What are the causes of syncope in pregnancy?

From the Guidelines

Syncope in pregnancy is most commonly caused by vasovagal reactions, orthostatic hypotension, and other neurally-mediated reflex syncope, as defined by the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1. The causes of syncope in pregnancy can be broadly categorized into several groups, including:

• Neurally-mediated (reflex) syncope, such as vasovagal syncope, carotid sinus syncope, and situational syncope, as outlined in the 2004 European Heart Journal guidelines on management of syncope 1
• Orthostatic hypotension, which can be exacerbated by the physiological changes of pregnancy, including decreased blood pressure in the first and third trimesters
• Cardiac arrhythmias, which may be triggered by hormonal changes during pregnancy
• Structural cardiac or cardiopulmonary disease, although this is a rare cause of syncope in pregnancy Other potential causes of syncope in pregnancy include:
• Dehydration and hypovolemia, which can lead to decreased blood flow to the brain
• Anemia, which is common in pregnancy due to increased blood volume and iron demands
• Hypoglycemia and hyperventilation, which can trigger syncope in susceptible individuals According to the 2017 ACC/AHA/HRS guideline, the evaluation and management of syncope in pregnancy should focus on identifying and addressing underlying causes, as well as providing guidance on lifestyle modifications to prevent recurrent episodes 1. The management of syncope in pregnancy typically involves avoiding triggers, changing positions slowly, staying hydrated, and ensuring adequate nutrition, with further cardiac evaluation necessary for recurrent episodes 1.

From the Research

Causes of Syncope in Pregnancy

• The causes of syncope in pregnancy can be attributed to various factors, including:
  • Supine position: Pregnant women who lie in a supine position may develop syncopal symptoms due to aortocaval compression 2
  • Systemic vasodilation: Decreased cardiac output or systemic vasodilation can lead to cerebral hypoperfusion, resulting in syncope 3
  • Orthostatic hypotension: A drop in blood pressure upon standing can cause syncope 3, 4, 5
  • Reflex syncope: Also known as neurogenic syncope, this type of syncope can occur due to various stimuli, such as vasovagal reaction or carotid sinus hypersensitivity 3, 4, 5
  • Cardiac causes: Arrhythmias, structural cardiac diseases, or other cardiac conditions can lead to syncope 3, 4, 5

Classification of Syncope

• Syncope can be classified into three primary categories:
  • Cardiac syncope: Caused by cardiac conditions, such as arrhythmias or structural heart diseases 3, 4, 5
  • Reflex syncope: Caused by neurogenic factors, such as vasovagal reaction or carotid sinus hypersensitivity 3, 4, 5
  • Orthostatic syncope: Caused by a drop in blood pressure upon standing 3, 4, 5

Pathophysiology of Syncope

• Syncope is a symptom of transient loss of consciousness due to cerebral hypoperfusion, which can be caused by various circulatory disturbances, such as brady- or tachyarrhythmias, or reflex cardioinhibition-vasodepression-hypotension 6
• The pathophysiology of syncope involves complex interactions between vascular, humoral, and cardiac factors, which can lead to transient systemic hypotension and cerebral hypoperfusion 6