An Automated External Defibrillator (AED) is necessary for a pregnant woman experiencing sudden cardiac arrest (SCA). SCA is a life-threatening electrical malfunction of the heart, and immediate defibrillation is the only definitive treatment for the most common cause, ventricular fibrillation. Hesitation to use the device, often driven by fear of harming the fetus, is detrimental, as any delay dramatically lowers the chance of survival for both the mother and the fetus. The American Heart Association advises that the benefits of immediate intervention significantly outweigh the minimal theoretical risks.
Medical Rationale for Immediate AED Use
Maternal survival is the single most important factor determining the fetus’s outcome during a cardiac arrest. A sudden cardiac arrest immediately stops the flow of oxygenated blood, causing both the mother and the fetus to experience rapid oxygen deprivation. The fetus is entirely dependent on the mother’s circulation for oxygen and nutrients, meaning fetal survival is impossible without maternal resuscitation.
SCA is fundamentally an electrical problem. An AED delivers a controlled electrical shock to the chest to interrupt this chaotic activity, allowing the heart’s natural pacemaker to reset a normal rhythm. The electrical current is primarily targeted at the heart muscle and does not travel through the lower abdomen, minimizing risk to the fetus.
For every minute that passes without defibrillation during a shockable rhythm, the chances of survival decrease by approximately 7 to 10 percent. The high mortality rate associated with untreated SCA necessitates that rescuers treat the mother exactly as they would any other adult victim. Delaying the shock significantly compromises the survival of both patients.
Modified Pad Placement for Pregnant Patients
While the need for an AED is the same, anatomical changes in pregnancy require slight adjustments to the placement of the electrode pads. The primary goal remains to ensure the electrical current passes directly through the heart to be effective. The standard anterior-lateral placement, with one pad on the upper right chest and the other on the lower left rib cage, is often still effective and should be attempted first.
The lower pad may need a slight shift due to the enlarged breasts or to ensure it does not overlap with the abdomen. If the standard placement is not feasible, an anterior-posterior configuration is recommended. This involves placing one pad on the left side of the chest over the heart and the second pad on the back, between the shoulder blades. This alternative placement is highly effective for ensuring the shock traverses the heart.
Use adult-sized electrode pads regardless of the patient’s size or stage of pregnancy. The AED delivers a fixed, high-energy dose required for adult defibrillation. Rescuers must ensure the pads are placed on bare skin, are firmly adhered, and do not touch each other to prevent short-circuiting the electrical current.
Addressing Aortocaval Compression During Resuscitation
A mandatory procedural modification in pregnant cardiac arrest is addressing aortocaval compression, which occurs when the uterus is at or above the navel (typically after 20 weeks of gestation). When a pregnant woman lies flat on her back, the weight of the enlarged uterus compresses the major blood vessels—the inferior vena cava and the aorta. This compression dramatically reduces the amount of blood returning to the heart, severely compromising cardiac output and the effectiveness of chest compressions and defibrillation.
To counteract this effect, continuous manual left uterine displacement (LUD) must be performed simultaneously with CPR and AED use. LUD involves a rescuer using one or two hands to push the pregnant abdomen to the patient’s left side. This action physically lifts the uterus off the major vessels, restoring blood flow back to the heart and maximizing the oxygen delivery to both the mother’s brain and the fetus.
The rescuer performing LUD must maintain this displacement throughout the entire resuscitation effort, including during the AED’s analysis and shock delivery. While some historical guidance suggested tilting the patient, the current consensus favors manual LUD while keeping the patient flat on a firm surface for the most effective chest compressions. Rescuers should not delay the initial defibrillation attempt to perform LUD, but once the AED pads are in place, LUD should be initiated immediately and maintained until medical professionals take over.