An Automated External Defibrillator (AED) is a portable device that delivers an electrical shock to the heart during Sudden Cardiac Arrest (SCA). SCA occurs when the heart’s electrical system malfunctions, causing it to stop beating effectively. This life-threatening event requires immediate intervention to restore a normal rhythm. If a pregnant woman experiences SCA, the AED must be used without hesitation. Standard adult AED protocols apply, and the need for rapid defibrillation outweighs all other considerations for both the mother and the fetus.
The Immediate Need for Defibrillation
The primary goal during maternal cardiac arrest is the survival of the mother, as the fetus cannot survive if the maternal circulation fails. Cardiac arrest is a rapidly fatal condition where blood flow to the brain and other organs ceases within seconds. The mother’s survival is directly linked to the fetus’s chance of survival.
Defibrillation is a time-sensitive intervention that delivers a controlled electrical current to reset the heart’s electrical activity. Every minute that passes without defibrillation decreases the chance of survival by approximately 10%. Delaying or withholding the shock due to concerns about the pregnancy significantly lowers the survival chances for both individuals.
The electrical discharge from the AED stops the chaotic electrical activity of the heart, such as ventricular fibrillation, allowing a normal rhythm to resume. This energy is a brief, high-energy pulse directed across the chest, not a continuous flow. Restoring the mother’s circulation immediately far outweighs any theoretical risk to the fetus.
Specific Positioning and Pad Placement
While the urgency of AED use is the same as for any adult, a visibly pregnant patient requires specific modifications to the resuscitation technique. The most significant modification addresses the pressure the enlarged uterus places on major blood vessels in the abdomen. When the mother lies flat on her back, the uterus can compress the inferior vena cava and aorta, a condition known as aortocaval compression.
This compression reduces the amount of blood returning to the heart, potentially decreasing cardiac output by 30% to 40%. To counteract this, manual left lateral uterine displacement (LLUD) should be performed by pushing the abdomen toward the patient’s left side. A slight left lateral tilt of 15 to 30 degrees can also be achieved by placing a wedge under the right hip, though chest compressions must remain effective on a firm surface. Maintaining this displacement during cardiopulmonary resuscitation (CPR) helps optimize blood flow to the heart and the placenta.
The standard adult AED pad placement is maintained: one pad on the upper right chest and the other on the lower left side, near the armpit or below the left breast. If the standard lower pad placement risks contacting the abdomen, the pad must be moved superiorly onto the chest wall. The goal is to maximize the electrical current’s path through the heart while avoiding contact with the uterus. The standard energy dose for defibrillation is used for pregnant patients, typically 120–200 Joules for a biphasic shock, without reduction.
Understanding Risk to the Fetus
The question of whether the electrical shock from an AED will harm the unborn baby is a common concern, but evidence indicates the risk is negligible. The electrical energy delivered during defibrillation follows the path of least resistance, which is directly across the mother’s heart. This current is highly localized and minimal electrical energy reaches the fetus.
Successful maternal resuscitation is the most important factor for a positive fetal outcome. If the mother’s heart is not restarted, the fetus will inevitably die due to a lack of oxygenated blood supply. The immediate threat to the fetus is the complete absence of maternal circulation, not the electrical current.
The American Heart Association and other resuscitation bodies strongly support the use of AEDs in pregnancy, confirming that the benefits dramatically outweigh any potential risk. Responders should use the AED without hesitation, as this action provides the fetus with its only chance of survival.