Cardiac Arrest in Pregnancy

There are differences between cardiac arrest and resuscitation in pregnancy compared with standard adult resuscitation. Always follow local and national guidelines, get formal training and involve experienced seniors when managing critically ill patients. The relevant RCOG guidelines on maternal collapse are from 2011. This overview is to help you understand the concepts in preparation for your exams.


Causes of Cardiac Arrest in Pregnancy

The Resuscitation Council UK list the reversible causes of adult cardiac arrest as the 4 Ts and 4 Hs:

4 Ts:

  • Thrombosis (i.e. PE or MI)
  • Tension pneumothorax
  • Toxins
  • Tamponade (cardiac)


4 Hs:

  • Hypoxia
  • Hypovolaemia 
  • Hypothermia 
  • Hyperkalaemiahypoglycaemia, and other metabolic abnormalities


The RCOG guideline advises adding to the list:

  • Eclampsia
  • Intracranial haemorrhage


The three major causes of cardiac arrest in pregnancy to remember are:

  • Obstetric haemorrhage
  • Pulmonary embolism
  • Sepsis leading to metabolic acidosis and septic shock


Obstetric haemorrhage is a major cause of severe hypovolaemia and cardiac arrest. Remember the causes of massive obstetric haemorrhage:

  • Ectopic pregnancy (early pregnancy)
  • Placental abruption (including concealed haemorrhage)
  • Placenta praevia
  • Placenta accreta
  • Uterine rupture


Aortocaval Compression

After 20 weeks gestation, the uterus is a significant size. When a pregnant woman lies on her back (supine), the mass of the uterus can compress the inferior vena cava and aorta. The compression on the vena cava is most significant, as it reduces the blood returning to the heart (venous return). This reduces the cardiac output, leading to hypotension. In some instances, this can be enough to lead to the loss of cardiac output and cardiac arrest.

The vena cava is slightly to the right side of the body. The solution to aortocaval compression is to place the woman in the left lateral position, lying on her left side, with the pregnant uterus positioned away from the inferior vena cava. This should relieve the compression on the inferior vena cava and improve venous return and cardiac output.


Resuscitation in Pregnancy

Several factors make resuscitation more complicated in pregnancy:

  • Aortocaval compression
  • Increased oxygen requirements
  • Splinting of the diaphragm by the pregnant abdomen
  • Difficulty with intubation
  • Increased risk of aspiration
  • Ongoing obstetric haemorrhage


Resuscitation in pregnancy follows the same principles as standard adult life support, except for:

  • 15 degree tilt to the left side for CPR, to relieve compression of the inferior vena cava and aorta
  • Early intubation to protect the airway
  • Early supplementary oxygen
  • Aggressive fluid resuscitation (caution in pre-eclampsia)
  • Delivery of the baby after 4 minutes, and within 5 minutes of starting CPR



Immediate caesarean section is performed in a pregnant woman when:

  • There is no response after 4 minutes to CPR performed correctly
  • CPR continues for more than 4 minutes in a woman more than 20 weeks gestation


The aim is to deliver the baby and placenta within 5 minutes of CPR commencing. The operation is performed at the site of the arrest, for example, in A&E resus or on the ward.

The primary reason for the immediate delivery is to improve the survival of the mother. Delivery improves the venous return to the heart, improves cardiac output and reduces oxygen consumption. It also helps with ventilation and chest compressions. Delivery increases the chances of the baby surviving, although this is secondary to the survival of the mother.


Last updated September 2020
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