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 In Ask an Expert, Midwifery, OB/GYN & Women's Health, Pulse Blog

Q: What sleep position is best during pregnancy?

Many people are told to only sleep on their left side during pregnancy—advice that can cause non-side-sleepers some anxiety. Getting enough sleep during pregnancy is already difficult given the number of trips to the bathroom, overheating, and general back and pelvic aches and pains. So where does this recommendation come from?

One of the body’s largest blood vessels, the aorta, runs down the back behind the uterus. Theoretically, when a pregnant person is lying flat, the weight of the uterus (and baby) could compress the aorta and other blood vessels and limit blood flow to the uterus, placenta, and the rest of the body. Some people might notice feeling light-headed or dizzy when lying flat on their backs. This is a clear sign of limited blood flow. Medical providers have worried that if blood flow is restricted to the placenta for long periods of time, it could impair babies’ growth and increase stillbirth rates. But does evidence support that back-sleeping can cause these bad outcomes? Not really.

There isn’t data to suggest that sleep position (back, stomach, or right or left side) affects babies’ growth or impacts pregnancy outcomes—at least up until 28 to 30 weeks of pregnancy. A 2019 NIH-funded study surveying more than 8,700 pregnant people found no association between sleep positions and poor pregnancy outcomes before 30 weeks of gestation.

After 30 weeks, some evidence suggests that back sleeping could modestly increase the chance of having a small baby or experiencing a stillbirth. However, evidence for this association is limited. Many of the studies contain flaws. For example, researchers collected sleep-position data from parents only after the poor pregnancy outcome had already occurred, or they drew conclusions based on a very small number of patients. Clinicians are still waiting for a well-designed, large-scale study to investigate third-trimester sleep positions and pregnancy outcomes.

Given the possible link between back sleeping and poor pregnancy outcomes, I recommend using a pillow to create a slight side tilt when sleeping on the back. That said, those who wake up on their backs shouldn’t panic. Simply readjust.

Tips for sleeping comfortably

Some people who struggle with sleep during pregnancy may find the following tips helpful:

  • Create a bedtime routine that promotes relaxation. This might include a warm evening bath, a sound machine with soothing background noise, or lavender essential oils. Avoid phones and TV right before going to sleep.
  • Support pelvic alignment by placing a pillow between the knees and ankles.
  • Use a small pillow or rolled-up towel under the waist (in the space between the ribcage and hip) to relieve hip and spine pressure while side sleeping.
  • Place a small pillow or rolled-up towel between the knees and actively squeeze it when rolling from one side to the other or when standing up from bed in order to combat pain in the front of the pelvis.
  • Keep heartburn in check by propping the head up with lots of pillows. Decrease fatty and acidic foods in the evening and ask your clinician if it’s time to start medications to decrease stomach acid.

—Alex Silverman, CNM

Midwife Alex Silverman empowers individuals to make informed choices about their bodies. She takes the time to educate patients about evidence-based options and supports them as they choose the best course for themselves and their families.

Alexandra (Alex) Silverman, CNM.