Glossary

Term · Pregnancy: Your Body

vasovagal syncope

Also: fainting, vasovagal faint, reflex syncope

Fainting caused by a reflex that briefly slows the heart and drops blood pressure. Often set off by heat, standing too long, dehydration, or pain.

In plain words

Vasovagal syncope is the medical name for a common kind of fainting. A reflex briefly slows the heart and widens blood vessels, so less blood reaches the brain. It can feel like graying out, , nausea, or a rush of heat before the faint. Pregnancy makes it more likely, because blood vessels are more relaxed and blood volume shifts. Heat, long standing, dehydration, and sudden pain can set it off. Most of the time it is harmless and brief. Fainting with chest pain, shortness of breath, a racing heart, or a head injury needs emergency care, so call 911 or go in now.

The deeper version

Vasovagal (reflex) syncope is mediated by a cardioinhibitory and vasodepressor response to triggers acting through the autonomic nervous system, with a prodrome of pallor, diaphoresis, and nausea. In pregnancy, vasodilation from progesterone, the of late gestation, and reduced effective circulating volume increase susceptibility. The ESC syncope guideline (Brignole et al., 2018) and the HRS expert consensus statement (Sheldon et al., 2015) classify reflex syncope as the most common cause of transient loss of consciousness and recommend that other causes, especially cardiac arrhythmia and structural heart disease, be excluded when features suggest them. Clinical data on fainting specifically in pregnancy are limited. The main controversy concerns which patients need extended monitoring, and syncope in late pregnancy is evaluated carefully because of possible hemorrhage or cardiac causes.

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Sources

  • European Society of Cardiology — 2018 ESC Guidelines for the diagnosis and management of syncope. European Heart Journal 2018
  • Sheldon RS et al. for the Heart Rhythm Society — 2015 Heart Rhythm Society expert consensus statement on the diagnosis and treatment of postural tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope. Heart Rhythm 2015
  • American College of Obstetricians and Gynecologists — Physical Activity and Exercise During Pregnancy and the Postpartum Period, Committee Opinion 804, 2020

The Mothership Topic Wiki is general information for mothers and the people who care for them. It is not medical, legal, or mental-health advice and does not create a provider relationship. Experiences posted by members are their own. In an emergency call 911. If you are having thoughts of harming yourself, call or text 988.