هبوط الحبل السري

الخلفية

There are three varieties of cord prolapse:

• Overt cord prolapse - if the presenting part of the fetus does not fit the pelvis snugly after membrane rupture, there is a risk that the umbilical cord can slip past and present at the cervix or descend into the vagina. This is known as overt cord prolapse. It represents an acute obstetric emergency, as prolapse exposes the cord to intermittent compression compromising the fetal circulation. Depending on its duration and degree of compression, fetal hypoxia, brain damage and even death can occur. Exposure of the umbilical cord to air causes irritation and cooling, resulting in vasospasm of the cord vessels.

• Occult cord prolapse - where the umbilical cord lies alongside the presenting part.

• Cord presentation - where the cord can be felt to prolapse below the presenting part with or without membrane rupture. The cord may slip to one side of the head and disappear as the membranes rupture. When the cord can be felt to prolapse below the presenting part before membranes have ruptured, this is referred to as funic presentation.

علم الأوبئة

حدوث

Estimates of the incidence of umbilical cord prolapse range from 1.4 to 6.2 per 1,000.¹ The perinatal mortality rate from cord prolapse is 91 per 1,000.² Overt cord prolapse occurs in more than 1% of breech deliveries:

• 0.5% cephalic and frank breech presentations.

• 4-6% complete breech.

• 15-18% footling breech.³

Transverse lie is also associated with a higher risk of cord prolapse. The incidence of umbilical cord prolapse is on a downward trend, which is thought to be secondary to the widespread use of caesarean sections for many of the risk factors of cord prolapse and also because of decreasing rates of grand multiparity worldwide.¹

The incidence of occult prolapse is unknown but 50% of monitored labours show fetal heart rate changes suggesting umbilical cord compression. This is usually transitory and relieved by changing the mother's position.

عوامل الخطر²

• Prematurity.

• Fetal congenital abnormality.

• Second twin (particularly if abnormal cord insertion.⁴

• تعدد الولادات.

• Low birth weight (<2.5 kg).

• Breech.

• Oblique, transverse and unstable lie.

• Cephalopelvic disproportion.

• Pelvic tumours.

• Low-lying placenta.

• الاستسقاء السلوي.

• Macrosomia.

• High fetal station.

• Long umbilical cord.

• Obstetric interventions including:

  • Amniotomy with high presenting part.⁵

  • Vaginal manipulation of the fetus with ruptured membranes.

  • Insertion of intrauterine pressure catheter.

  • Attempted external cephalic or internal podalic version.

Induction of labour with prostaglandins is not associated with an increased risk of cord prolapse. A Cochrane review showed no difference in the risk of cord prolapse between women who had artificial rupture of the membranes to speed up labour and those who did not.⁶

عرض

• Abdominal examination: an ill-fitting or non-engaged presenting part should alert one to the possibility of cord prolapse.

• Vaginal examination (VE) during labour - the cord may be seen protruding from the introitus or be palpable within the vaginal canal. If it is pulsating, the fetus is alive.

• Prolonged fetal heart rate decelerations and fetal bradycardia.

التحقيقات⁷

Routine antenatal ultrasound is not adequately sensitive to detect cord presentation. Most suspected cord presentations do not develop into a cord prolapse at delivery. Loops of cord in front of the presenting part can be visualised using colour Doppler studies. This is not routinely done but can be used to examine women serially at high risk.

الإدارة⁸

Treat a prolapsed cord as an acute obstetric emergency. Management is in secondary care and the principles are as follows:

• Resuscitation and oxygen as needed.

• If the fetus is viable, place the mother in the knee-chest position (patient facing the bed, chest level to bed, knees tucked under chest, pelvis and buttocks elevated) or head-down tilt in the left lateral position and apply upward pressure against the presenting part to lift the fetus away from the prolapsed cord. This can be done manually (gloved hand/two fingers pushing upwards against the presenting part or once the presenting part is above the pelvic brim, using continuous suprapubic pressure in an upwards direction) or by filling the urinary bladder.

• Proceed to emergency caesarean section as soon as possible, using tocolytics as needed if natural labour has started. Only proceed with vaginal delivery if delivery is imminent, the cervix is fully dilated and there are no contra-indications.

• Ensure resuscitation is available for the baby post-delivery.

• If the fetus has died, deliver in the manner that is safest for the woman.

التكهن

The rate of fetal mortality in umbilical cord prolapse is estimated to be less than 10%.¹ Prolapse occurring out of hospital has an eighteen-fold risk of mortality.

The perinatal mortality rate (associated with cord prolapse) is 91/1,000. Prematurity and congenital abnormality are underlying factors in most cases. Even congenitally normal, full-term babies can die as a consequence of cord prolapse - home birth and delay in transfer to hospital have been identified as particular risks in these cases.²

The most common serious morbidities associated with cord prolapse relate to asphyxia: hypoxic brain injury and cerebral palsy.⁹ There are few long-term studies looking at long-term sequelae of cord prolapse.

الوقاية²

• Discuss admission with all pregnant women with transverse, oblique or unstable lie from 37 weeks of gestation. Cord prolapses occurring in hospital have better outcomes than those occurring within the community. Advise women who choose to stay in the community that they will require rapid assessment if they start labour or have a spontaneous rupture of membranes and should seek help as soon as possible.

• نساء مع premature rupture of membranes and a non-cephalic presentation should be advised to be admitted.

• Avoid ARM where possible - if ARM is performed with a mobile presenting part, ensure arrangements have been put in place for an immediate emergency section should a cord prolapse occur.

• Whenever a VE or other obstetric procedure is performed following rupture of membranes with a high presenting part, avoid any upward pressure on the presenting part.

• Treat high-risk patients with continuous fetal monitoring during delivery.