QuestionI have read that sleeping on the back can impede blood flow to the fetus. If I happen to be sleeping on my back, will I feel discomfort if the blood flow is being blocked? Or can the health of the baby be compromised without me knowing it is happening? Thank you very much.
AnswerThe question of lying, sleeping, and exercising on the back has been studied and in all instances, arterial blood flow to the placenta is not significantly impacted.
It had been theorized that the vena cava, the largest vein in the body, might be compressed by the weight of the uterus in the supine position but this theory has been largely discarded by the medical and fitness communities.
Compression of the vena cava, (called Supine Hypotensive Disorder) is sometimes confused with positional low blood pressure during pregnancy. Because pregnancy causes vasodilation, pooling of blood in the legs is fairly common. This causes an immediate reduction of blood flow to the brain and women will feel suddenly faint. This can occur while standing, sitting, or sometimes even lying down. Because of the natural drop in heart rate and blood pressure that occurs while sleeping, pooling of blood is not a problem when you are not awake.
Overall, the theory about Supine Hypotensive Disorder comes from the point of view that pregnancy is a medical condition, rather than a normal healthy condition. Having an innate "plumbing problem" that negatively impacted all human pregnancies certainly would not have stood the test of evolution over many millennia.
So rest easy in whatever position is most comfortable for you.
