Supine Hypotensive Syndrome: Myths vs Facts
Supine Hypotensive Syndrome, or SHS, is perhaps the most misunderstood condition of pregnancy. You’ll read some really scary myths common myths such as your baby’s oxygen supply will be cut off if you lie down on your back.
Hypotension is the medical term for low blood pressure. Supine Hypotensive Syndrome refers to positional low blood pressure that may result when the weight of the uterus compresses the vena cava (the largest vein of the torso) which reduces blood flow back to the heart and lowers blood pressure. When blood pressure falls low enough, the result is acute onset dizziness.
To prevent Supine Hypertensive Syndrome (SHS), the American College of Obstetricians and Gynecologists (ACOG) advises women not to exercise on their backs (supine) after their first trimesters.
Though it has been theorized that prolonged or repeated compression of the vena cave might negatively impact fetal development, recent well-designed studies show that arterial blood to the placenta is not significantly reduced when either lying on the back or while exercising on the back.
Supine Exercise During Pregnancy: Know the Facts
- Researchers have documented that true SHS occurs in less than 10% of all pregnancies. Therefore, 90% of women can safely exercise on their backs throughout their pregnancies.
- Women who experience these symptoms always feel an urgent need to either roll over or sit up, which quickly relieves symptoms.
- No documentation yet exists to support the premise that exercising on the back could negatively impact fetal development.
- No evidence exists that resting or sleeping on the back restricts blood flow.
- Rhythmic movement of the limbs, particularly the legs, acts like a pump, which actually increases the rate of blood flow return to the heart while exercising on the back. Additionally, gravity enhances the blood flow rate during exercises that incorporate raised legs.
Unfortunately, miscomprehension about SHS has led some women to unnecessarily fear that they might harm their babies while sleeping on their backs. However both mom and baby can rest easy. Sleeping on the back has never been shown restrict blood flow to the Placenta and baby.
Pregnancy Exercise: Precautions You Should Observe with Supine Exercise during Pregnancy
Still, because controversy about SHS persists, during pregnancy you should be cautious if you choose to exercise while lying on your back.
- Exercise on the back for short durations only.
- Watch out for feelings of dizziness.
- If you experience dizziness, do not exercise on your back.
Pregnancy Exercise: Avoid Prolonged Periods of Standing
Positional low blood pressure during periods of prolonged standing poses far greater risks for pregnant women than Supine Hypotensive Syndrome. Pregnancy hormones relax blood vessels, and because muscular contractions are responsible for pumping blood back to the heart, prolonged periods of standing and inactivity increases the likelihood of pooling of blood in the legs. Prolonged standing, especially by the third trimester, can dramatically reduce blood flow back to the heart, causing dizziness, fainting, and injury due to falls.