Sudden cardiac arrest (SCA) is a life-threatening electrical malfunction that causes the heart to stop beating effectively. An Automated External Defibrillator (AED) delivers a controlled electrical shock to reset the heart’s rhythm. Although cardiac arrest is rare during pregnancy, it is highly time-sensitive and requires immediate action. The presence of a fetus should never cause hesitation in starting resuscitation, including the use of an AED, as prompt intervention offers the best chance of survival for both the mother and the unborn child.
Maternal Survival is the Priority
The immediate and primary focus in any maternal cardiac arrest scenario is the successful resuscitation of the mother. The fetus cannot survive unless effective circulation is restored to the mother. Attempting to save the mother is therefore the fastest and most reliable way to save the fetus. The electrical current delivered by an AED is directed across the mother’s chest, and studies indicate that the energy transmitted to the fetus is minimal. Standard adult AED pads and energy levels should be used without modification, as the minimal theoretical risk is vastly outweighed by the certainty of death if the intervention is withheld.
Positioning for Effective Circulation
While heart compressions are delivered as they are for any adult, later pregnancy requires a specific positional modification. When a pregnant person lies flat, the enlarged uterus can severely compress major blood vessels (the inferior vena cava and the aorta). This compression, known as aortocaval compression, dramatically reduces the volume of blood returning to the heart and the effectiveness of chest compressions. To overcome this, the uterus must be manually displaced to the left side during all resuscitation efforts.
This manual Left Lateral Uterine Displacement (LUD) is performed by continuously pushing the uterus away from the midline toward the patient’s left. Alternatively, the person can be placed on a firm surface with a slight left lateral tilt of about 15 to 30 degrees, while ensuring chest compressions remain effective. Maintaining this displacement is crucial because it helps restore blood flow to the heart, improving the mother’s chances of achieving a return of spontaneous circulation (ROSC).
Adjusting AED Pad Placement
Applying the AED pads correctly ensures the electrical current passes directly through the heart muscle. The standard adult placement, known as anterolateral, involves placing one pad on the upper right chest and the other on the lower left side below the breast. Enlarged abdomen or breast tissue may sometimes interfere with pad adherence.
If anterolateral placement is not feasible, an alternative method called anterior-posterior (AP) placement may be used. This technique involves placing one pad on the front of the chest, over the lower sternum, and the other pad on the patient’s back, between the shoulder blades. This configuration ensures the electrical current effectively traverses the heart from front to back, and establishing clear, firm skin contact is the primary consideration for delivering the therapeutic shock.
Fetal and Delivery Considerations
Once the initial resuscitation phase is complete, the situation transitions into a phase requiring advanced medical care. If a successful return of spontaneous circulation (ROSC) is achieved, the mother requires immediate transport to a hospital for ongoing monitoring and management. Medical teams will then focus on monitoring the fetal heart rate and assessing viability to determine the safest next steps for the pregnancy.
If initial resuscitation efforts fail, medical professionals may consider a time-sensitive emergency procedure known as Perimortem Cesarean Section (P-CS). The goal of P-CS is primarily to improve the mother’s chances of survival by rapidly relieving the aortocaval compression caused by the pregnant uterus. Current guidelines suggest P-CS should be initiated if ROSC is not achieved within four minutes of cardiac arrest, aiming to deliver the fetus within the fifth minute. This rapid delivery can improve the mother’s cardiac output by approximately 25%.