Cord prolapse occurs when the umbilical cord prolapses through the birth canal, either preceding or simultaneously with the presenting part, and often before the cervix is fully dilated. It is generally more common when the fetus does not fully occlude the pelvic inlet and is frequently associated with obstetric interventions, such as artificial rupture of the membranes with a high presenting part, or manoeuvres to correct fetal malposition or presentation. The incidence of cord prolapse is around 0.1-0.6%, but exceeds 1% with breech presentations. Other risk factors include polyhydramnios, multiple pregnancy, preterm labour and cord abnormalities.
Problems and special considerations
Overt prolapse occurs when the cord advances beyond the presenting part and is palpable or visible in the vagina, while occult prolapse is when the cord descends alongside the presenting part but is neither visible nor palpable in the vagina. Almost invariably, the result is compression of the cord by the presenting part of the fetus, which effectively cuts off its own blood supply, making it a true obstetric emergency with a fetal mortality rate of up to 10%. Delivery must be achieved very rapidly to prevent hypoxic-ischaemic damage to the fetus, ideally within a few minutes of prolapse.
By definition, there is usually little, if any, warning of a cord prolapse. It usually occurs during procedures such as assessment of progress or artificial rupture of membranes, when it is detected by the appearance of the cord through the introitus or the palpation of a pulsatile vaginal mass, but it may present spontaneously as acute, severe fetal distress or the mother noticing ‘something coming down’. When there is high suspicion that artificial rupture of membranes may result in a prolapsed cord, a ‘controlled’ rupture of membranes is often done in the operating theatre.
Management options
The successful management of cord prolapse requires immediate delivery by caesarean section, although vaginal spontaneous or assisted delivery may occasionally be performed when delivery is imminent and cardiotocography is reassuring. Local guidelines should be developed, and a well-established mechanism for handling emergencies of this nature should be in place. Regular simulated drills will highlight weak points in the process and ensure that all staff are familiar with their roles. Well-recognised areas of delay include transfer of the patient to the operating theatre, gathering the theatre team, and waiting for inappropriate investigations or cross-matched blood.
The other danger of the need for rapid delivery is that important preparations may be overlooked in the rush: for example anaesthetic assessment, antacid premedication and removal of dentures. Damage to the bladder may occur if it is not emptied preoperatively.
However rapidly delivery can be achieved, every effort should be made to relieve the occlusion of the umbilical cord by manually lifting the presenting part off the cord. This can be difficult, but may be helped by maintaining a steep head-down tilt until delivery is imminent. Rapid transfer of the patient in this position, especially with a midwife supporting the fetus with her hand inside the birth canal, can be very fraught indeed. Instillation of saline into the bladder via a catheter may assist this manoeuvre, and tocolytics may be administered in the presence of fetal bradycardia or non-resolving abnormalities of the fetal heart trace.
General anaesthesia
Caesarean section in these circumstances is often best managed by induction of general anaesthesia. It is a fast and reliable technique, and the manoeuvres needed to relieve the pressure on the cord often preclude positioning the patient for a de novo regional block. If general anaesthesia is to be used, a preoperative airway assessment is mandatory. If a problem with intubation is anticipated, the anaesthetist may have to make the difficult decision - in conjunction with the obstetrician - of whether an attempt at regional anaesthesia is appropriate. It is impossible to give general guidance for individual cases of this nature, but the main precept is that the mother’s life should take priority over the fetus’s.
Steps should always be taken to protect against aspiration of gastric contents (see Chapter 59).
Regional anaesthesia
Cord prolapse does not necessarily rule out a regional block for caesarean section, especially if the mother already has a functioning epidural in situ. It is obviously better to avoid the risks of general anaesthesia in the unprepared patient if possible, and many mothers express a strong wish to be awake to witness the birth of their baby, if its viability is in doubt. The obvious problem with using an epidural block is the time delay while it takes effect, but various recipes for rapid top-up have been described (see Chapter 35, Epidural anaesthesia for caesarean section). Even if this is not fully effective by the time the operation starts, the first 2-3 minutes of surgery before the peritoneum is manipulated can be managed with a relatively low block. It is important in these circumstances for the anaesthetist to reassure the mother constantly (and often the partner as well). Good, sympathetic communication may mean the difference between failure and success.
Spinal anaesthesia is not recommended for the inexperienced, but a ‘rapid-sequence’ technique has been reported in such cases and may be attempted in the presence of a reassuring fetal heart trace. A strict time limit, however, should be applied and the clock watched by an independent observer. If a 3-minute cut-off point is used, and the mother is preoxygenated during the spinal attempt, then no time is lost if conversion to general anaesthesia is necessary. As with epidural anaesthesia, the mother may need support during the first few minutes before the block is fully established.
Key points
• The successful management of cord prolapse depends on good communication and well-rehearsed guidelines.
• General anaesthesia may be the best option, but the risks to the mother should be borne in mind.
• Regional anaesthesia is often possible, but should not be allowed to delay delivery.
Further reading
Holbrook BD, Phelan ST. Umbilical cord prolapse. Obstet Gynecol Clin North Am 2013; 40: 1-14.
Kinsella SM, Girgirah K, Scrutton MJ. Rapid sequence spinal anaesthesia for category-1 urgency caesarean section: a case series. Anaesthesia 2010; 65: 664-9.
Royal College of Obstetricians and Gynaecologists. Umbilical Cord Prolapse. Green-top Guideline 50. London: RCOG, 2014. www.rcog.org.uk/en/guidelines-research-services/guidelines/gtg50 (accessed December 2018).