Yoga teachers often caution their pregnant students not to lie on their back or on their right side, believing that it may be harmful to both mom and baby. Is this kind of fear warranted? We’ll break down the science and anatomy behind this advice so that you can have the knowledge to empower your students. And hopefully this will help change the culture of fear around pregnancy, especially around pregnancy and yoga. Yoga should give pregnant women the tools to manage their stress, not create additional anxiety.
The reason pregnant women are cautioned against lying on their back or their right side is a condition known as supine hypotensive syndrome (SHS). SHS arises from the compression of the large abdominal vein that returns blood to the heart. The incidence of SHS is relatively low. The medical literature reports an average of 8% of pregnant women reporting symptoms of SHS when they are lying on their backs.
The highest rate of SHS is during week 38 of pregnancy. After this time, the fetus drops into the pelvis as the fetal head begins to engage, lessening the pressure on the back of the abdomen. Women in labor do not experience SHS, even when they are lying on their backs.
The danger of suffering ill effects from SHS is extremely low because most women experience discomfort and shift into a more comfortable position long before the condition escalates. So even the 8% who report symptoms don’t often suffer any long-term effects.
This means that a woman who pays attention to her body and does what ‘feels right’ will act in a way that is healthy for herself and her unborn child. However, we live in a culture that often fosters an atmosphere of fear around pregnancy and delivery. Many doctors will even recommend that women not lie on their backs as early as 20 weeks into their pregnancy. Fear-based advice does not encourage pregnant women to connect with their own bodies for wisdom and guidance. Here we’ll look at the facts of SHS and what it means for a pregnant woman in your yoga class.
The anatomy and biology
The large vein that returns blood from the legs, pelvis and abdomen to the heart is called the inferior vena cava (IVC). In most people, the IVC lies slightly to the right of midline against the vertebral bodies. The aorta, the large artery, lies to the left. Unlike the aorta, the IVC does not have smooth muscle its walls to support the integrity of the structure, making it more susceptible to compression.
When a woman in late pregnancy lies on her back, the weight of the uterus and fetus can compress the IVC. Although compression is fairly common, most women have healthy circulation that allows blood to return to the heart via alternate veins.
Women with one or more risk factors (obesity, an excess of amniotic fluid, uterine fibroids, diabetes or 2+ fetuses) may develop nausea, paleness, darkness in the hands and feet and increased heart rate within 3-10 minutes of lying down. Noticing these symptoms, most women will immediately sit up or shift position, which removes the pressure from the IVC. Once the compression of the IVC is alleviated and normal blood flow returns, the symptoms disappear.
Preventing SHS Symptoms
There are simple ways to prevent the onset of symptoms from SHS, which you can offer your students during class. The first thing to remember is that if a woman feels comfortable lying on her back, then there is no reason why she shouldn’t. If she does experience any type of discomfort, whether it is from SHS or generalized back/hip or other types of pain, then alternative positioning should be sought. Here are some suggestions that will effectively remove pressure from the IVC:
1. Elevate the head and shoulders about 30 degrees from the floor
2. Bend both knees and place the feet on the floor
3. Place a blanket or pillow beneath the right hip
4. Lie on the left side instead of on the back or the right side
As yoga teachers, we are obviously concerned with the health and well-being of our students. We often err on the side of caution when making recommendations to our students, especially our pregnant students. The fact is, the human body is really excellent at pregnancy, labor and delivery, and there is very little a typical yoga class can do to negatively affect that process (hot yoga is one scenario that can be dangerous). Encourage your students to follow the wisdom of their own body. And little by little we can work to dispel the culture of fear around pregnancy and empower women with their own strength and wisdom.