May 4, 2026

This month, we are focusing on the care of obstetric patients. While these calls are relatively uncommon in EMS, they are high-risk and time-sensitive encounters. A strong understanding of pregnancy physiology is essential to providing safe and effective prehospital care. 

Pregnancy causes significant physiologic changes that affect how patients present, how they compensate, and how quickly they can deteriorate.

The easiest way to think about this is through the lens of the ABCs of our primary survey. 

Airway:  

Hormonal changes lead to swelling and increased blood flow in the airway tissues, making them more edematous and prone to bleeding. This means that what might normally be a straightforward airway can quickly become challenging. Visualization may be more difficult, and even minor trauma can cause bleeding that obscures landmarks. Pregnant patients are also at an increased risk of aspiration due to delayed gastric emptying. If an airway intervention is needed, approach this procedure with extra preparation. Anticipate difficulty, have suction ready, and be prepared to use adjuncts or backup strategies early. 

Breathing:  

As the uterus enlarges, it pushes the diaphragm upward, which reduces the amount of oxygen the lungs can hold in reserve. At the same time, the body’s oxygen demand increases to support the fetus. Even though pregnant patients compensate by breathing slightly faster and deeper, they ultimately have less reserve. This is why they can desaturate much more quickly than other patients, especially during periods of apnea or respiratory compromise. This means we need to intervene early — apply oxygen sooner, monitor closely, and avoid delays if respiratory status begins to decline. 

Circulation:  

Pregnancy has a significant impact on a patient’s cardiovascular system. Blood volume and cardiac output both increase, allowing pregnant patients to compensate for blood loss better than non-pregnant patients. However, this also means that classic signs of shock — especially hypotension — may not appear until later. A pregnant patient can lose a substantial amount of blood before their blood pressure drops, and when they do decompensate, it can happen quickly. Because of this, it is important to recognize early signs of hypoperfusion, such as tachycardia, pallor, or altered mental status, and resuscitate early! 

Positioning is another key consideration. In later pregnancy, the uterus can compress the inferior vena cava when the patient is lying flat. This decreases blood return to the heart and can worsen hypotension, particularly in already unstable patients. Simply shifting the uterus off midline — either manually or by placing the patient in a left lateral tilt — can significantly improve circulation. This is a simple intervention that should be used routinely in patients beyond mid-pregnancy. 

Finally, pregnancy creates a hypercoagulable state. While this helps reduce bleeding during delivery, it also increases the risk of serious conditions like pulmonary embolism and stroke. This is important to keep in mind when evaluating pregnant patients with unexplained shortness of breath, chest pain, or neurologic symptoms. 

This Week’s Take-Home Message:  

Pregnant patients are not our “standard” patients. They may appear stable longer than expected and can deteriorate quickly once their compensatory mechanisms fail. Understanding these physiologic differences directly impacts how we assess and resuscitate these patients in the field. 

Thank you, 

Shauna Combs, DO