Sleep is important for overall health. During pregnancy, finding comfortable and safe sleeping positions becomes more challenging as the body changes. Adapting sleeping habits throughout pregnancy supports both the pregnant individual’s well-being and the developing baby.
Understanding the Physiological Impact
As pregnancy advances, particularly after the first trimester, the growing uterus increases in size. Around 20 weeks of gestation, this enlarged uterus can exert pressure on major blood vessels in the abdominal cavity when a pregnant individual lies on their back. Specifically, the inferior vena cava (IVC), a large vein returning deoxygenated blood from the lower body to the heart, can become compressed.
Compression of the IVC reduces blood flow back to the heart, impacting overall circulation. The growing uterus can also place pressure on the aorta, the main artery carrying oxygenated blood from the heart to the rest of the body, though to a lesser extent. Studies show that lying supine in late pregnancy can reduce cardiac output by approximately 16% and decrease blood flow through the IVC at its origin by over 85%. This can lead to physiological changes for both the mother and the baby.
Risks to Mother and Baby
Compression of these major blood vessels can lead to several concerns for the pregnant individual. Symptoms like dizziness, lightheadedness, nausea, and shortness of breath can occur due to reduced blood pressure, a condition sometimes called supine hypotensive syndrome. This happens because the heart receives less blood to pump, leading to a drop in systemic blood pressure. These maternal symptoms typically arise within 3 to 10 minutes of lying supine.
For the baby, reduced blood flow and oxygen delivery can impact fetal well-being. Compression of the aorta can decrease blood flow to the placenta, potentially leading to lower fetal oxygen levels and reduced nutrient supply. Research suggests an association between back sleeping in late pregnancy (especially after 28 weeks) and an increased risk of complications such as reduced birth size and stillbirth.
Safe Sleeping Positions
To mitigate risks, healthcare providers recommend sleeping on the side, particularly the left side, during the second and third trimesters. This position optimizes blood flow to the uterus, placenta, and the developing baby. Sleeping on the left side also aids kidney function, which can help reduce swelling in the legs, ankles, and feet.
While the left side is preferred, sleeping on the right side is also considered safe. The goal is to avoid prolonged periods on the back.
Practical Tips for Side Sleeping
Transitioning to side sleeping can be challenging, especially for individuals accustomed to sleeping on their back. Using pillows provides significant support and comfort. Placing a pillow between the knees helps align the hips and spine, reducing pressure on the lower back. A small pillow or rolled towel tucked under the belly can offer additional support.
Full-body pregnancy pillows are designed to support the head, belly, back, and knees, helping maintain a side-sleeping position. If an individual wakes up on their back, they should simply reposition onto their side. Placing a firm pillow behind the back can also serve as a gentle reminder to stay on the side and prevent rolling over.