Supine Hypotensive Disorder
Pregnancy Exercise: Concerns about Supine Exercise after the First Trimester
Hypotension is the medical term for low blood pressure. Supine Hypotensive Disorder 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) to the point that it restricts blood flow back to the heart. When blood pressure falls low enough, a woman will immediately feel intensely dizzy.
To prevent Supine Hypertensive Disorder (SHD), the American College of Obstetricians and Gynecologists (ACOG) advises women not to exercise on their backs (supine) after their first trimesters.
It has been theorized that prolonged or repeated compression of the vena cave might also reduce blood flow to the placenta, which could negatively impact fetal development.
Pregnancy Exercise: Why Many Perinatal Exercise Experts Consider Supine Exercise Risks Negligible
- Researchers have documented that true SHD 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 SHD 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 SHD 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 greater risks for pregnant women than Supine Hypotensive Disorder. 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.