Does sleep position affect sleep quality and health outcomes?

Does sleeping on your back during pregnancy really increase risks?

Yes, and the evidence is strong. In late pregnancy, sleeping on the back (supine) is linked to a higher risk of stillbirth and fetal growth restriction. One study of 187 pregnant women found that those with growth-restricted fetuses were far more likely to fall asleep supine (36.6%) compared to those with healthy-sized fetuses (7.5%) [1]. Another study showed that women who fell asleep supine spent 48% of the night on their back, versus 22.6% for those who started on their side [1]. This is why public health campaigns like 'Sleep on Side' have been launched in Australia and New Zealand. In a New Zealand survey of over 1,600 pregnant women, only 1.8% reported sleeping supine after the campaign, down from 3.9% in earlier years, and 65% had changed their sleep position based on advice [4]. However, the advice can cause anxiety: about 23% of women reported moderate-to-high anxiety about their sleep position, which may itself disturb sleep [2].

How does sleep position affect breathing and sleep apnea?

For people with obstructive sleep apnea (OSA), sleeping on the back makes breathing worse. In a study of 148 pregnant women in their third trimester, the apnea-hypopnea index (AHI, a measure of breathing pauses per hour) was 3.6 events/hour in the supine position, compared to 2.1 on the left side and 2.6 on the right [11]. Similarly, oxygen levels dropped more in the supine position [11]. This 'positional OSA' is very common: in a large analysis from the Sleep Heart Health Study (1,080 OSA patients), 62% had positional OSA, meaning their breathing problems were much worse on their back [3]. The good news is that positional therapy works: a study of non-apneic snorers who used a sleep position trainer to avoid supine sleep saw snoring severity drop from 8.0 to 7.0 on a 10-point scale, and bed partner satisfaction improved significantly [10]. However, one study found that people spend more time on their back during sleep tests (polysomnography) than during habitual sleep at home—14% more in lab tests—which can overestimate OSA severity for about one-third of patients [5].

Can sleep position affect your heart, shoulders, or eyes?

Yes, and the evidence is emerging. In the Sleep Heart Health Study (5,804 participants), people who spent more time sleeping on their back had significantly more angina (chest pain) episodes over 15 years of follow-up, even after adjusting for other heart risk factors [6][7]. For shoulder pain, one study of 115 patients found that the most common sleep position (fetus position, 39%) was linked to the highest rate of supraspinatus tendon problems (42.6% of all shoulder issues), though the link wasn't statistically significant [8]. For glaucoma, a small study of 40 patients found that sleeping on the right side was associated with a 1.8 mmHg increase in eye pressure and a 50% progression rate, compared to other positions [9]. These findings are preliminary but suggest that sleep position matters beyond just breathing.

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This answer is built on 11 peer-reviewed studies — published from 2018 to 2025, 5 from 2024 or later, 3 in Q1 journals, collectively cited 58 times — selected as the most relevant from 15 studies that passed quality screening, drawn from 78 papers retrieved from a database of over 500 million.

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