the vacuum extractor or forceps, but only if the delivery is anticipated as being straightforward and easy: this is no time to embark on a complicated or protracted instrumentation that will exacerbate cord compression and potentially worsen the fetal condition.
The evidence relating to the interval between diagnosis and delivery being associated with stillbirth and neonatal death is conflicting. Neonatal condition, assessed by Apgar scores and paired cord blood gas analysis, is more likely to be influenced by the condition of the baby during the problem, rather than the time interval itself and fetal mortality has been more consistently attributed to prematurity and congenital anomalies. Birth asphyxia is, nevertheless, important and when this condition occurs outside of hospital (approximately 25% of patients) it carries a perinatal mortality rate as high as 86.4%.
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