A complication during labour: umbilical cord prolapse

The umbilical cord connects the baby from their navel (belly button) to the placenta inside the uterus. An umbilical cord prolapse occurs when the umbilical cord slips in front of the baby after the waters break. The cord can then pass through the open cervix. This generally occurs during labour but can happen when the waters break before labour begins.
 

Cord prolapse is diagnosed on examination, by ultrasound, or if the umbilical cord is palpable in the vagina or visibly protruding. It is often accompanied by a severe and sudden deceleration of the foetal heart rate, but this is not always the case [1].
 

Fortunately, umbilical cord prolapse is rare. A population-based study was carried out comparing all deliveries complicated by cord prolapse with deliveries without this complication [2]. Umbilical cord prolapse complicated 0.4% of all deliveries included in the study (456 out of 121,227). 

When the umbilical cord is compressed, it can be squeezed by the baby or the uterus during a contraction. This can reduce the amount of blood flowing through the cord, decrease the heart rate and therefore the oxygen supply to the baby [3].

Obstetric risk factors

Various risk factors for cord prolapse have been identified. The study of more than 120,000 deliveries [6] showed that:

Abnormal presentation was associated with a 5 times higher risk

Polyhydramnios (excess amniotic fluid) and umbilical cord knot each carry a 3 times higher risk

2 times higher risk in the event of premature birth

Induction of labour doubles the risk

The absence of prenatal care carries a 1.4 times higher risk 

Male sex carries a 1.3 times higher risk. 

A low-birthweight baby (in particular under 2.5 kg) [7].

The risk is increased if the baby presents in a breech position [8].
 

Membrane rupture is also an important risk factor in umbilical cord prolapse. In most cases, it occurs shortly after membrane rupture. There is nearly a 9 times higher risk following membrane rupture [9]. One study found that 57% of cases occur within 5 minutes of rupture, and 67% within one hour of rupture. Only 5% of cases occur more than 24 hours after rupture [10]. 

Iatrogenic causes of umbilical cord prolapse 

Iatrogenic causes are defined as effects resulting from a medical procedure or drug treatment.
 

Interventions during labour that are generally considered benign and common in labour management have been identified as iatrogenic risk factors for umbilical cord prolapse. Approximately 47% of cord prolapse cases may be associated with obstetric practices [11].

Recognised iatrogenic factors tend to share one of two characteristics: they are linked to interventions that may cause the foetal presenting part to be displaced out of the pelvis, or occur at the time of membrane rupture. These interventions include [12]:

Artificial rupture of membranes (especially if the foetal presenting part is not engaged)

The attempt to rotate the foetal head

Amnioinfusion (infusion of fluid into the amniotic cavity [13])

External cephalic version in a patient whose membranes have ruptured (a procedure that involves manipulating the baby, who is presenting bottom-first, through the mother's abdominal wall in order to turn it head-down [14])

Insertion of an intrauterine pressure catheter or a foetal scalp electrode, or insertion of a cervical ripening balloon catheter. 

However, even though studies show that these interventions increase the risk of umbilical cord prolapse, they would not increase the associated morbidity and mortality [15]. Indeed, these interventions are almost always carried out exclusively in the labour and delivery unit, where continuous external foetal monitoring is in place and an emergency caesarean can be performed rapidly.

Cases of cord prolapse require delivery as quickly as possible.

Umbilical cord prolapse is a rare complication, occurring on average in 0.4% of births. The consequences can be serious, as it can reduce the amount of blood circulating through the cord, lowering the heart rate and therefore the supply of oxygen. 

At delivery, several techniques will be used to protect the baby, including repositioning you and elevating the part of the foetus that is presenting. It is more likely that you will give birth by caesarean section, although a vaginal birth is possible in some cases.