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How to Sleep During Pregnancy After Week 28: New CMAJ Recommendations
Last reviewed: 18.08.2025
">The Canadian Medical Association Journal published a brief but important review of sleep positions in pregnancy. The main conclusion: from the 28th week of gestation, it is better not to fall asleep on your back. Sleeping on your side (left or right) is associated with fewer risks for the baby, and simple techniques such as pillows or positioning devices can actually help reduce the time spent on your back at night.
What the research says
- The association “falling asleep on the back → risk” is supported by the meta-analysis. Compared with falling asleep on the left side, falling asleep on the back was associated with an increased risk of late stillbirth (adjusted OR 2.63; 95% CI 1.72–4.04). And when comparing “any non-supine position” versus “back”, the back was also associated with lower birth weight/SGA (OR 3.23; 95% CI 1.37–7.59).
- When it is especially important. Up to 28 weeks, no significant association with outcomes has been shown; after 28 weeks, recommendations to avoid the back when falling asleep become relevant. Moreover, the right side is as safe as the left.
- Why the emphasis on “how you fell asleep”. The position in which a person falls asleep determines a significant share of the night: if you lie on your back, on average about 50% of the night will be spent in the supine position; if you wake up in the morning on your back, a third of the night will probably already have been spent like that.
What can be done right today
- Fall asleep on your side (any side). If you do turn over during the night, don't be alarmed, it's normal; the important thing is to lie on your side again when you wake up.
- Use pillows. Regular or “pregnancy” pillows help reduce the time spent on your back to ~1 hour per night (≈13–16%). There is no panacea, but the effect is measurable.
- Positioning devices (from "somnology") are another option. In small studies, they significantly reduced supine time; in a large RCT, they showed no effect on birth weight, but as a way to reduce "spine" hours, they work.
For doctors and midwives
- Advise everyone, regardless of risk factors: after 28 weeks, avoid falling asleep on your back; the right side is acceptable. This is also consistent with the clinical guidelines for obstetric supervision.
- Communication - no intimidation. Focus on simple steps: "how you fall asleep" > "how you wake up", use of pillows/positional therapy, discussing sleep in appointments.
Important Disclaimers
- Most of the evidence is observational (associations, not causation in any particular case).
- RCTs on “hard” obstetric outcomes are few; the effect of devices on clinical outcomes has not yet been proven, although they do “shift posture”.
- The article discloses a conflict of interest for one of the authors (patent for a maternal sleep belt); this does not invalidate the results, but is important for transparency.
Conclusion
After the third trimester begins, it is better to fall asleep on your side - left or right. Simple means (pillows, positioning devices) help reduce the time spent on your back. This is an inexpensive, safe and practical strategy with potentially high benefits for the fetus.